3rd AC compressor in 3 years

I've got to say I am pulling my hair out on this one. My AC compressor died in July of 2014 and it was replaced with a new one. That compressor's clutch failed to engage in April of 2016 so I bought another new compressor. Well now that compressor's clutch will no longer engage so I now I need to buy another! This is getting ridiculous! Is this common with the A4 ALH TDI's?

No, it is not common. How are you diagnosing these compressors?

The mechanic is the best in the region. I have seen people drive hundreds of miles to have him work on thier TDI. He is a very well respected mechanic on this board. I have total confidence in him. The compressors are valeo and again I have had many people talk up the quality of valeo. Just frustrated that i have to go through this again.

Doesn't answer my question... and I would only use a Sanden compressor on there (that is OEM), although an actual genuine Valeo should be perfectly fine, but I admit I have no experience using one on an ALH.

Since you do not know why the original compressor was replaced, and do not even know IF this one needs to be replaced, it is tough to comment on if this is indeed some strange pattern here or something totally different.

I know dead cooling fans, which ARE common, will overtax a compressor as well as the clutch.

I have had to replace two coils on my '03 Jetta and '03 Golf TDI's... bought them off of ebay. I first made sure that both of my fans were working (large and small). Large one wasn't working on either car. Bought two new large fans from European autoparts (or something like that... in Colorado) About $52ea/free shipping. Replaced those, pulled the coil plug off of the coil/clutch assembly while the compressor was still on the car, tested it and found no resistance. I think it should be around 3 to 4+ ohms... circuits were both open --> coil was toasted. Both went bad because of heat, I think. Both "popped" when pulling away from a stop light under normal non-spirited driving. Replaced the whole pulley/clutch face/coil assembly on both... about $85+/- for the whole assembly off of ebay. Both have worked fine ever since... fingers crossed.

oilhammer said:

Doesn't answer my question... and I would only use a Sanden compressor on there (that is OEM), although an actual genuine Valeo should be perfectly fine, but I admit I have no experience using one on an ALH.

Since you do not know why the original compressor was replaced, and do not even know IF this one needs to be replaced, it is tough to comment on if this is indeed some strange pattern here or something totally different.

I know dead cooling fans, which ARE common, will overtax a compressor as well as the clutch.

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Its showing the same symptoms from when the last compressor failed. You press the AC button in and the button then lights up but the compressor is not kicking on. I have owned this car since the day I drove it off the showroom floor so I can easily tell if the compressor is kicking on because the RPM's should drop a little and I should hear the click when the compressor kicks on.

That is not happening so I know the compressor is not kicking on. The last time that happened it was the clutch on the compressor that went bad. Now with that being said, what other problem could cause the compressor to not kick on besides a bad compressor clutch? Is there possibly a fuse that is blown? It was working fine when I pulled into the garage last night. When I went to drive it today the compressor will not engage.

InfoSec said:

I have had to replace two coils on my '03 Jetta and '03 Golf TDI's... bought them off of ebay. I first made sure that both of my fans were working (large and small). Large one wasn't working on either car. Bought two new large fans from European autoparts (or something like that... in Colorado) About $52ea/free shipping. Replaced those, pulled the coil plug off of the coil/clutch assembly while the compressor was still on the car, tested it and found no resistance. I think it should be around 3 to 4+ ohms... circuits were both open --> coil was toasted. Both went bad because of heat, I think. Both "popped" when pulling away from a stop light under normal non-spirited driving. Replaced the whole pulley/clutch face/coil assembly on both... about $85+/- for the whole assembly off of ebay. Both have worked fine ever since... fingers crossed.

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Can you please go into more detail here? I know about the 2 fans. What are the two coils? What is the whole pulley/clutch face/coil assembly?

RedTDIowner said:

Now with that being said, what other problem could cause the compressor to not kick on besides a bad compressor clutch?

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Pressure switch, bad wiring, lost AC charge.

You can replace just the clutch and pulley on these compressors. You don't even need to remove the compressor from the car to do it.

If you unplug the wire on the AC compressor and check for resistance across the 2 terminals (compressor side, not vehicle side) that will tell you if it's the clutch that's bad. You want to see resistance but just because you do see resistance doesn't mean the clutch is good. If it's an open circuit then it's definitely bad. If you remove the serp belt you can put 12v (I think, confirm this first) to the compressor and see if the clutch locks up by rotating the pulley.

