# Battery Discharge during very cold weather, Emergency Start Procedure logic



## Ekremsky (Sep 8, 2010)

Hi,I came accross very strange situation:
My car is eating up battery power: only when outside is cold,below 10 C,something very strange,
in summer days there is no battery draining,my clima stays adjusted at 19 C,but now is very cold and I make it 25 C,and then it is the mystery: the battery is drainig for 2-3 hours below 10V?
I made some tricks:
-when the car i turned off while clima is set to 25C(or above 24C)-the battery is drainig very fast,second battery relay switches on and I can turn the ignition on only with the key in!
-when the car is turned off while the clima is set to 18C(or below 24C) the battery drain is very small???
So does something turn on while the car is locked,or something is trying to keep any temperature inside?
I double checked if AUX heating is off,and it is off,I dont have parking heater or anything.
Another thing I notice is when I turn on the rear seats climatronic above 24C the voltmeter goes from 14V to 13V and stays there for a 5-10 min,if I turn off the rear seats climatronic or set it below 24V the voltmeter gets back to 14V?

Any ideas whats is happenig with the car?


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## Paximus (Aug 26, 2011)

Hi,

It sounds like the electric additional heating elements warming the air to the rear seats are staying switched on too long.

Or, the residual heat pump is not switching off.

Do you have residual heat function turned on on the central display?

Cheers,
Chris


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## Ekremsky (Sep 8, 2010)

*battery drain*

Hi,
I don't have residual heating in my car,as you say there is something that stays turned on too long time and eats the battery.I think it could be the heating elements under the front seats,as far as know there are that kind of heaters under the seats,or may be the thermo relays on the passengers side that turn the heaters on,or .. may be the climatronic control module is defective?
Don't know,when I scan with VCDS there is no error in the HVAC module.

Regards,
Ekermsky


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## WillemBal (Nov 20, 2010)

Ekremsky said:


> ....but now is very cold and I make it 25 C,and then it is the mystery: the battery is drainig for 2-3 hours below 10V?


Assuming this is happening when your engine is running and perhaps you are driving as well, this is not normal. But I assume you are driving. Perhaps you can clarify whether you are just sitting in the car with ignition on, engine off, engine on and idle with gear selector in Park position, or whether you are driving.



> I made some tricks:
> -when the car i turned off while clima is set to 25C(or above 24C)-the battery is drainig very fast,second battery relay switches on and I can turn the ignition on only with the key in!


This could be the result of a weak LH battery. You simply cannot turn off the engine and turn the heater on at 25C when it is that cold outside. Your rear heater system will switch on the NTC heater which absorb a LOT of energy. Perhaps 50 to 100 Amps to create some significant amount of heat in the back of the car. This will quite rapidly drain your battery and after a while, the instrument cluster will tell you that it is switching off electrical consumers. When you still continue, your Phaeton will notice a crippled state of the battery and beg you to switch on the engine. When you miss that message, or ignore it, then the only way to start is with the "emergency procedure".



> I double checked if AUX heating is off,and it is off,I dont have parking heater or anything.
> Another thing I notice is when I turn on the rear seats climatronic above 24C the voltmeter goes from 14V to 13V and stays there for a 5-10 min,if I turn off the rear seats climatronic or set it below 24V the voltmeter gets back to 14V?


With a temperature set to 24 ⁰C with cold outside temperatures, you will force the HVAC to switch on the rear heaters to 100%, with a very high electrical load as result. My car is doing exactly the same. Voltmeter is normally just below 14 Volts (13.8) and it will drop to 13.3 Volts when I switch on the rear HVAC. For that reason, I ALWAYS switch off the rear HVAC as soon as I've started the engine.

The voltage can in fact drop below 12.7 Volts when the engine is running and when many electrical consumers are switched on, like light, HVAC, and or rear window heater.
The 12.7 Voltage limit is considered as "critical" by the system (Central Electrical System Controller) which will then instruct the ECU (Engine controller) to increase idle speed.
When the voltage (with engine on) drops below 12.2 Volts, the situation is so critical that the system will start switching off consumers.

