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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old May 22nd, 2009, 09:42   #1
ibanix
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Default AC recharge help

Hey folks,

My AC lost it's mojo - no more cold air - a few weeks ago. I'm assuming it just needs a recharge, so perhaps you folks can help with a few questions:

1) How do I confirm it needs a recharge and isn't the AC unit gone bad?

2) What's the DIY process for recharging the AC? What tools are needed?

3) What refrigerant does it take?

Thanks!
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Old May 22nd, 2009, 10:05   #2
BobnOH
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if it lost it's charge it may (probably) have a leak that needs fixed. Hook up a pressure gauge to check, sorry, not sure of that procedure
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Old May 22nd, 2009, 10:20   #3
ibanix
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The car is 6 years old, I'd figure by now the refrigerant is spent. No?
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Old May 22nd, 2009, 10:23   #4
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Search and you will find a DIY troubleshooting procedure for AC. I'm working on mine now as well because there is no function (no cooling)

I think the first course is to check the voltage or duty cycle at G65 sensor. It should be 20% to 25% with a full charge and the exact report will depend on the outside temperature.

My refrigerant had leaked out last year and I had it recharged 11mo ago but I just checked G65 and it is 22.3% duty cycle so charge does not seem to be my problem. There are other things you (and I) can check such as does your clutch engage when you start the AC. Do your radiator fans turn on when you engage it (mine do).
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Old May 22nd, 2009, 10:52   #5
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http://forums.tdiclub.com/showthread.php?t=242699 post #1 links at the bottom has some troubleshooting help. It may save you several hundred dollars (over Easter Egg hunting with expensive parts) if you use it.

One warning when checking fan control module output voltage to the compressor clutch, check it loaded - stick safety pins through the wires with everything hooked up to check the voltage. Checking it unloaded, as is presently in the guide, can lead you astray. I should have the guide updated in the next week or so.

PM me if you need to.

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Old May 22nd, 2009, 12:00   #6
LiLredTDI
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hey Ibanix, AC systems are sealed systems, and refridgeriant NEVER goes bad or runs out except in the case of a leak. If it is a small leak you may go quite a while on just a re-charge however it may leak out immediately. I am not sure about VW's but most cars if the AC charge is low, the compressor clutch will not engage. Even if you do just re-charge and do not fix the leak, you may have to find this safety relay and jump it out to engage the clutch so the compressor will suck in refridgeriant.

There are fittings on the condensor line and the evaperator lines under the hood between the compressor and the heater core. The largest tube coming off the compressor is the suction line, and the smaller is the liquid line. The fittings will look similar to the ones you have on your tire. Here is where you must place the gauges to see how much pressure (if any) is in your system. You can do this with the car off.

If you have the dough, try to find a shop that specializes in AC repairs on autos and bring it to them. They have special dyes to trace leaks if there is one as it is sometimes nearly impossibile to find leaks if they are very small. You could also trace out the entire path of the AC system and see if a fitting is unusually oily, that could be an indication as refridgeriant contains oil.

good luck.
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Old May 23rd, 2009, 06:29   #7
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First, make sure your radiator fans come on when you push the a/c button.
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Old May 25th, 2009, 14:30   #8
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Ibanix,

All cars have a low pressure cutout. Since the oil is mixed with the refrigerant, when the pressure is low, it kills the power to the compressor clutch to keep it alive. Check at your compressor wire to see if you have power. I like a digital multi meter, but a test light would give you an idea. If no power there, use the DMM to check for continuity across the low pressure switch. It should be a 2 wire sensor screwed into the line somewhere or at the dryer. I'd look, but I'm actually on a road trip in the Jetta with the misses driving.

Here's a chart to check the static charge state of your car if you have gauges: R134a chart I'd check it when the car is cool so you know that the system isn't heatsoaked. All this will tell you is if you HAVE refrigerant in the system. It won't tell you if you have the correct amount. The compressor should be energized if you have above 40psi or so. That's a ballpark guestimate.

If you do need a recharge, you can possibly get it close by charging the low side line (the fat one), but I'd recommend having it professionally repaired by an A/C specialty shop. Plenty of garages will "fix" it, but I train these people day in and day out, and the expertise level varies dramatically. If you were in my area, I could steer you to somebody.

