# 2006 Audi A3 dead temp gauge after new sensor install.



## 16vsilverstreak (Dec 5, 2001)

Just picked up a 2006 A3 2.0t 87,000 miles 6 speed with three pedals. Day one. Got it home, left rear window will not go up, ended up being high resistance on window guides nothing broke. Lubed guides window back in operation. Day 2. didn't drive it due to window. Day 3. Temp gauge dies on the way to work. On the way home from work it throws CEL. Day 4. Replace coolant sensor, gauge still dead along with CEL. My one year old VAD modile wired cable is worthless on CAN BUS vehicles. VAD doesn't have swap out program like Ross. Still on the fence about going to Ross or staying with VAD. Anyway, is there anything else that would cause failed temp gauge besides faulty wiring? I'm heading to the Advance to pull codes and see if gauge will come back with cleared DTCs. Homelink is currently inoperative. I miss my high mileage Golf MKIV.

Update: Coolant System performance DTC, cleared. Temp gauge operational.


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## SilverSquirrel (Jul 24, 2006)

If it happens again (and again) that DTC indicates a weak thermostat. 

Replace it and u will b ok


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## bikedewd (Jan 26, 2007)

That sounds exactly like what I am going through. I just replaced the temp sensor, but my guage is still dead. Are you saying that clearing the codes -- I guess disconnecting the battery? -- brought the gauge back after you replaced the sensor?

Thanks!


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## mike3141 (Feb 16, 1999)

Clearing the codes will make the temp gauge work again--until the engine coolant sensor throws another code......


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## callmecue (May 18, 2007)

Was about to research and/or post another thread about the same issue. Replaced my sensor a while ago after dead guage. I have VAGCOM and have been having to diagnose and clear faults way too often. First, the guage will die, then it will throw a CEL some time later. Will definitely try replacing the thermostat soon. Any other tips are much appreciated.


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## SilverSquirrel (Jul 24, 2006)

ive been through this and posted at length. search for my threads.

Heres what is happening.

1. BOTH ECT ENGINE COOLANT TEMPERATURE SENDERS ARE OK.

2. The very smart and sneaky ENGINE MANAGEMENT COMPUTER (ECU) calculates how fast the car is warming up, based on ambient temperature (how hot or cold it is outside) and how much fuel and air is being burned by the engine, using the MAF sensor, and checks this with how quickly the ENGINE COOLANT TEMPERATURE rises. The engine is programmed to operate in a VERY narrow temperature range, for emissions reasons. 

3. IF for some reason, the smart computer doesnt think the car is warming up as fast as it should be, a COOLANT PERFORMANCE MALFUNCTION fault code will be recorded. This can only be read by a VAG COM or other compatible "scanner", but as a special treat, If your instrument cluster temp gauge works via the can bus and recieves its data from the ECU, and not directly from the ECT, as in the 2006 A3 3.2 VR6, engine code BUB........wait for it.....

*YOUR TEMP GAUGE WILL PLAY DEAD! * 

4. If this happens a second time, then you will get a yellow light on your insturment cluster, indicating a an engine malfunction. Then you check the codes and find out whats up, only to be confused as to why your gauge died.

5. As soon as you clear the fault code with your VAGCOM etc, your temp gauge will spring to life (if engine is warm). BTDT seen it with my own eyes, brother.

I suppose a faulty ECT sender could cause a coolant performance malfunction, but far and away the most common cause is a worn out* THERMOSTAT*, which is a little spring operated valve, that opens when the spring gets to a certain hot temperature, and sends engine coolant flow to the radiator to chill out. When the spring wears out, is gets weaker, and opens TOO EARLY, causing the car to take longer to warm up. This pisses off the ECU, who then tells your temp gauge to play dead.

This seems to be undocumented, and as to which engines in what cars play this game, who knows. but check your wiring diagrams, its easy to see what makes the temp gauge wiggle.


:wave:


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## 16vsilverstreak (Dec 5, 2001)

This needs to be in the A3 FAQ.


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## bikedewd (Jan 26, 2007)

Thanks for the detailed explaination SilverSquirrel! My guage is now working again after clearing the codes -- no surprise, huh? -- and I'll see if I have another issue. If so, thermostat time!


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## tony a3 (Jul 31, 2010)

SilverSquirrel said:


> ive been through this and posted at length. search for my threads.
> 
> Heres what is happening.
> 
> ...


Weird, I am LEGIT going through this right now! Dead gauge, CEL light, shop replaces the 'bad' sensor, get about 5 miles out, gauge drops and appears inop again. Thanks for the insight, going to have the shop change out the t-stat tomorrow.
:beer:


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## GGVDub (Apr 8, 2004)

I had this same thing happen with my 06. Luckily I'm under a warranty, but the dealership said its a bad sensor in the cluster. They replaced the entire instrument cluster for that one sensor. Seemed a little extreme, but it works now.