Willem


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## n968412L (Apr 23, 2009)

WillemBal said:


> When you still continue, your Phaeton will notice a crippled state of the battery and beg you to switch on the engine. When you miss that message, or ignore it, then the only way to start is with the "emergency procedure".


Willem - can you just confirm this statement? I thought we had established some time ago that the emergency start will work for when the RH battery is unserviceable - ie by using the LH battery to crank... but that it does not work the other way round. In fact if the LH battery is US, then there isn't even the power to work the battery paralleling relay. Or have I still misunderstood this....

Thanks

Mike


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## Paximus (Aug 26, 2011)

VW is adamant that the car can be started with either battery fully discharged, although that doesn't seem to agree with our experiences. There must be some other factor at work.

Chris


*Cranking Power Flow diagrams for flat left 
and flat right battery* (click for full size)


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## WillemBal (Nov 20, 2010)

n968412L said:


> Willem - can you just confirm this statement? I thought we had established some time ago that the emergency start will work for when the RH battery is unserviceable - ie by using the LH battery to crank... but that it does not work the other way round. In fact if the LH battery is US, then there isn't even the power to work the battery paralleling relay. Or have I still misunderstood this....


Hi Mike,

You are right in your assumption that the emergency start procedure won't work when the LH battery is completely drained. Electronics, especially car electronics, are designed to work with a wide voltage supply. I estimate that the lower limit is near 9 Volts, a level which is well below a drained battery. Relays then still can be energized, as the "make" voltage is about 2 third of the rated voltage and the "hold" voltage is about one third of the rated voltage.
So once the LH battery voltage drops below say 9 Volts, the battery is too much drained to start the engine in emergency mode.

There is a very good thread by Michael, explaining the load shedding procedure and how the instrument cluster informs the user about its actions:
Intervention Load Management on the Phaeton 
Unfortunately, load shedding only applies to components which are designed to heat something, and dome/trunk lights. All 30+ controllers will remain active and will continue to drain the LH battery at a rate near 20 Amps, even after the final warning has appeared near 11 Volts: "Please start engine". The voltage will, by then, drop pretty quickly because that is exactly what a 0% charged battery will do. And it will ruin the battery of course. With a (ruined) battery voltage of say 5 Volts, there is no way to start the engine by means of the emergency start procedure. 

The bottom line is: when you don't do what you are told, i.e. properly respond to the message "*Please start the engine*", the battery will further drain, destroy itself and the controllers will slowly enter a state of coma, hence the patient is no longer capable to ask for help and to enter the emergency start mode.

Willem


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## Paximus (Aug 26, 2011)

Hi Willem,

I wonder if this is related to the KESSY power FET problem that you have some success in repairing?

According to the simplified diagram above there are two power supply inputs to the KESSY, one from each battery (one direct from the left battery, one from the right battery via Terminal 30SV through Relay S). Do you think it is possible that one of the power inputs can stop working, so that although the car can start in normal circumstances, the emergency start procedure described in the SSP cannot work because the power path from the starter battery is open circuit?

Chris

_*Archival Note: * Discussion of the KESSY power supply MOSFET repair referenced in the first paragraph can be found at these two threads:_

Repairing the Access and Start Controller (controller 07) - resolving antenna 'open circuit' faults
Yellow Key Symbol on Combi Instrument Panel (KESSY photos and troubleshooting)


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## Ekremsky (Sep 8, 2010)

*battery drain*

Don't know,I changed the battery last year with original one from VW Germany,every year when the temperature drops,I have the same problem - very fast battery drain ((

Ekremsky


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## jyoung8607 (Feb 14, 2006)

WillemBal said:


> You are right in your assumption that the emergency start procedure won't work when the LH battery is completely drained. Electronics, especially car electronics, are designed to work with a wide voltage supply. I estimate that the lower limit is near 9 Volts, a level which is well below a drained battery. Relays then still can be energized, as the "make" voltage is about 2 third of the rated voltage and the "hold" voltage is about one third of the rated voltage.
> So once the LH battery voltage drops below say 9 Volts, the battery is too much drained to start the engine in emergency mode.


