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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, 09:37   #76
wanders
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Fuel Economy: AVG 48 MPG Best- 53 MPG
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Thanks Dan,

Checked mine, and all is A-OK.
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Old May 22nd, 2009, 20:45   #77
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Update...I decided to try a cheapie fix and it looks like it worked....

I shot compressed air into the rear of the motor casing. Lots and lots of dust came out. I tried it and they both work 100%. I think a shot of 90 psi compressed air would be really good preventative maint for this.
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Old May 22nd, 2009, 21:10   #78
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Just check that they work each time you fuel up. The fixes we do are usually temporary.
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Old May 24th, 2009, 09:35   #79
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I just received my VCDS with HEX-USB+CAN. Not sure how to us it yet, but I hope it helps diagnose my A/C issue. After reading the manual, it looks like it can do a ton of stuff.
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Old May 24th, 2009, 09:49   #80
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If you have a CAN bus system, and a Climatronic, you might be able to figure out how to use the VCDS for troubleshooting.

If you have an older, manual system, I do not think it will be much help with the AC system.

Do not hesitate to ask if you have any questions.

Dan
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Old May 24th, 2009, 11:35   #81
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Of course now that I have the tool to troubleshoot the A/C, it works w/o any issues. No fault codes were found ether. I did notice one thing that seemed to be a bit high. The turbo boost pressure was reading about 37 psi (2580 mbar) @ 3100 rpm (I do have a stage-2 chip tuning installed, but I did not expect that much boost).

I will try again later.
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Old May 24th, 2009, 11:53   #82
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If that is a stock maf, then that is right at the maximum possible output signal it can produce.

If it is a sustained reading, then it is probably too high for a stage 2 tune.
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Old May 24th, 2009, 12:32   #83
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I finally received some faulty output. I was measuring Auto-HVAC, when the measuring blocks started to read error group not available. If you switch off the measuring block group and back onto it, it would start to get an output again. Is it the Climatronic controls that I am getting the reading from?

The Boost pressure is not a sustained reading. Should I consider replacing the stock maf with an aftermarket?
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Old May 24th, 2009, 14:07   #84
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If the high boost spike is only for a second when you first get into the throttle, then it drops back and controls at a lower number then you can stick with your OEM maf. Putting on a higher span MAF requires a recode of your ECU, and perhaps your diagnostic program as well.

I think you are communicating with the climatronic unit. Is your Climatronic a Hella? There is a front panel diagnostic for the Hella, that you can do without a VCDS.

I know very little about the Cimatronic, and using the VCDS on one, but I am interested in learning.

Dan
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Old May 25th, 2009, 09:37   #85
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The boost only spikes for a second or two.

The Climatronic is not a Hella. Im not sure what make it is. I'm going to give it another try today to see if I can get some more info out of it.
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Old May 25th, 2009, 18:34   #86
DanG144
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Default Rev 6 of A4 Air Conditioning troubleshooting guide

Rev 6 of the A4 May 99- MY 2005 Air Conditioning Troubleshooting guide is now located at the bottom of post #1 in this thread.

This new revision has you measure the voltage to the clutch under load.
It has a few new values in it for G65 DC voltages, to help those that cannot lay their hands on a duty cycle meter.
It has you check the G65 output earlier in the troubleshooting; this may allow you to skip the hassle of unplugging the Fan Control Module.

Critical review comments are always welcome.

Dan
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Old May 26th, 2009, 18:34   #87
dmorrell
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I did some additional trouble shooting and the only difference that I can find is the compressor load. The compressor load is much higher when the A/C is putting out cold air. It took about ten minutes before the A/C started putting out cold air. I am not sure why the compressor load would change if all the other variables stayed the same.

A/C not working – car at idle (900 RPM)
Compressor rotation: 1000 rotations per minute
Compressor Current: .82 Amps
Compressor Load: 3.5 Nm
Evaporator Temp 38 C
Left Outlet Blower Temperature: 27 C
Right Outlet Blower Temperature: 27 C
Compressor Shut-Off Code: 0
Radiator Fan Activation (actual): 25.6 %
Radiator Fan Activation (spec.): 30.4 %
Engine Speed (increase): ON


A/C working – car at idle
Compressor rotation: 1000 rotations per minute
Compressor Current: .82 Amps
Compressor Load: 10 Nm
Evaporator Temp 38 C
Left Outlet Blower Temperature: 11 C
Right Outlet Blower Temperature: 10 C
Compressor Shut-Off Code: 0
Radiator Fan Activation (actual): 29.6 %
Radiator Fan Activation (spec.): 35.4 %
Engine Speed (increase): ON
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Old May 27th, 2009, 03:29   #88
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I am not familiar with the Climatronic setup. I have no experience with it.

If it uses the same compressor (and I THINK it does) as the manual AC system, then there is a mechanical compressor control system built into the compressor, the unit is replaceable, keeping the same compressor.

Look for recent posts on the subject (within the last month), maybe a reply by jcrews or joetdi? Look in TDi101, and both A4 forums.

Dan

Last edited by DanG144; May 27th, 2009 at 03:32.
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Old May 27th, 2009, 04:23   #89
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You might look at the compressor and verify the clutch is actually engaged.

And it seems very odd to me that the evaporator temperature remained constant at 38 C. That is much too hot for an evaporator.

The compressor load is likely a value calculated on compressor differential pressure (or perhaps just discharge pressure.)

Does your Auto AC module in VCDS have an OUTPUT TEST block?

That could be very informative.
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Old May 27th, 2009, 13:08   #90
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Great info here. It's too bad I didn't have this last year when my A/C quit.

I did the quick test yesterday; car on (not running), A/C button on, low fan speed (and turned on recirculate -not sure if that makes a difference in the test) and neither of my fans moved. However... I don't know that I've got enough charge in the A/C system in the first place. Does that matter in this test?

Here's the story: Last year my A/C quit on a road trip in ~110F heat. I was sitting still with the engine running when the A/C got warmer and warmer and the air got humid in the car. I found some of my old info and apparently I only had ~20psi static pressure in the system. I tried charging it with a leak detector kit and it wouldn't draw in a charge. I got some bad advice to jumper the compressor to force it to draw a charge in. It worked, but in the process the overpressure blow-off valve opened on the compressor. In the Bentley manual it says that the overpressure valve will blow off excess pressure and then close to keep from losing all of the charge. So I'm not sure what my pressures are like now, but I can put the gauges back on if I have to. It sounds like I've got fans (and maybe other systems) to troubleshoot first though.
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