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## srbeards (Oct 26, 2010)

I had the same issue with my 06. Temp gauge would not rise. It happened intermittently at first, but then it would just not work. Replace the coolant sensors, which didn't fix it. Eventually I got in and replaced the thermostat and it worked great. It's nice that the faulty 'stat gets stuck open instead of closed.


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## Travis Grundke (May 26, 1999)

I think we can add the thermostat to the list of items that are pretty much guaranteed to fail on the A3. My '06 is at about 89,000 and the thermostat began failing about 5,000 miles ago.

I'm half expecting Audi to put an extended warranty on the thermostat like they have with the PCV and the cam follower/HPFP. 

Anyone have any cost estimates for the thermostat replacement? I know it's a PITA due to its location.


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## SilverSquirrel (Jul 24, 2006)

Travis Grundke said:


> I think we can add the thermostat to the list of items that are pretty much guaranteed to fail on the A3. My '06 is at about 89,000 and the thermostat began failing about 5,000 miles ago.
> 
> I'm half expecting Audi to put an extended warranty on the thermostat like they have with the PCV and the cam follower/HPFP.
> 
> Anyone have any cost estimates for the thermostat replacement? I know it's a PITA due to its location.


Well, its not that the thermostat fails. It will still do 90% of its job. You still get a warm engine, and cabin heat works, and the car does drive and isnt overheating.

They just get a little weak, not stuck. The big issue is that the software is extremely sensitive to even 5% slow warmup, worried that there might be a wee bit extra evil greenhouse gas slaughtering the rainforrest or some other nazi tree hugger nonsense. 

Im pretty sure the thermostat itself is the same quality as any other. In the old days, a fresh thermostat was part of normal maintainance along with a coolant flush. 
:snowcool:


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## DLV (Dec 10, 2012)

Had to ad my personal experience: Temp gauge at 11 o'clock, temp gauge dies, pull the battery, temp gauge comes back, and dies a few miles later. Take out my el cheapo vag com reader ($40 at amazon) and get code P2181. I reset the code and my temp gauge comes back, goes away, and comes back again. When it works, it only goes to 11 o'clock, not straight up to noon (as it seems it should if everything is functioning). 

So, yeah long story short, I had the thermostat and both sensors changed. Now my gauge is at noon and everything seems to be in order. 

FYI the dealer here in Manhattan quoted me $1k to do it, so I took it to a shop in Queens and they did it for $400. And it took them more than three hours to do (and said it was pretty much a pain in the ass). Ultimate Auto Care 718.392.2757. Highly recommended. 

Also, I believe silver squirrel is correct in that the thermostat gets weak. Your engine probably will not overheat and in winter it will take longer to warm up (and your interior heat will take longer to heat up). Many of your A3s can probably live with the problem but I am taking my car out to Wyoming next week where it will stay. Temps get to -20 below zero (farenheit) and that is going to be an issue, plus the interior of the car would be stone cold. 

2006 A3 2.0


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## Ponto (Jan 11, 2012)

16vsilverstreak said:


> This needs to be in the A3 FAQ.


Agreed... it could use a good update.


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## rambag3 (May 17, 2006)

I am having the exact same problem, got a CEL and my temp gauge is intermittent. I live in Ny too so I'm going to try Ultimate Auto Care. Tyvm all.


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## TBomb (Sep 23, 2009)

rambag3 said:


> I am having the exact same problem, got a CEL and my temp gauge is intermittent. I live in Ny too so I'm going to try Ultimate Auto Care. Tyvm all.


Replace the thermostat and it will fix the problem. This has been proven to be the solution countless times. :thumbup:


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## rambag3 (May 17, 2006)

TBomb said:


> Replace the thermostat and it will fix the problem. This has been proven to be the solution countless times. :thumbup:


I'm waiting for DBC Tuning to ship my cam follower and DV so I can just have the shop do the install on them and fix the temp gauge at the same time. When it will ship I have no idea.


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## rambag3 (May 17, 2006)

DLV said:


> FYI the dealer here in Manhattan quoted me $1k to do it, so I took it to a shop in Queens and they did it for $400. And it took them more than three hours to do (and said it was pretty much a pain in the ass). Ultimate Auto Care 718.392.2757. Highly recommended.
> 
> 2006 A3 2.0


Went to the above shop, changed the thermo, CEL gone, thermo at noon. But what I will say is, they did not want to do the cam follower or DV. I have banjo bolts so I thought they would do it for me.


