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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 July 27th, 2012, 15:08   #1
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Join Date: Aug 2000
Location: NC USA
TDI(s): 01 Jetta
Default 01 Jetta A/C and radiator fans not working

Original issue,

A/C not cold, Car has 370,000 + miles, changed A/C compressor, expansion valve and receiver dryer. Recharged with auto parts Freon that included oil, I’m pretty sure I over charged it so I removed some of the charge a little at a time. Bought a set of gages, was reading high pressure on low side, low pressure on high side. Still never blew cold, just cool… 50 degrees or so.

Was advised I may have a blockage on the high side between the compressor and the test port so I purged the system by disconnecting at the expansion valve (firewall) and the high pressure side of the compressor. Back flushed it with shop air, isopropyl alcohol and purged with dry shop air for 30 minutes, closed system and added 4 oz of A/C oil, one can of R134 to the high side, started the car and selected A/C and interior fan on high. The Compressor clutch never engaged, and here is where I really messed up.

Beside the high pressure port there is a pressure switch, at least that’s what I thought it was. I decided it must need to see a pressure there to allow the compressor to engage so I disconnected it (3 pin plug) and jumped the 2 outboard pins. The jumper wire got hot and my son saw smoke from somewhere… so I removed the jumper and shut down.

Now with the ignition on, A/C selected on, and the interior fan on I do not have the 2 cooling fans behind the radiator running. Following DanG144’s troubleshooting guide on Pg 2 http://forums.tdiclub.com/showthread.php?t=209698&highlight=test+fan+control +module&page=2
it lead me to the FCM. I replaced it (mail order) and it did not fix my problem. When the ignition is on, A/C selected, interior fan on, I get no cooling fans (radiator). I also have a friend with a A4 Jetta that agreed to let me swap his FCU for testing purposes with no luck (The new one is not dead on arrival and works in his car)

The radiator fans are good, I direct connected them both in low and high with jumpers from the battery. The A/C clutch is also good, engages direct connected. Fuses above the battery are good,

I’m stumped, any ideas? DanG144 says FCU or wiring harness.. I’ve eliminated the FCU, how do I troubleshoot the wiring harness?
'01 Jetta TDI, Silver Arrow, GLS, Black Leather, 5 speed, E Codes, Euro Switch, Upsoluted at birth. 5 timing belt changes, .658 5th gear swap, 446K miles as of spring 2015

2015 Jetta TDI SEL, 6 speed, awesome driver assistance package with THOSE headlights...
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Old April 25th, 2015, 15:59   #2
Join Date: May 2002
Location: Dallas, TX
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I have the exact same issue...replaced the fans and new FCU and still no fans come on in any combination.

What did you ever find to be the issue?

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Old April 25th, 2015, 16:11   #3
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Join Date: Oct 2014
Location: Windsor

run a circuit from you battery directly to the fans so if they kick on. you should also break out a wiring diagram and meter and check for continuity on all circuits related to the system. these harnesses tend to be brittle and you wouldn't even notice it when it's right tucked up at the connector.

be careful though if you're using that pdf manual that's floating around... none of the schematics in there match the wiring when I compared wire for wire. (atleast in relation to the fan wiring)

this is the schematic that I found by luck that matched. the google has saved my ass many a times lol.

Last edited by e84; April 25th, 2015 at 16:23.
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Old April 25th, 2015, 19:21   #4
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Location: DE

How low was the dew point on that " dry air" ?

You never mentioned pulling vacuum on the system ?

How did you charge from the high side ?
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Last edited by Dimitri16V; April 25th, 2015 at 19:24.
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