I just bought a compressor from the junkyard. $40. All I wanted was the clutch assembly from the front. I removed that and transferred it to the compressor on my car. My compressor was not engaging when I pushed the ac button either. The fans would work but not the compressor. I didn't even have to open the system, no discharge and no need to recharge.

I've just changed two comp coils, one on my car and one on my sons.......took about an hour to do each one......not that bad.

RedTDIowner said:

Its showing the same symptoms from when the last compressor failed. You press the AC button in and the button then lights up but the compressor is not kicking on. I have owned this car since the day I drove it off the showroom floor so I can easily tell if the compressor is kicking on because the RPM's should drop a little and I should hear the click when the compressor kicks on.

That is not happening so I know the compressor is not kicking on. The last time that happened it was the clutch on the compressor that went bad. Now with that being said, what other problem could cause the compressor to not kick on besides a bad compressor clutch? Is there possibly a fuse that is blown? It was working fine when I pulled into the garage last night. When I went to drive it today the compressor will not engage.

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Ok, so all you (and now WE) know is that your A/C doesn't work, and you state the compressor clutch does not engage. This is your current problem. The cause is as of yet, unknown. You've made a HUGE assumption that it is the same cause. It may not be. You stated you have an individual who is very well versed in these cars, and has serviced your car in the past. Why not let this individual take a look at your car again? Let him diagnose the problem before you've jumped to any conclusions. Loss of charge, a bad HVAC control head, a bad FCM, a bad blower resistor, a wiring problem, a bad ambient temp switch, could all also cause the compressor to not engage.

To the Original Poster, as Oilhammer has stated, there are a multitude of things that can be responsible for the AC Compressor Clutch not "kicking-in" when you turn on the system, directly or indirectly.

All those items need to be tested before doing a total Compressor replacement. My experience with the Sanden Compressors has shown me they are quite robust internally. If there are no obvious leaks (oil) and there is still refrigerant in the system, there's really not much of a reason to suspect the problem is internal.

So, again....... rehashing Oilhammer's list !
-Fan Control Module (FCM) is known to be problematic
-Fans out front gone kaput causing other issues
-Fuse on top of battery (left Green 30amp fuse, the other two are for the ABS)
-In dash fan switch. Without the engine running, that switch should turn on the Fans out front in AC mode. If not, that switch is bad.
-The AC coil behind the Pulley on the AC Compressor can succumb to heat. The two wires are Positive and Negative. Applying 12 volts to them will create a magnet snapping the clutch face tight against the pulley housing. If not, the coil is bad.
-The clutch face, I suppose, can go bad. I've seen them that have been obviously very hot but still worked.
-Low refrigerant switch can malfunction (it is mechanical internally)
-Low on refrigerant
-Ambient air temp switch go kaput (Also, critters have been known to chew the wires on that sensor.)
-Wiring problems
-Blower resistor in the fan housing on the passenger side

oilhammer said:

You stated you have an individual who is very well versed in these cars, and has serviced your car in the past. Why not let this individual take a look at your car again? Let him diagnose the problem before you've jumped to any conclusions.

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Unfortunately my mechanic retired and the one I have an appt with tomorrow says they don't replace the pulley/clutch face/coil assembly if its the problem. They just replace the entire compressor. I wish I knew a VW mechanic close to Louisville KY that is willing to troubleshoot all these possible AC problems you all listed above.

Changing a compressor for a bad coil is dumb.

But, this is the third identical failure, so something else is going on. I suspect the root cause is electrical and if you don't find it you're going to keep buying compressors.

Genesis said:

Changing a compressor for a bad coil is dumb.

But, this is the third identical failure, so something else is going on. I suspect the root cause is electrical and if you don't find it you're going to keep buying compressors.

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I completely agree. I just can't find a mechanic within an hour or so of Louisville KY that is willing to trouble shoot all the things you all have listed above. They just want to replace the compressor and be done with it.

If you told the mechanic you had 3 compressors already and they just want to install another then they are parts changers, not mechanics.

Simple test.
Turn the key on (don't have to start)
Turn the AC on.
Both radiator fans should run.
If not possibly FCM.
The compressor also grounds in the same area as the fans.
Have you measured the voltage getting to the compressor? Should be 12 volts.
I use a T pin to poke into the wire, not unplugging it.

On mine both fan's ground somewhere on the front left, trace your fan wires, check the grounds, clean as needed.

OP,

Hypothetically, if the compressor is not "kicking in" it can be because of a slow leak causing a lack of charge.