I think the battery monitoring controller operates those relays, and it always has direct connectivity to both batteries. So, if it needs to operate the paralleling relay or either of the switchover relays, it has power available so long as ONE of the two batteries is in decent shape. This is reinforced by VW's recommendation of jump starting using the starting side of the electrical system rather than the VPS side. Jump starting wouldn't be necessary if the VPS battery were charged, it can be paralleled in to start.

So, I think the battery controller can energize terminals 15SV and 30SV using best available power at the appropriate time, and that takes care of control system needs. The question is, how does it know when to wake up? If it sits there and monitors voltage 24x7x365, it's a parasitic drain, and energizing the normally-open start battery switchover relay would be an even bigger one. So, it's got to be staying asleep until triggered by an external event.

The VW docs say key-in-ignition. This means one of two possible things:

1) KESSY has constant power available from the start battery as well as the VPS battery, and can wake up using that if triggered. If it senses poor VPS voltage, it triggers emergency mode on the dedicated wiring harness pin, the battery monitoring controller wakes up, the start battery switchover relay is triggered and start relevant stuff is now powered.

2) There is a contact switch in the ignition key cylinder which goes back through the vehicle main harness directly to the battery monitoring controller. It wakes up on its own and handles power-up of start relevant equipment.

I believe it works like #1 above, but it's been a while since I read the wiring diagrams. 

Jason


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## Paximus (Aug 26, 2011)

> parasitic drain


I think it is plausible that any controller is 'apparently' awake 24/7, or at least going through a wake/sample/sleep cycle every hundred or so millisecs. For example the air suspension draws a smoothed average of 200 microamps doing this all day 24/7 while it is in full vehicle sleep mode.

And to do this at any arbitrarily low battery voltage such as 5V it's normal (if that's a requirement) to use a DC-DC inverter for part of this fast process.

Chris


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## WillemBal (Nov 20, 2010)

jyoung8607 said:


> So, it's got to be staying asleep until triggered by an external event.
> 
> The VW docs say key-in-ignition. This means one of two possible things:
> 
> ...


Guys,

I couldn't stand it any longer and just tried what I meant to do for a long time. I opened the front door and the trunk, disconnected the LH battery and did my experiments.



With key in pocket, I pressed the brake pedal. Nothing.
Then I pressed the start button, still nothing.
I tried a couple of times more, with/without foot on brake pedal, pressing firmly on the start button, but still nothing.
Then I put my key in the key cylinder (I guess it was the first time I ever did so )
Turned it to the right as designed. Guess what... the instrument cluster comes alive!eace:
Next, I spotted the *yellow key* symbol, accompanied by the text : "System Fault Workshop"
Turned the key back and tried once more - no start.
Next, I turned the key all the way to the left, through the neutral position, until it didn't go further.
Then I turned the key back to ignition on position: still the same message.
And then I turned the key to start position: the engine started! 



Just when the car started, I immediately switched on the lights, which kind of hesitantly came to life. Meanwhile, I looked at the dash panel voltmeter, which showed the same kind of behaviour as with connected LH battery - business as usual. When it almost had reached 14 Volts, I switched off the engine.
All dome lights were functional after switching off the engine. I got out of the car to reconnect the battery. Even the trunk interior lights worked. I think this all lasted about 15 seconds after switching off the engine.

So it looks like Jason's hypothesis #2 is valid. I guess we need to check with the wiring diagram to see what happens when the key is used to start the engine. Anyway, I think it is remarkable that the instrument cluster already lights up even before initiating the emergency start procedure.

Anybody who knows the answer may stick up his finger. 

Willem


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## Paximus (Aug 26, 2011)

Hi Willem,

That's magnificent work! You are very brave (or very rich)! I am glad that you had the courage to solve the question! :thumbup: :thumbup:

I had a look at some diagrams. The Battery Management controller is the key to the emergency start procedure, as you would expect.


