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njt1rider Samba Member
Joined: August 18, 2013 Posts: 62 Location: Louisville, KY
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Posted: Mon Jul 16, 2018 6:24 pm Post subject: A/C cut off relay |
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So I sold my tdi swapped 93 weekender. I never got around to diagnosing why the a/c didn't work. I lived in it for 3 years with no a/c . Talking to the new owner today I was trying to help him solve the issue. Open up the bentley and within 5 minutes I find that there is a clutch cutoff relay on the auto van that isn't present with a manual. It appears that the relay just needs to be removed and hardwire the clutch wires per the schematic. Doh! Feel pretty silly now but here's my question:
Why do the autos have an a/c cut off relay that gets a signal from the tcm and the manuals just don't have the relay?
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22639 Location: NYC/Upstate/ROW
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Posted: Tue Jul 17, 2018 6:14 am Post subject: Re: A/C cut off relay |
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You don't have a TCM in a manual and Germany was too busy cheating on emissions to develop an ECM output to do the same.
(sarcasm) but probably the reason why.
It is a bit weird to have the AC cutout by the TCM - all other makes Ive worked on have the ECM cutout _________________ .ssS! |
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Zeitgeist 13 Samba Member
Joined: March 05, 2009 Posts: 12115 Location: Port Manteau
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Posted: Tue Jul 17, 2018 7:46 am Post subject: Re: A/C cut off relay |
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That's a weird one. The T3 uses refrigerant pressure/temperature switch(es) for the clutch cutout function and only ties the A/C system to engine management via the idle control relay...and perhaps the TPS under WOT conditions. Maybe the T4 autos use clutch cutout when the driver manually downshifts under WOT conditions. _________________ Casey--
'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik? |
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22639 Location: NYC/Upstate/ROW
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Posted: Tue Jul 17, 2018 10:15 am Post subject: Re: A/C cut off relay |
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I’ll look in my turbo beetle stick diagram to see if it’s a VAG thing
My Beetle is a very masculine dark blue, so it’s not a girl car.
My girl car diagram shows the AC clutch is controlled by the cooling group relay, which receives mutiple inputs from ECM and other sensors.
So, no TCM to cut out relay there. _________________ .ssS! |
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Broseph Stalin Samba Member
Joined: March 28, 2018 Posts: 433 Location: Colorado
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Posted: Tue Jul 17, 2018 2:00 pm Post subject: Re: A/C cut off relay |
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njt1rider wrote: |
So I sold my tdi swapped 93 weekender. I never got around to diagnosing why the a/c didn't work. I lived in it for 3 years with no a/c . Talking to the new owner today I was trying to help him solve the issue. Open up the bentley and within 5 minutes I find that there is a clutch cutoff relay on the auto van that isn't present with a manual. It appears that the relay just needs to be removed and hardwire the clutch wires per the schematic. Doh! Feel pretty silly now but here's my question:
Why do the autos have an a/c cut off relay that gets a signal from the tcm and the manuals just don't have the relay?
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Can you elaborate on this? I'm trying to get my '95 autotrans AC working. Looking at the diagram, I believe the J246 relay is the "38" relay on the fuse panel.
I've been underneath the van, nice shiny 1-yr old compressor, green/brown wires going into it, I meter zero voltage at the green/brown with the dash AC control ON.
I replaced the "140" relay with a new VW part (PN 701-959-141-B), still no 12v. The 30A fuse is good, the fan operates in AC mode, there is refrigerant in the system. _________________ '68 Bus in West Germany, 1977-1979
'67 Riviera poptop conversion in the US, 1984-1990
'95 EVC Winnie, 2018, Sold
'03 EVC Winnie, 2018, Sold |
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Zeitgeist 13 Samba Member
Joined: March 05, 2009 Posts: 12115 Location: Port Manteau
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Posted: Tue Jul 17, 2018 4:06 pm Post subject: Re: A/C cut off relay |
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I see the early T4s use a nearly identical pressure/temp switch as my T3. This could very well be your culprit.
_________________ Casey--
'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik? |
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Broseph Stalin Samba Member
Joined: March 28, 2018 Posts: 433 Location: Colorado
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Posted: Tue Jul 17, 2018 4:32 pm Post subject: Re: A/C cut off relay |
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Zeitgeist 13 wrote: |
I see the early T4s use a nearly identical pressure/temp switch as my T3. This could very well be your culprit.
