# A/C Problems



## TheMajic86GTI (Aug 9, 2009)

Having trouble with my a/c in my 97 golf. Earlier this year had problems with the low side reading really high and was told to change the expansion valve which i did and the a/c worked great for 2 months. Now im having problems with it again. The a/c clutch only engages in the morning or after the car has been off for more than 2-3 hours. It will work but not really get cold for about 15 min then shuts off and not work for the rest off the day or untill the car is off for awhile. i tested the psi in the lines with the compressor off: low side 105 psi and high side 100psi and a friend said this sounds about right. He was saying to check the low and high side switches?? Does this have to do with the black box under the coolant bottle? Just need some help or advice on what to check next to get this fixed cuz when it comes to a/c stuff its expensive and i usually just rip them out :banghead:


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## cuppie (May 4, 2005)

(not trying to sound like a d!ck...)
I know that you think you provided a good amount of info there; but, for an A/C diagnosis, it's lacking. And, especially given that you're having insufficent cooling even when the system is actually working (read: compressor clutch is engaged), it sounds like a mechanical problem, rather than an electrical problem

Good information would be:
With the car in an 'it should work' state, need the following:
--engine off:
- ambient temperature
- static pressures (low and high sides, engine not running)
--engine running, A/C running:
- high and low pressures
- ambient temperature
- outlet (vent) temperature
- compressor behavior (stays engaged? cycles on/off constantly?)
And, repeat _all_ of the above information when it isn't working at all.

Can you check the pressure switches? Sure. And, they're easy to find. Hint: they're installed in the A/C pipe(s.) Not sure on a MkIII; but, most older VWs use a dual pressure switch (both switches in a single unit.)

Question:
when you replaced the expansion valve, was the system professionally evacuated & charged (read: took to a shop, A/C machine used), or was it driveway charged (read: can from store used, system never evacuated first)?


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## TheMajic86GTI (Aug 9, 2009)

cuppie said:


> (not trying to sound like a d!ck...) ill ignore this for now
> I know that you think you provided a good amount of info there; but, for an A/C diagnosis, it's lacking. And, especially given that you're having insufficent cooling even when the system is actually working (read: compressor clutch is engaged), it sounds like a mechanical problem, rather than an electrical problem
> 
> Good information would be:
> ...


 Driveway charged


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## cuppie (May 4, 2005)

And, that's quite likely the root cause of the problem.
An A/C system _must_ be evacuated (vacuumed down) before it's charged. It's not empty - it's full of air. And, with that, moisture, too.

Depending on the relative humidity at the time of repairs (the time the system was opened), and the age of the parts, the drier is now quite likely saturated (and, therefore, trashed.)
That's only $30 for a new Behr part.
Oh, and: looking for that also gave the answer to where the pressure switch is located: on the drier. $36 (and, required with a new drier - apparently, there have been changes.)
A/C parts for your car

My recommendation:
Get it recovered (please don't vent the system to atmosphere! Dangerous, and illegal.) Replace the drier & switch. Then, unless you or a friend have the equipment to evacuate the system, take it to a shop for a _proper_ evac & charge.


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## TheMajic86GTI (Aug 9, 2009)

Good info. So what happens when u have a leak or an Oring breaks? Isnt it the same as not getting vacuumed? Just trying to understand this.


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## cuppie (May 4, 2005)

Same thing.
If you're just 'topping off' a leaky system (that hasn't completely emptied itself yet), you *might* be able to get away with simply charging it (but, you really should fix that leak.)
Take it apart for repairs, though (even "just changing an o-ring"), and it needs to be evacuated before charging.


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## TheMajic86GTI (Aug 9, 2009)

Do you think maybe evacuating it out now might get it to work? I saw at my local harbor freight tools they have an a/c vac machine. Do you think this machine is sufficient to do the job? Reviews seem good. Id have to get one regardless of what i do(i like to have all my own tools you never know when you will need them and saves money). http://www.harborfreight.com/25-cfm-vacuum-pump-98076.html or this one http://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html ?? Then i would purchase the new drier..


