A/C Compressor not turning on

torahtom

Well-known member
Joined
Jun 24, 2007
Location
Elizabeth, CO
TDI
1996 Passat Sedan, 250K
I had the system vacuumed and recharged but the compressor was not working. Then I realized I was missing the A/C relay. So I called VW and they gave me a 106 relay. When I got it, I had to plug it in sideways so it would go in. I then found out it was the wrong relay for my 96 Passat TDI. So I called VW again and they sent me relay 147. I plugged that one in and it fits right side up, but there is still no action on the compressor. I checked the fuse on the fuse box- still good. I also unplugged the wires going into the air compressor and tested them with a test light and they have no power.

Any ideas what the problem could be? Is the 147 relay the correct relay? Is there another fuse or relay that I missed? Thanks.
 

greenskeeper

Top Post Dawg
Joined
Mar 10, 2003
Location
USA
TDI
1998 Jetta TDI
unplug the 2 wire coolant sensor on the upper radiator hose. This is the overheat cutout for the A/C, if it fails open your compressor won't come on.
 

50harleyrider

Top Post Dawg
Joined
Jun 16, 2007
Location
charleston,wv
TDI
2005 B5.5 TDI/geared BSM, BV43A turbo,stage 2 TDTUNING. 2005 5sp manual passat tdi stage 2 tdtuning,BSM delete. 2015 Passat TDI 6sp manual.
How did they fully recharge the system without the compressor engaging? Aint gonna happen.
First make sure the system is charged as much as possible with the pressure from the freon can and the compressor is functioning by disconnecting the wire to the compressor and jumper 12v to the compressor and see if the compressor clutch engages and the sytem begins cooling. Make sure your fan is on high when you do this test so'you'll get heat transfer over the evaporator. Once the compressor engages, it should suck in enough Freon at the low pressure port connection to automatically turn the LP switch on. Shake the can hard as your filling to help boil the freon out of and into the system. Once you've reached that point there should be enough freon in it to keep the low pressure switch on at which point it should run on it's own without the jumper.When all tests out OK there,start looking closer at your relays and switches.

Caution: Don't over fill it. When it starts cooling and not cycling, it's usually close to full. Just add enough freon so it won't cycle on and off and you should be good to go. I'm not sure where the low pressure switch is on these cars but your not gonna get any voltage to the compressor until it's tripped from charging. You really need gages to do all this correctly.
 
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torahtom

Well-known member
Joined
Jun 24, 2007
Location
Elizabeth, CO
TDI
1996 Passat Sedan, 250K
Pulling out the temp. Sensor did nothing. Still no power to compressor. Must be some other fuse blown somewhere
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
That sensor opens when it gets hot. You need to jump the connector. There's also a pressure switch 50 was referring to. Might be an ambient air temp sensor too.
 

greenskeeper

Top Post Dawg
Joined
Mar 10, 2003
Location
USA
TDI
1998 Jetta TDI
good catch KLXD, forgot to mention jumper the plug after disconnecting!
 

schultp

Veteran Member
Joined
Mar 11, 2008
Location
Michigan
TDI
2010 Jetta Sportwagen, 6sp manual
Place your can of r134a in a pan of warm water when you are charging. It helps vaporize the contents and increases efficiency of transfer from the can.
 

50harleyrider

Top Post Dawg
Joined
Jun 16, 2007
Location
charleston,wv
TDI
2005 B5.5 TDI/geared BSM, BV43A turbo,stage 2 TDTUNING. 2005 5sp manual passat tdi stage 2 tdtuning,BSM delete. 2015 Passat TDI 6sp manual.
Again, make sure there's enough freon in the system to engage the compressor first then go back and look at your switches,relays. I've been doing this for decades and that is the easiest path to follow for us shade tree guys.
 

torahtom

Well-known member
Joined
Jun 24, 2007
Location
Elizabeth, CO
TDI
1996 Passat Sedan, 250K
Power to the compressor

Before doing all the other maneuvers, it seems I would need to get power to the compressor as there is no current going into it. I had the system vacuumed and at least 1.5 cans was put in of R134. So if no power is coming to compressor, nothing is going to happen. I had all my relays stolen:mad: along with the fuses. The 30 amp fuse for the fan and a/c circuit is fine as the fans are working. the compressor is almost new. The first relay for the #1 position of my fuse box was a #106 and it was the wrong one. I got another one and it is a #147 and 106 has alot more pins than the 147. Does anyone have a picture of their fuse box for a 96 Passat TDI they could post. I am thinking I am missing a relay or have it in the wrong place. The part # of the 147 relay I have in there is 1H0 959 142. Zeb at auburn vw called VW with my vin # and the 147 is the correct one. I can not match it up with the old one as the vandals stole all my relays. :eek: The later 97 fuse box is totally different. So I need to see a 96.
 

soup nazi

Veteran Member
Joined
Nov 29, 2008
Location
Australia
TDI
A5 Golf 2.0 DSG, MkIII Tdi Manual
Torahatom
Probably your compressor is not turning on because there are protections built in to the system to protect it. I would NOT recommend sticking power to it just to make it turn on, you may do damage. It may have too gas, wrong amount of gas, faulty high/ low pressure switch, faulty coolant temp sensor or faulty wiring to the compressor or one of the above mentioned sensors or switches.

Best thing is to trace back from the compressor wiring and find out where the power stops.
 
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