Do yourself a favor, though. If you do decide to do this yourself, watch your high side pressures and don't overcharge it. I would prefer to see one undercharged. More is NOT better. Also, don't use anything with an oil charge or sealant. If it was a slow leak and the gas escaped over time, the factory oil charge should still be there. Modern systems have charge figures to the hundredth of a pound. Surplus oil will take place of that wonderful, cooling freon, and benefits nothing.

This is one area, like alignment, that you can get it close, but it's almost impossible to get perfect without proper equipment.
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Old May 25th, 2009, 17:40   #9
DanG144
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Quote:
Originally Posted by Gearhead51
Ibanix,

All cars have a low pressure cutout. Since the oil is mixed with the refrigerant, when the pressure is low, it kills the power to the compressor clutch to keep it alive. Check at your compressor wire to see if you have power. I like a digital multi meter, but a test light would give you an idea. If no power there, use the DMM to check for continuity across the low pressure switch. It should be a 2 wire sensor screwed into the line somewhere or at the dryer. I'd look, but I'm actually on a road trip in the Jetta with the misses driving.

Here's a chart to check the static charge state of your car if you have gauges: R134a chart I'd check it when the car is cool so you know that the system isn't heatsoaked. All this will tell you is if you HAVE refrigerant in the system. It won't tell you if you have the correct amount. The compressor should be energized if you have above 40psi or so. That's a ballpark guestimate.

If you do need a recharge, you can possibly get it close by charging the low side line (the fat one), but I'd recommend having it professionally repaired by an A/C specialty shop. Plenty of garages will "fix" it, but I train these people day in and day out, and the expertise level varies dramatically. If you were in my area, I could steer you to somebody.

Do yourself a favor, though. If you do decide to do this yourself, watch your high side pressures and don't overcharge it. I would prefer to see one undercharged. More is NOT better. Also, don't use anything with an oil charge or sealant. If it was a slow leak and the gas escaped over time, the factory oil charge should still be there. Modern systems have charge figures to the hundredth of a pound. Surplus oil will take place of that wonderful, cooling freon, and benefits nothing.

This is one area, like alignment, that you can get it close, but it's almost impossible to get perfect without proper equipment.
Gearhead, after May of 1999 the A4's have used duty cycle (or pulse width modulated if you prefer) transmitters - not simple switches. The PWM transmitters are mounted on the high side. The signal it sends is used by the Fan Control Module to develop both high and low pressure interlocks. The signal is also used by the ECM - to figure AC load, I guess.

Everything else you said seems right on the money.

There is a chart in the links referenced in post #5 below that shows the approximate setpoints.

If you have time, I would greatly appreciate your review of the troubleshooting guide that I have tried to write. I have a new revision out for review right now.

I will add another link (tonight)to the thread referred to in post #5 for Revision 6 of the guide.
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Old May 25th, 2009, 21:21   #10
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Dan,

I noticed my error a little while after I posted. I was bouncing down HWY78 outside Birmingham, and I read some of your troubleshooting guide, but not all. I will try to give it a look soon. I didn't realize that VW was that advanced in '99. I assumed (wrongly) that it had an oldschool pressure switch. This VW seems to have a pretty in-depth system. Thanks for correcting me.

I think that diagnosing the electrical components should be easily done at home, but the actual charging of the system should be done by a professional.
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Old May 26th, 2009, 03:23   #11
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Gearhead,
When you have time, please review rev 6.

Please wait until you are not driving.

Will you make it to Asheville June 5,6?

Dan
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Old May 26th, 2009, 03:49   #12
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Is there any difference if I used R-134A from Harbor Freight (in Buffalo) which is $10 last I saw (for just the fill, not the hoses) or Red-Tek at Canadian Tire for $15(6-oz cans, not the hoses with are $50 with the can, but it's not a drive to Buffalo), how interchangeable is this stuff?
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Old May 26th, 2009, 04:57   #13
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DanG144,

I might go. I want to, but I also need to run to Florida and pick up a new demo trailer. It's a wants vs. needs thing.

BTW, I'm no guru on these things. I haven't spun wrenches in years, and I train technicians on proper RRR machine usage and answer technical questions about machines.

je,

I would stick to 134a. That's what the system is designed for and it's has known performance characteristics.

Unfortunately, there is even a possibility that you're not getting 134a unless you buy from a reputable vendor. I've heard horror stories of people getting shipments from overseas, and there's something else in the containers. The sale of identifiers is going back up, oddly enough. We had these problems during the shift from R12 to R134a.
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