Sounds like it might be the high/low pressure switch. They fail all the time and cause exactly what you are describing.
- Peter
I have a 2001 Jetta VR6 with 19K miles. My AC seems to fading in and
> out. It will be really cold when I start out, then I start driving and
> it just goes-still blowing but not it's hot and humid, not cold. It
> just went from really cold to blowing warm for up to 10 minutes tonight.
> Then it just kicked in and went freezing cold. I did not screw with the
> knobs--it just came out cold all of a sudden. I've checked for plastic
> bags stuck under the dash, but can't find anything. Also, I'm in Florida
> and it's about 85 and humid. You can really feel it when the cold air
> cuts out--it gets very uncomfortable fast. Anyone have any ideas? Even
> if I take it in--if it's working at the time, how will they be able to
> tell why it is cutting out intermittently?
>
Basically sounds like the gremlin that exists in my 95 GTI VR6. Couple of questions:
When the car is warm and you are stoppped just idling does the A/C work or does it kick off and on like its trying to work?
When it went off did it seem to stay off or do you hear the compressor click on and off multiple times when you are driving. Since your car is only a few years old the compressor is still pretty quiet but you should hear an audible click. Turn the A/C on and open the windows to hear it.
Does your high speed fan work when the A/C is on or off.
There are alot of things that can cause the A/C to kick off:
Not enough freon in the system or too much
Bad compressor - don't think it applies in your case
Bad A/C Thermal Cut off switch
Bad relay
Something else that I'm not aware of, like a bad ground, wiring
Since your problem is soooo similar to what is going on with my car, I'm pretty sure its a bad pressure switch which is located on the lower front right of the car and is attached to the receiver/drier which looks like a small metal cylinder the size of a oversized Coke can. The switch is attached to the "can" and can be unscrewed and replaced without emptying the A/C system. I have yet to receive and install the switch so I don't know if my problem will go away but I'd bet money it will. I've traced the electrical system using the diagrams and I'm also replacing the A/C cutoff switch which is only 12.00 and is directly tied to the operation of the A/C and is connected to the pressure switch and really can't be tested without a scan tool. On your car you may have a relay that located under the dash which may or may not be bad. The later VR6's have them, my car doesn't. If you hear clicking under the dash when the A/C goes off the relay may be bad.
I'd bet money that its a bad pressure switch/ AC Cutoff switch or maybe a leak in your system that is causing the pressure switch to go off and shut the compressor off. If you possess any mechanical skills, you can do the diagnosis yourself by purchasing a low pressure gauge from Pepboys - Autozone or even Walmart and hook it up to the low pressure connector thats located at the firewall on the right of the engine bay and check the reading when the A/C is running. If your charge is good, you can replace the pressure switch and take it from there. Since the switch is only 39.00 from Impex or GermanAutoParts.com. A/C gremlins can be hard to located unless you have the right equipment like a VAG scanner or high/low pressure gauges so a trip to the "dealer" or A/C specialist may be in order. Its not uncommon for the pressure or A/C Cutoff switch to go bad as they are exposed to pressure and extreme heat - over time they either corrode or get heat damage. If you want to save some time and aggrevation take it to a specialist but expect to pay big dollars tracing the problem and getting it fixed.
The problem is it only goes out when I've been on the Interstate for about 10 minutes late in the day when it is hot out, and the engine is also hot. Last night coming home from work, it went out after about 10 minutes running at 75 mph, after working ok all day, and did not come back on. When I brought it in today--it of course worked fine and they just let it run inside (where it is nice and cool) and could not get it to go out. After 4 hours, they still didn't know. They said there was no way to know if it is the pressure switch until it acts up (obviously they won't just replace it). So they gave me a loaner and said on Monday, there would be someone to take it out on the Interstate to try to replicate it. It is obviously something having to do with the heat and/or engine running at high speed. Nothing came up on their computer.
The other thing bugging me about this is that the car only has 19K miles, but is 3 weeks out of warranty. So although I have Masterguard, I've still got that $100 deductible to pay. This is the fourth time in two months it's been to the dealer for repairs (2 bad brake switches and the window fell into the door. I was going to buy this car at the end of the lease because I love the way it drives, but I'm starting to wonder about all those quality problems I've heard about, but thought I'd escaped.