The Battery Management controller has permanent direct voltage feeds from both left and right batteries, naturally, so it's powered 24/7

The Battery Management Controller sends a 'Start-Relevant' power feed (Terminal 15SV) to the KESSY, so there's no problem in the KESSY being kept powered up regardless which battery is flat

The ignition key PCB sends 6 wire outputs into the KESSY apart from its input wire and the transponder reading unit wires and the lock magnet wires, so there's no problem with the KESSY getting a key-in signal

The Battery Management Controller also sends a direct power feed signal to the In-Dash Panel, which might explain how it can come alive during emergency start

But the problem is I can't yet see how the KESSY is powered up before the ignition key is inserted, so that it can detect the key and tell the Battery Management controller that an Emergency Start is required, unless it's also powered 24/7 even with the Vehicle Power Supply not working. Somehow!

Chris


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## WillemBal (Nov 20, 2010)

Paximus said:


> ...That's magnificent work! You are very brave (or very rich)!


Chris,

I figured that it might have been one of the validation tests during the design of the Phaeton. It is an easy test and when it would not have been successful during validation, it would not have passed particular design criteria with respect to starting the engine with one of the two batteries drained or absent. Perhaps it was one of the 10 secret design criteria.



> I had a look at some diagrams. The Battery Management controller is the key to the emergency start procedure, as you would expect. The Battery Management controller has permanent direct voltage feeds from both left and right batteries, naturally, so it's powered 24/7


The BM controller needs to be connected to both batteries for the purpose of monitoring the batteries. 



> The Battery Management Controller sends a 'Start-Relevant' power feed (Terminal 15SV) to the KESSY, so there's no problem in the KESSY being kept powered up regardless which battery is flat.


As additional functionality, it MAY forward the two battery voltages by means of an OR/OR circuit, which in its easiest form is composed of two diodes, anodes to each battery, cathodes tied together. This would then be terminal 30SV, not 15SV.



> The ignition key PCB sends 6 wire outputs into the KESSY apart from its input wire and the transponder reading unit wires and the lock magnet wires, so there's no problem with the KESSY getting a key-in signal


Correct, it is E415, the Access/Start Authorisation *Switch* which indeed has 6 select lines. Not to be confused with E408, the Access/Start Authorisation *Button*, which is not taking part in the emergency start process (at least not when the LH battery is drained, empty or absent)



> The Battery Management Controller also sends a direct power feed signal to the In-Dash Panel, which might explain how it can come alive during emergency start.


Almost. I think you are referring to connection B449, which is the Emergency Operation Connection.
It is a permanent wire link between the BM controller J367 (pin A15) and the Access/Start controller module. It is ALSO connected, as you indicated, to the connection "Notbetrieb" (=Emergency Operation) of module J285, the instrument cluster (Control Module with indicator unit in instrument panel insert)


> But the problem is I can't yet see how the KESSY is powered up before the ignition key is inserted


The KESSY apparently always has power via the Emergency Operation Connection as indicated above. 




jyoung8607 said:


> I think the battery monitoring controller operates those relays, and it always has direct connectivity to both batteries.


In the case of the missing LH battery, the Switch Over Relay J580 is powered from pin A16 of the BM controller and the other side of the relay coil is connected to terminal 30. And this is where it becomes fuzzy. In the case of a missing or drained LH battery, the terminal 30 won't be 12 Volts. So when pin A16 is pulled to zero by the BM controller, the coil will be connected to two ground potentials and thus won't trip. It is possible though, that pin A16 is going to +12 Volt instead, so relay J580 trips. It is also possible that relay J580 responds to specific conditions, i.e. contains some basic electronics, which decide whether the relay should be energized, based on the present voltages to which it is connected, i.e. the voltage state of al the terminal 30's to which it is connected. It is not a an ordinary relay, which is already visible in the wiring diagram; its symbol is different than the symbols used for other relays.


> So, I think the battery controller can energize terminals 15SV and 30SV using best available power at the appropriate time.


Right. Terminal 30SV is 12 Volts after initiating the emergency start procedure because then relay J580 is active. From that moment on, the situation exists as per the left diagram of the emergency start document which Chris posted earlier.



> The VW docs say key-in-ignition. This means one of two possible things:
> 1) KESSY has constant power available from the start battery as well as the VPS battery


Yes, either directly from the LH battery or via the Emergency Operation Connection.