Replacing the compressor will solve the issue - you will install the new compressor and recharge the system. The system will work fine until the slow leak once again causes the compressor to "not kick in".

However, all that would have been needed would be to repair the leak, and recharge the system.

As above, replacing a compressor due to a bad coil/clutch is silly.

Replacing a compressor due to a possible slow leak is even more silly.


Diagnose the car properly before throwing any more parts or speculation at it.

Maybe take it to an AC guy rather than a TDI guy who won't change a clutch if that's what's needed.

I'd trust an AC specialist over a TDI specialist in this situation.

Meh -- they're even worse (AC "specialists")

There's not one who will, for example, change the RCV in an ALH vehicle rather than changing the compressor -- even if the car has a good charge, no evidence of leakage and no abnormal noises.

It's a good bet roughly $100 worth of parts and an hour or two of labor will fix the system. Yet not one place out of a thousand will do that. They will ALL try to hit you up for well north of $1,000 to change out the compressor, condenser AND evaporator, which requires ripping the dash out of the car and is (easily) a full day's work.

I found the problem thanks to AndyBees telling me about the 3 fuses over the battery!



So I guess I need to replace the plastic fuse cover over the battery since part of the fuse is stuck down in there when it melted? What could have caused this?

See, you do not need a compressor after all! Proper diagnostics are always the way to go. Never jump from Step A to Step Q.

What "caused" it is most likely the same that causes that sort of thing a lot on these cars: they just are not quite up to the task and/or there was a bad connection in the fuse holder that was made worse by over time the plastic heating and contracting.

I like to R&R those fuses from time to time and look for any burn marks on the terminals, indicating a poor connection.

We replace a half dozen A4 fuse link boxes a year on average I'd say. Usually it is the main wire from the alternator that melts, but sometimes it is one of the fuses like yours.

No big deal, easy to replace. Dealers used to keep these on the shelf, the one closest to you may still do so. Otherwise, they can order you one or you can find one online and have it shipped to you.

Thanks oilhammer. Should I do some more research to try and find out why the fuse blew and melted like that? Or would you just replace the fuse cover over the battery and not worry about finding out why it happened?

Like I said, it happens on these cars. You likely had a bad connection and eventually it just caused enough heat to melt and distort the plastic enough that the fuse burnt/lost contact.

I would replace all three fuses along with the box.

I assume this is exactly what I need?

https://www.amazon.com/BaiFM-OEM-Fu...0916&sr=8-4-fkmr3&keywords=A4+fuse+link+boxes

The local VW shop wants $135 just for the part. I imagine the dealer wants even more.

Make sure you disconnect the battery (negative side first) before removing the fuse panel.

Hopefully, this is the only problem. I'm thinking the high/low pressure switch would have protected the system if pressure got too high while sitting at a traffic light, etc., with the AC On. .......... would been honored to meet you but I'm glad you never had to make the almost 4 hour drive!

You could use something like this "in-line" spade fuse holder as a temporary fix... available at your local FLAPS (Friendly Local Auto Parts Store)... Of course, you'd have to cut the one wire on the connector side or scrape the plastic off for splicing purposes... your call!

Picked up the part at a junk yard for $6.55. After I installed it both fans behind the radiator kicked on and the AC started working. Thanks for all the help fellas. I have book marked this thread for future reference.

Nice work. That junk yard part is a good buy, I'm not sure what that Amazon part was.

"Spade" style connectors, especially where they can get exposed to environmental temperature shifts and moisture, along with being relatively high-amperage, are trouble. Once they lose a bit of tension resistance goes up and that causes them to get hot.

The heat makes the tension relax even more, which of course makes the resistance go up more and thus it gets even hotter! Eventually it starts arcing and burns up (just like it did.)

The best you can do is keep these sorts of connections clean and, if you find evidence of them getting hot, replace the components involved before they fail -- because fail they will, and soon.

Very common failure point. I have replaced that box on my own car more than once already.

My car is currently waiting for a new fan to come in. I noticed my ac was so so when I was driving but cold when I was sitting at lights on the way home from work. Did the fan test and found that the large fan was not working. It did start running after manually turning it, but it had a grinding feeling inside.

Even though I got the used part for $6 I went ahead and bought the new part on Amazon for $14. I figured I might as well keep one on hand since they are so inexpensive to buy online and its a common problem. I did the same thing with the old brake switch and wouldn't you know since I have had the extra one on hand it hasn't gone out for almost 10 years.