Ok, well the switch may be defective but since it appears that its engine/heat related you may want to look at a few things. In my last post I asked a question about hearing clicking noises. When the AC isn't functioning roll down your windows and listen for a brief click repeatedly. If you hear it let me know. This is the sound of the compressor trying to work - its the sound of the clutch engaging. If you hear click - pause (time) click the compressor is attempting to engage but can't because the pressure switch is cutting it out. In this case your Freon is way low or the switch is shot. To have the dealer replace the switch you need to tell them this - its pretty much the only way to diagnose the problem effectively. In my experience mechanics are good at diagnosing problem but the dealership puts a time limit on what they can and cannot do. They won't take you car out for a 1/2 hour and try to figure everything out on a test ride if they can't find anything on the computer. Its not cost effective to the dealership - they do have other work and if you want the problem fixed your going to have to rule out all the possibilities. My dad has a newist Jaguar XJ8 and he had an AC problem that over the past year has cost Jaguar about 3500 in repairs. It wasn't because the dealership was incompetent it was because some AC problems are hard to diagnosis and some systems are pretty complicated. In our system its very basic. The system will only work if the freons pressure is correct or there isn't a heat related problem to cause a switch to turn off the system. In the VR6's case there are only three or four electrical switches that can turn it off. One is the pressure switch, two is the AC Thermal Cut off, three is the ambient air (outside temp sensor) and four is either a bad fuse or relay.
There is an AC Cut Off Switch which is located at the front of the engine and it controls the high speed setting of the fan and the A/C. It is attached to the coolant pipe and is the brown sensor/switch at the right of the three switch port. It basically reacts based on the temp of the coolant and will switch the AC compressor on and off based on set values. It should have four wires and will also control the third speed of the front blower fan. Once the A/C stops working, let the car cool down for about an hour and try it again. If it work for a while then cuts out and won't come back while running at the same speed (approx) then its most likely the switch. Generally if the A/C pressure switch is going or shot the A/C clutch will kick in and out repeatedly (or not all) if its defective. Depending on the pressure of the Freon the AC compressor may work at idle but drop out when above a certain RPM, not work at all or repeatedly turn on and off when above idle or at idle. Its a pressure thing. When the RPMS increase the pressure in the system may increase or decrease and depending on the range value of the switch the compressor will turn on or off. If the switch is shot or defecting those ranges will be either very large, very narrow or may top out at an incorrect value (the piston in the switch is basically stuck and can't realize its full range of motion).
When yours cut out were you going at a constant rate of 75 miles and the A/C worked ok for awhile then shut off or did it happen as you hit 75 mph (if this is the case - does the system resume when you drop your speed) or does the system return to working after the car is cooled off or cooling off. Know I am asking a lot of questions but there are many variables to consider.
If its heat related replace the cut out switch its about 15 dollars from the dealer - its pretty easy do replace, and is located in a place you can work without jacking up the car. The dealer will charge you a lot to replace it and probably will want to drain your cooling system in the process which ISN'T necessary. But since you still are under some sort of warranty why not - the jobs going to cost you more than 100 at a dealership anyway. When you were at the dealership did they do an AC Compression Test and Freon level test? They should have.
Its most likely one or the two and the cost to fix if you can't do it yourself should be pretty reasonable. If they can't figure out what the problem make them replace both switches. Unless your compressor is failing (unlikely) or your Freon level are low they are the only obvious things that are basically making the system work or not work in your case. The only last thing to consider is some short in the electrical system. This most likely isn't the cause since you can nearly replicate the problem and should really only be considered once the two switches are ruled out.
Sorry to be so long winded but I've just gone through a pretty extensive diag on my car which was experiencing simlar symptoms.
"Suzanne" wrote in message news: snipped-for-privacy@rr.com...
It's very difficult to hear anything with the windows open, but I'll try going very slow in a quiet neighborhood.
They checked the Freon today and said it was a little low, but that was not causing the problem.
It has happened a few times two days in a row (three times Thursday and again on Friday) First time, it was morning (cooler) and I drove 12 miles on highway--just after I got off, it started blowing warm air and then corrected. That afternoon (very hot and car sitting in heat all day) I drove 10 miles on interstate and after I got off it blew warm for a few minutes. I turned the car off and back on and it blew cold. Same day, about one hour later, I got on the interstate and after about 2 minutes, it blew hot. After I got off the highway, about 2 minutes later (and doing about 55) it suddenly corrected and blew out cold. Next day--I drove to work (12 interstate miles and then 15 minutes in regular traffice)--it was fine. Went out at lunch and it was fine. After work it was fine through regular traffic (I thought it was fixed). Got on the interstate and after about 7 miles at 75, it suddenly went off (not the blower, just the cold air). It's extremely humid here and you feel it immediately. It then stayed off for the rest of the way home (about 15 minutes). So I would say the problem is getting progressively worse. This morning it was fine on the way to the dealer (and apparently after they let the car run for a couple of hours). I'm beginning to think that if they do not find it, I'll take it and the minute it cuts off, drive straight to the dealer, even if it's 5:30 at night. Meanwhile, they gave me a real cute brand new Beetle to drive--it's no VR6, but kind of fun for a loaner.