> ..., and can wake up using that if triggered.


Yep. Turning the key to the right wakes up the KESSY and the Instrument cluster and gives a warning to the user. Not sure whether the CAN controller then comes to live already.
Turning the key to the left, causes the KESSY to send a signal to the BM controller, which in turn causes J580 to be energized, so that al start relevant controllers are armed. Terminal 30SV then is 12 Volts. The LH battery is isolated from the system. The system now is prepared (for only a limited time period, perhaps 15 seconds) for starting the engine in emergency mode.

If the user does not respond, J580 will hopefully disconnect, avoiding further drain of the only available power source, the RH battery.

Willem


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## Paximus (Aug 26, 2011)

Today we have concentrated on how to turn on the ignition switch.

Tomorrow perhaps we will address the functioning of the Mars Lunar Vehicle! 

Chris


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## WillemBal (Nov 20, 2010)

So here are some photo's of the entire Emergency Start Procedure. I couldn't resist repeating my experiment and leave the car running for a bit longer time, just to see what voltage the dash panel voltmeter would indicate after starting the engine.

As explained in one of my previous posts, the first 4 steps basically didn't wake up the car. The first sign of life appeared after inserting the key in the keyhole and turning it to the ignition position (Step 5):










This was followed, within 15 seconds, by a reduced message:










I think that the color indicates that there is a problem, which can be solved by looking in the manual. I guess it indicates that the emergency start procedure must be followed. And else, RTFM...

So I turned the key to neutral position, then to the left, until the stop (Step 8). Next, turning the key to the ignition position again, gave this scaring view:










As you can see, all the normal lights are now lit. The red colour of the message gives the impression that one should immediately call a dealer. But of course, I didn't. The German engineers would never have designed a car which destroys its own components by doing something simple as turning a key. So I turned the key a little further, which started the engine. Voltmeter behaved as usual. After 1 minute with the engine on, I took this picture:










Dash panel meter sitting nicely at 14 Volts, just a little more nervous than normal, caused by the absence of the LH battery, which otherwise forms a constant and smoothing load.

After shutting down the engine by pressing the start/stop button (key still in ignition position), gave the following view:










After taking out the key, the car simply died again. I then reconnected the LH battery, closed the trunk by pressing the button twice, started the engine as usual, which gave the usual faults like suspension failure, ESP light and the adaptive cruise control greyed out.










To clear the last error message, all that is needed is to stop the car, then restart again:










After that, I must say that I needed to re-adapt the windows to allow fast close/open. And to re-adjust the clock, which had moved to 12:00 PM.

Willem


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## WillemBal (Nov 20, 2010)

Paximus said:


> Today we have concentrated on how to turn on the ignition switch.
> Tomorrow perhaps we will address the functioning of the Mars Lunar Vehicle!
> Chris


Chris, that will be a piece of cake for us now! :laugh::laugh::laugh:


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## WillemBal (Nov 20, 2010)

n968412L said:


> Willem - can you just confirm this statement? I thought we had established some time ago that the emergency start will work for when the RH battery is unserviceable - ie by using the LH battery to crank... but that it does not work the other way round. In fact if the LH battery is US, then there isn't even the power to work the battery paralleling relay. Or have I still misunderstood this....


Mike, does this answer you question?


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## PanEuropean (Nov 3, 2001)

Wow, this is an awesome discussion! I can't remember the last time I learned so much new and useful information in such a short period of time.

Michael


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## Paximus (Aug 26, 2011)

It's such fun testing when something isn't actually broken!

Willem, was the icon in this photo (after the car was running OK on one battery with 14V) still the yellow key symbol, or something else? I can't quite make it out.










Presumably all the other warnings after the engine started were because in Emergency Start only the controllers required for starting are powered on (according to the SSP). That would exclude Suspension, TPMS, HVAC and so on.

Chris


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## WillemBal (Nov 20, 2010)

Hi Chris,

The yellow symbol you can see in that picture, at the top of the instrument cluster is the suspension fault symbol. I'm sorry for the lack of sharpness. I guess that I was so excited that I was shaking from sheer agony. 