[pic] |
Where is that bugger located? _________________ '68 Bus in West Germany, 1977-1979
'67 Riviera poptop conversion in the US, 1984-1990
'95 EVC Winnie, 2018, Sold
'03 EVC Winnie, 2018, Sold |
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njt1rider Samba Member
Joined: August 18, 2013 Posts: 62 Location: Louisville, KY
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Posted: Tue Jul 17, 2018 5:16 pm Post subject: Re: A/C cut off relay |
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The cut off relay is in position number 30. Sounds like you need to do some general troubleshooting before throwing random parts at it. (Much cheaper)
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njt1rider Samba Member
Joined: August 18, 2013 Posts: 62 Location: Louisville, KY
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Posted: Tue Jul 17, 2018 5:19 pm Post subject: Re: A/C cut off relay |
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That pressure switch is on the a/c hardlines coming out of the firewall on the passenger side under the hood |
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Broseph Stalin Samba Member
Joined: March 28, 2018 Posts: 433 Location: Colorado
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Posted: Tue Jul 17, 2018 6:31 pm Post subject: Re: A/C cut off relay |
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njt1rider wrote: |
The cut off relay is in position number 30. Sounds like you need to do some general troubleshooting before throwing random parts at it. (Much cheaper)
[pic] |
Thanks. I do have a 30 relay. As for general trblshooting with the AC I'm lost. I really don't mind throwing random parts in, I rarely do that.
I'm stuck right now because I don't want to tear the dash apart to find why I don't have 12v at the compressor 2-pin. I'm at a point where I'm eliminating simple things even if it costs $100 _________________ '68 Bus in West Germany, 1977-1979
'67 Riviera poptop conversion in the US, 1984-1990
'95 EVC Winnie, 2018, Sold
'03 EVC Winnie, 2018, Sold |
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njt1rider Samba Member
Joined: August 18, 2013 Posts: 62 Location: Louisville, KY
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Posted: Tue Jul 17, 2018 8:01 pm Post subject: Re: A/C cut off relay |
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There are a series of switches the signal needs to go through before it hits the clutch. The cut off relay is only one of them. PM me your email address and I'll send you the schematic. Tracing the wires are only half the problem as you will need to check that all the switches are working at the proper pressures including the relay and a/c module. The first thing I would do is jump the wires at the trinary pressure switch and see if the clutch turns on and the system blows cold air. If you have that then I would say there is a problem with the relay/control module/ switch/ or broken wire. |
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MasterMarine Samba Member
Joined: October 30, 2006 Posts: 8 Location: Now serving Snohomish County, WA
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Posted: Sat Aug 20, 2022 3:05 pm Post subject: Re: A/C cut off relay |
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I am not getting 12 v at my compressor clutch on my 2002 VW EV. I do not have the Climatronic. It is a Weekender. Does anyone have the wiring diagram? I have the Bentley but can't access it since I don't have an operational XP computer anymore.
Fuse is good. Relay 140 looks good inside for me.
Any tips? Wiring diagram? _________________ MasterMarine
2002 VW MV Weekender
2004 VW Jetta GLS TDI |
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MasterMarine Samba Member
Joined: October 30, 2006 Posts: 8 Location: Now serving Snohomish County, WA
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Posted: Sat Aug 20, 2022 6:57 pm Post subject: Re: A/C cut off relay |
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MasterMarine wrote: |
I am not getting 12 v at my compressor clutch on my 2002 VW EV. I do not have the Climatronic. It is a Weekender. Does anyone have the wiring diagram? I have the Bentley but can't access it since I don't have an operational XP computer anymore.
Fuse is good. Relay 140 looks good inside for me.
Any tips? Wiring diagram? |
I found the issue. There is a fuse (#19 - 10amp) for the aux coolant pump that also is involved in some of the fan / AC / AC Clutch control wiring. I found another post on here where someone mentioned it. I thought I had not heard that pump run after shutdown for a while so checked the 10a fuse. It was popped. I found the aux coolant pump was locked up. I disconnected the wiring to it then put in a new fuse. Made the AC system normal again and guess what? The AC clutch operated. Hooray.
I ordered a replacement aux coolant pump to install later. I also found a vacuum line disintegrated where it connected to the passenger side end of the intake manifold. It is in a tough to get to spot kind of behind a plastic vacuum actuator. The other end of it went to a right angle plastic white connector on the side of a 1/2" or so plastic tube running across the back of the intake parallel to it.
Thank you everyone for sharing info. You never know how it will help someone out! _________________ MasterMarine
2002 VW MV Weekender
2004 VW Jetta GLS TDI |
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