I don't know about the compression test, but they checked the freon.
Don't be sorry--I like to get as much information as possible--I'm a researcher. I don't really know to work on cars, so I have to have the dealer do it. Although, it's 3 weeks out of the bumper-to-bumper warranty, I've got VW Masterguard, which should cover it I would hope. I am also going to put in a call to VW and see if they will cover it considering everything. I do have a pretty good relationship with the service manager at VW (who wasn't there today), so he may help me out with VW. They can't really tell what there is to cover until they find the problem.
There is one other thing that may or may not be related. Ever since I've had the car, when I turn it off after driving in very hot weather and at high speeds, I occasionally hear a fan under the hood blowing really, really loud. The first time it scared me because I had gone into the house and when I came out the fan was going full blast -- it was so loud that I thought the car was still running after I turned it off and walked away. I mentioned it to the dealer and on a few forums, and everyone said it was normal, so I blew it off and ignored it. But it is extremely loud for a little fan--and it was on the first time the ac went out and I turned off the car.
From what you are describing its probably the pressure switch. A few minutes shouldn't cause the AC Cut Off switch to turn off the compressor unless it was really wacked. Since its getting progressively worse its most likely the pressure switch. If you are not hearing anything squealing (slipping sepentine belt) or grinding noise (bad compressor) its most likely the switch. Have them replace it!
If you want them to replace it, you need to take the time and have them test drive the car with you to show them the problem. Take it to them after you have driven the car for at least a half hour when the car is fully warmed. Schedule an appointment and make sure they have someone - even its the service manager to take the test drive. Don't leave the car with them again - you won't get satisfaction and you won't know if they actually drove the car for a reasonable amount of time. I've had problems with a new Mercedes - not A/C related but simlar ghost problems with the radio, etc and the only way to get them to do anything is to take the Service Manager for extended test rides with both of us in the car. If you can't seem to get satisfaction with your dealer you may want to contact VW Customer Relations. Detail the number of times you've been to the dealer and that you have received no satisfaction and would like the matter resolved. They generally will contact the dealer and shake them up a bit - just be nice to the rep and it will go a long way. Explain your situation and hopefully they should intervene.
The big problem is that it seems to be at its worse around 5 pm. Every time it's screwed up, it's been late in the day. Other than the fact that it's been sitting in the 90 degree heat all day, I have no idea why. I work full time (and go to school two nights a week) and it is really difficult to drive the 20 minutes over to the dealership when the AC goes out to try to show them. By the time I get there, it could be back on. I do believe someone drove the car around today and I have no idea why it didn't act up. Getting someone to get in my car at about quitting time doesn't seem real viable. I have two possibilities. They offered to give me a loaner and let their mechanic take it home for a day or two. I'm sure it will crap out on him after work, so I'm thinking this might be ok. The other is that the switch will get worse to the point of not functioning all the time. I hate to go to VW before the dealer has tried everything--they really seemed sympathetic, but said that VW won't honor the warranty unless they know for sure the part was bad. If it is the pressure switch, why would it not show up on their computer check? And do you think it will crap out entirely at some point? Should I just wait and sweat it out (literally)? Or should I find myself a really good little shop that works on German cars and might actually know what it is?
S Tim>If you want them to replace it, you need to take the time and have them test
I'd let them take it for a few days, but I don't see the problem. They have done all the checks including the pressure/Freon test so whats left - the pressure switch and the coolant switch (AC Cutoff) both parts are relatively cheap - the AC Pressure switch is 38 online and the AC Thermal CUT OFF is about 12 from the dealer. Each part takes only about 10 minutes to install so we are not talking major bucks here and I don't understand why they dont just replace them and submit it for warranty since everything else (Compressor, freon content, fans, etc) in the AC system checks out. If they can't figure it out you should definately contact VW and explain to them the number of times you've been to the dealership and every time you have not gotten satisfaction with their service. Although they have been accomodating a resolution wasn't achieved in any instance which is unacceptable. The condition of your AC probably won't get worse over time; the part has failed, but who knows it may change as it corrodes but then again, it may not. Since the condition appears to be heat related, the AC Thermal Cutoff is definately suspect but I wouldn't rule out the pressure switch. Call VW and have their rep help work out a resolution, you shouldn't have this aggrevation especially when you've paid for a warranty.
Does the light on the switch turn off I was having that problem, and what it turned out to be was the ignition switch was going, the AC problem turned into a lighting problem, then a radio problem, then etc... :)
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.