Willem


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## Paximus (Aug 26, 2011)

Ah, thanks.

It's surprisingly hard to get a clear photo of the dash, you just get it in view and the steering wheel moves out and knocks you off position!

Chris


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## jamescardinell (Jan 15, 2013)

*Possible cold weather start issues?*

Hi guys-
I've been a longtime follower of some of the columns but haven't posted since I picked up my Phaeton in September of '12. I bought a 2006 4.2 V8 from a dealer in Las Vegas, and it's been an amazing vehicle. I've driven a lot of ridiculous cars over the years and I don't think any of them matched the driving pleasure of this thing. I've had a couple issues that I'm resolving with it (all part of lovingly bringing a car with 75K+ mi on it up to speed) but this one from the other day has me perplexed:
The weather in the SF bay area has been quite cold for California, hovering around 36 deg F i the morning, though I know that isn't cold at all compared to most place in winter. The last three days my car computer has been resetting itself in the morning when I come out to take it to work. The analog clock resets itself to 12:00 and I have to change it in the in-dash screen, and the engine doesn't turn over half of the time. It's not tracking the last trips in the computer history either. I've had to use the key to manually open the drivers door since it's not communicating with the FOB, and then use the emergency start procedure to turn the engine over. Is this anything anyone has experienced? I'm taking it into the dealership in the morning, but as nice as they are, I really feel like they don't entirely understand the quirky nature of the vehicle. Most of the techs there (even the "Phaeton trained" ones) haven't worked on the cars barely at all. To the best of my knowledge theres only a few of them in the area so the chances of them getting to know the vehicle intimately are slim to none...

Thoughts?


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## Paximus (Aug 26, 2011)

Hi James,

Welcome to the forum! Yes, it's a 'ridiculous' car (but fortunately _Ridiculus_ was the Roman god of Safe Return...!)

Clearly the battery system is low at startup. It could be the right (starter) battery, in which case the extra drain on the left (vehicle power supply) battery might be stopping the clock etc. Or it could be the left (vehicle power supply) battery, in which case the ignition key wouldn't work until you did the right-left-right trick to parallel them both.

So either (a) one or the other (or both) of the batteries are failing, or (b) the battery controller is not functioning correctly, or (c) the alternator is not charging sufficiently, or (d) something is draining the battery overnight.


(a) Check the left battery date, often stamped on the -ve post. If it's 5 years old or more it is running on empty. Because of the issues, use only the correct OEM replacement part. The right battery usually survives a long time, because it is run under pretty much perfect conditions. It's less helpful to charge the batteries and 'try again' because this doesn't really help the diagnosis much, other than to confirm that you are eventually getting low voltage, which you knew to begin with.

(b) If you have a VCDS scan to hand check the part number of the battery controller. If it is suffix B it needs replacing. In any case a scan might help, and most enthusiastic owners find that buying a VCDS (VAG-COM) cable recoups its cost over and again. This is by explaining to the dealer what is actually wanted and keeping the diagnostics charges under control.

(c) Check that the battery voltage dial on the dash reaches 14.0 volts after some decent running. If it does then the alternator is probably OK.

(d) This is more difficult to check. It's usual to do the others first. Measuring the battery drain requires a DC clamp milliammeter (which is not a common piece of test kit) and strictly following a certain procedure.


I hope that helps!

Regards,
Chris


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## vwgeorge2 (Mar 24, 2008)

This is a very good thread! Very detailed etc...

My car just started acting up? temps are around freezing daily at the moment.

Car goes to sleep at night, alarm stops flashing etc. I open the door with the key and the car will not start... So I turn the key full left and then back to the right and the car starts fine etc. The clock spins to recover the correct time and the volt meter rises back to 14 volts immediately.

So what battery do you think is going bad?

Bill


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## invisiblewave (Sep 22, 2008)

That's the LH battery. When the RH battery is failing, you don't need to do the emergency start procedure, it automatically parallels the batteries for you. The emergency start procedure parallels the batteries to allow the electronics to run from the starter battery when the LH battery doesn't have the juice.


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