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## TheMajic86GTI (Aug 9, 2009)

Got around to working on the a/c again. Expansion valve done late last year, just put in the new drier and evaced then charged the system. Everything seemed to work fine. The next day in the morning when i took the car out the A/C turned on and was working and cooling fine UNTIL i noticed after about 15-20 min it started to get warm. I Checked the compressor and it was not engaging. So i turned it off then went in to work. When i got out of work and started the car i noticed the A/C was working again and compressor was engaging. But once again after about 15-20 it stopped. What i noticed was that when the car got to running temp or anything over 180 degrees it would cut off the clutch. When the car cooled down under 180 it would start working again. Is there a simple fix to this or something i can test to find the problem?


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## chickenfriend (Jan 31, 2005)

Since the AC seems to work well initially, and then starts blowing warm, suggests to me the evaporator might be icing up.

I don't know what controls that car has, but if it has a low-pressure switch, that would cause the compressor to turn off when the evaporator ices up.

"When you let it sit for a while, and then it works fine for 10-15 minutes" complaint could be caused by giving the ice time to melt off the evaporator.

It would be great if you have visual access to the evaporator to see if it indeed is iced when the air goes warm.

You could be low on charge (most probability), or have a faulty expansion valve.. You did say you had an expansion valve (txv) and not an orifice tube system? 

If you have any type of cabin air filter before the evaporator, make sure it is clean. No or low airflow can cause icing on the evaporator.

Also check the compressor clutch gap to make sure it is within specs. Check drive belt for slippage.

If you have gauges, the pressures on the low and high sides should be equal if the system has been off for a while. When the engine is started with the A/C on, the high side should go up and the low side down. The actual pressures are going to depend on a few things, like ambient temperature and system design.


If the pressures on low and high side are nearly the same when the system is running, then I would suspect a compressor failure.

If both low and high are too high while running, one thing to suspect would be an overcharge. A high pressure switch would be shutting off the compressor when that condition occurs.


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## TheMajic86GTI (Aug 9, 2009)

Thanks Chicken i do have gauges and ill try and check all of this on friday.


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## chickenfriend (Jan 31, 2005)

If you had the TXV replaced, make sure the sensing bulb was secured to the evaporator outlet, and insulated with cork tape.


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## TheMajic86GTI (Aug 9, 2009)

Had some time to work on it today. I just changed the expansion valve again since it was under warranty and maybe it was faulty. Evacuated the system then charged it. Used one can on it and the compressor immediately turned on, gauges read 27-28 on low side and 150 high side. Outside temp was about 77-78 degrees. A/C was cooling nicely and everything seemed ok for about 10 min, then the compressor clicked 3 times really fast off/on/off then stayed off. I then looked at the coolant temp gauge it had just reached 180. Gauges at that point read 115 low side and 125 high side. I had my grill of to see the evaporator and no icing that i could notice. So its the same gremlin. Any other ideas?


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## chickenfriend (Jan 31, 2005)

TheMajic86GTI said:


> I had my grill of to see the evaporator and no icing that i could notice. So its the same gremlin. Any other ideas?


If you had your grill off, you were checking the condensor, not the evaporator.


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## corrado9184 (Oct 17, 2007)

okay not only does our cars have high and low pressure switches to kick the compressor off, it also has a coolant temp switch that kicks the compressor off when it thinks that the engine is over heating. If its a 2.0 engine, its that top two wire coolant sensor on the coolant flange coming off the head. you will have to replace the sensor but you should be able to jump the terminals to see if it will allow the compressor to kick back in.


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## TheMajic86GTI (Aug 9, 2009)

Sorry ur right evap is under the dash i realized that after i wrote it. I was thinking it was something obvious and had a brain fart.... in the past i have had water leaking in the passenger side air compartment, kinda pours out when i turn. I looked into that in the past but i dont have access to it. It requires taking out the dash.


No Need to go any further. Thanks Corrado for your suggestion it worked! I jumped the sensor and now the a/c stays on and working. I'll be ordering a new switch tomorrow. Also want to say thank you to cuppie & chickenfriend for all your help as well, it has brought me to a better understanding of my a/c system. Something ive always ignored in the past to learn how to fix.


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## ziddey (Apr 16, 2006)

It sounds like your evaporator drain is clogged up. You might be able to blow/vacuum it out from the underside of the car. Had the same thing happen to a car of mine and had to deal with some nasty mildew.


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