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## hansumstranger (Jan 10, 2013)

*What are B3800, B2800 & B2000 codes?*

Just picked up a 2006 A3 and I love the car. But, I'm having the same 'efin issue as most of you guys have/had. 2nd day Battery died, found out it was the original battery, so I put in a new one. 
Next day, temp gauge dies and CEL lights up. 
My OBD scanner popped up P2181, which I see is for the Performance Malfunction in Cooling System. 

I rescanned and B3800, B2800 & B2000 showed up. 
Can anyone help tell me what these fault codes are? 

This is my first Audi.. i'd hate for it to be my last 

Thanks!


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## 16vsilverstreak (Dec 5, 2001)

I've owned many VAG automobiles, I've been driving one for the past 18 years. In my opinion Audi went cheap on the early A3s. I owned a 06 2.0t six speed. The T-stat job will take about four hours if you have the correct tools. A problem that I had with mine that was causing a lean condition at idle was a cracked vacuum hose from the brake booster to the manifold. (I still have a NOS hose). It was cracked at the manifold side. The 2.0t A3s are blast to drive but they do like to be wrenched on. Make sure you are checking your oil at fill ups because they do consume oil. You do not need to change any temp sensors for the dead temp gauge, it is all due to the t-stat. I traded mine for a 06 V8 Touareg.


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## UberMike (Dec 9, 2003)

My temp gauge died on the way to work this morning. Just wondering if it is safe to continue driving for the next couple of days while I get it scheduled for the repair?

Will replace the Thermostat and possible the coolant sensor.


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## Travis Grundke (May 26, 1999)

UberMike said:


> My temp gauge died on the way to work this morning. Just wondering if it is safe to continue driving for the next couple of days while I get it scheduled for the repair?
> 
> Will replace the Thermostat and possible the coolant sensor.


Yes, it's safe to continue driving. I went almost a year before replacing mine.


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## 16vsilverstreak (Dec 5, 2001)

Yes, it's safe. Just double check your coolant level. You can reset the coolant performance DTC and the gauge will come back every time.


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## UberMike (Dec 9, 2003)

So we had relatively mild temperatures over the weekend. The gauge came back and the CEL cleared itself. Coolant level is spot on. 

I'm going to hold off on replacing the temp gauge and sensors as I will likely need to do the timing kit in the spring. 

Thanks everyone for your help!


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## dreaminga3 (Jan 20, 2009)

UberMike said:


> So we had relatively mild temperatures over the weekend. The gauge came back and the CEL cleared itself. Coolant level is spot on.
> 
> I'm going to hold off on replacing the temp gauge and sensors as I will likely need to do the timing kit in the spring.
> 
> Thanks everyone for your help!


There is one foolproof diagnostic for knowing if it's a sensor or the thermostat. IF IT'S A 2006, AND IF YOU CLEAR THE CODE AND THE GAUGE STARTS WORKING, IT'S THE THERMOSTAT. Not sure about post-2006.
I've been through this whole routine. Good luck with it!


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## vwlippy (Jul 17, 2001)

Happened to me. Temp gauge would work one day and not the next. Finally had the thermostat replaced and never had the prob again.


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## Dr Chill (Aug 24, 2011)

08 A3 2.0T. Temp gauge stopped working. Vag readout shows coolant temp to be 0.0 despite engine being warm. No warmup or cooling issues. No CEL but following code:

P2181 Performance Malfunction in Cooling System 

Tstat or Temp sensor?


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## yonip79 (Feb 16, 2011)

Dr Chill said:


> 08 A3 2.0T. Temp gauge stopped working. Vag readout shows coolant temp to be 0.0 despite engine being warm. No warmup or cooling issues. No CEL but following code:
> 
> P2181 Performance Malfunction in Cooling System
> 
> Tstat or Temp sensor?


 change your thermostat that's the problem.


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## Dr Chill (Aug 24, 2011)

Cleared DTC's and gauge works again. If it occurs again, I'll swap out the thermostat.


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## Twistedchild420 (Jan 31, 2013)

Going through the EXACT same thing atm.....guess i'll be buying a T-stat


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## mike3141 (Feb 16, 1999)

I'm surprised that a 2008 model is showing a problem. Most all of the reports of failed thermostats were from 2006's....


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## 2006_A3_2.0T (Jan 11, 2013)

My temp gauge dieded.

At first it was random and a battery disconnect would fix it. But now its dead.

I will order a t-stat.

Any DIY for my mechanic? I like to give him instructions of clearly detailed steps.


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## 16vsilverstreak (Dec 5, 2001)

The T stat on my A3 was one of the most difficult to swap. I've been wrenching on VAG stuff for over 15 years. Make sure your mechanic has a wide range of star bits. There is a very small one retaining a hose. The alternator has to come out. A set of water pipe clamp pliers will make the job much easier. If your guy is good a three hour job, if he has trouble it could be a six hour job. Happy wrenching.


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## 2006_A3_2.0T (Jan 11, 2013)

I highly suspected that. What else is needed? Gaskets? Part no.? I would save the coolant because its fairly new, if thats not a con.



16vsilverstreak said:


> The T stat on my A3 was one of the most difficult to swap. I've been wrenching on VAG stuff for over 15 years. Make sure your mechanic has a wide range of star bits. There is a very small one retaining a hose. The alternator has to come out. A set of water pipe clamp pliers will make the job much easier. If your guy is good a three hour job, if he has trouble it could be a six hour job. Happy wrenching.


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## earlcahill (May 9, 2014)

*'06 A3 overheating??*

Hello, 
This thread is intetesting and seems related to my problem, however my thermostat seems to be working fine.
My issue is my fan comes on now every time I turn the car off (for 2-4 minutes). My temp gauge rises to 90 as normal, but then the other day it went all the way to the red and the temp light came on. I took it in and was told it wasnt actually overheating, that it was a sensor problem. Yesterday they changed the coolant sensor but the same thing happened shortly after driving away last night. Now they think it must be the thermostat. They say the coolant seems fine and seems to be making it around ok-thus still not actually overheating. Can you offer any advice before letting them do the four hour Tstat change? You think that will solve problem??
Thanks a lot-


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## mike3141 (Feb 16, 1999)

Did they change both sensors? (apparently there are 2 engine coolant sensors--see post earlier in the thread)


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## earlcahill (May 9, 2014)

Only the coolant temp sensor was changed. Do you know if the other sensor is located close by? Would it have made sense to change both?

Thanks


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## SilverSquirrel (Jul 24, 2006)

did it overheating during cruising speed, or were you stuck in traffic/parked/idling?

year/engine type?

fault codes?

your location? Alaska? Texas? A hot day? A cold Day (in Hell)? 

Have you "fixed" anything on the coolant system lately?


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## earlcahill (May 9, 2014)

It's a 2006 A3 2.0T
I'm in kingston, canada, southeast Ontario, not particularly cold anymore. 
I did have a routine oil change about a week ago. Day or two after that the fan began coming on everytime I turned the car off. It had done that a few times in the past, usually on really hot days. During routine trips the last few days (appx 10 minutes to and from work) nothing seemed unusual except the fan coming on. Then during a longer trip (20/30 min, city driving) the gauge quickly went from 90 all the way to the red and then the light came on.
In general the car has been running well a I haven't done anything to it or the coolant system at all.

My receipt yesterday didn't give me any codes, just said the "coolant sensor was giving improper readings"
...I assume that doesn't help too much.

The mechanic was convinced that the car was not actually heating up. I'm not really so sure, and am nervous driving it may be trouble.

Thanks again-


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## SilverSquirrel (Jul 24, 2006)

There is an additional temp sender in the radiator, down low, near the outlet. Not just the one on the head. So could be electrical. including wiring faults or bad connections along the way to either sender.

Water pump impeller could be failing. car is 06, thermostat possibly mfg. in 05 This is 2014. Happy 9th birthday to your old thermostat. Time to freshen up.

get vcds codes checked first. (after it happens again, if mechanic cleared them)

with vcds, you can monitor real time temp at radiator and at head, while you test drive...


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## earlcahill (May 9, 2014)

Thanks again for your thoughts. Unfortunately in going to be away for th next few weeks and will not be able to try and figure it all out until early June. Perhaps I'll be back in touch again then-


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## unoudid (Nov 20, 2012)

Does this happen to the 3.2 also? I've had my car in the shop twice now. They'll clear the codes and I believe replaced the sensors but my gauge keeps dying after the first use.


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## SilverSquirrel (Jul 24, 2006)

unoudid said:


> Does this happen to the 3.2 also? I've had my car in the shop twice now. They'll clear the codes and I believe replaced the sensors but my gauge keeps dying after the first use.


Yes


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## unoudid (Nov 20, 2012)

SilverSquirrel said:


> Yes


Stopped back in at the mechanic on my way to work today. They brought the computer system out and we cleared the code. The gauge sprung right back to life. Looks like they will be replacing the thermostat today. I'm hoping that solves all of the cooling issues.

The computer started throwing a code on the lower radiator fan about it drawing too many amps. I'm wondering if that's related at all to the thermostat issue? This is the first time that code was thrown. The temps were running around 84 degrees instead of the 90 degrees but that's about all we saw that was out of norm.


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