A/C Clutch won't engage-relay good now
07-29-2009, 11:05 PM
#1
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A/C Clutch won't engage-relay good now
Hi All,
Well I have the common a/c clutch won't engage problem. However, mine appears to be a bit different.
I pulled the controller and checked the relay and found that terminals 5 & 6 were open energized or de-energized. Installed the radio shack relay and cured the open.
The clutch still doesn't work, there is no power on either side of the relay in the controller. I traced it back on the wiring diagrams to G86, and weld point 8, points somewhere on the car.
I think welding point 8 is supplying the power to the relay contacts for the clutch. Does anyone know where that is located on the car???
Well I have the common a/c clutch won't engage problem. However, mine appears to be a bit different.
I pulled the controller and checked the relay and found that terminals 5 & 6 were open energized or de-energized. Installed the radio shack relay and cured the open.
The clutch still doesn't work, there is no power on either side of the relay in the controller. I traced it back on the wiring diagrams to G86, and weld point 8, points somewhere on the car.
I think welding point 8 is supplying the power to the relay contacts for the clutch. Does anyone know where that is located on the car???
07-29-2009, 11:58 PM
#2
Team Owner
try jumping the low pressure switch on the side of the receiver drier.
Do search far Wallys tips and read how the A/C system works.
Or google 928 keepers
Do search far Wallys tips and read how the A/C system works.
Or google 928 keepers
07-30-2009, 05:52 PM
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Wally, It's a 1990 S4.
Alan, The blower fan works and the controller lights up. You can hear the cooling fans in the engine bay come on when the A/C switch is pushed also.
Alan, The blower fan works and the controller lights up. You can hear the cooling fans in the engine bay come on when the A/C switch is pushed also.
07-30-2009, 09:13 PM
#6
Electron Wrangler
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The AC switch must be plugged in or the relay will not engage - the illumination I referred to was on the AC switch not the head unit... Its easy to knock the connector off the switch - but if the AC on does trigger the Fans - it suggests the switch works since thats what drives it.
G86 goes to the ECU to tell it to boost at idle to compensate for the AC load.
Power is fed from the Fresh Air Blower relay at CE pin L23 - check Fuse 20 if this is inoperative.
Test the head unit in circuit - monitor the relay in at L23 and the relay out - after the freeze switch at G21.
If you have power at L23 and no power at G21 check the freeze switch operation - if there is no power to either terminal on the freeze switch you may have incorrectly connected the relay..?
Check the connections to the head unit are all mounted securely...
Alan
G86 goes to the ECU to tell it to boost at idle to compensate for the AC load.
Power is fed from the Fresh Air Blower relay at CE pin L23 - check Fuse 20 if this is inoperative.
Test the head unit in circuit - monitor the relay in at L23 and the relay out - after the freeze switch at G21.
If you have power at L23 and no power at G21 check the freeze switch operation - if there is no power to either terminal on the freeze switch you may have incorrectly connected the relay..?
Check the connections to the head unit are all mounted securely...
Alan
07-30-2009, 09:18 PM
#7
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Power for the A/C starts at Terminal 87 on the Blower Relay - Relay XII. If the blower works, this relay is OK.
From the relay, it goes to welded point #8. This isn't accessible.
From point 8, it goes to Terminal 9 of the A/C push button switch on a red/white wire. Power here will tell you whether or not welded point #8 is OK. (Ignition switch on, HVAC bottom lever on the first position - a square block, which is dash outlets).
If there is power on Terminal 9, push the button and check for power on Terminal 8, with one or two Green/blue wires. If the cooling fans come on, there is almost certainly power on Terminal 8, as this is the trigger for those fans. If there is power here, there should be power at the A/C relay in the control head.
From Terminal 8 on the switch, power goes to Terminal 7 on the control head on a Green/Blue wire. If there is power on Terminal 7, and it makes it thru the connector, and then thru the diode, there will be power on the relay.
It sounds as if you have power to the A/C switch at least.
From the relay, it goes to welded point #8. This isn't accessible.
From point 8, it goes to Terminal 9 of the A/C push button switch on a red/white wire. Power here will tell you whether or not welded point #8 is OK. (Ignition switch on, HVAC bottom lever on the first position - a square block, which is dash outlets).
If there is power on Terminal 9, push the button and check for power on Terminal 8, with one or two Green/blue wires. If the cooling fans come on, there is almost certainly power on Terminal 8, as this is the trigger for those fans. If there is power here, there should be power at the A/C relay in the control head.
From Terminal 8 on the switch, power goes to Terminal 7 on the control head on a Green/Blue wire. If there is power on Terminal 7, and it makes it thru the connector, and then thru the diode, there will be power on the relay.
It sounds as if you have power to the A/C switch at least.
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07-31-2009, 07:45 PM
#8
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Ok, I'm a dummy....
I miswired the new relay and read it out while it was hooked up to the car.
Wired the realy right and all is well. Compressor kick on and the whole bit.
I do have foamy at the site glass.
Where is the low side connect to charge the 134a on a 1990 S4? I'm not seeing it.
D
I miswired the new relay and read it out while it was hooked up to the car.
Wired the realy right and all is well. Compressor kick on and the whole bit.
I do have foamy at the site glass.
Where is the low side connect to charge the 134a on a 1990 S4? I'm not seeing it.
D
08-02-2010, 09:10 PM
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08-02-2010, 10:30 PM
#12
The low pressure side chargine valve is accessable, however, there is a few hot thing around there, like the top radiator hose.
Got scorched, would advise your wear long sleeves.
Some members have made extension pieces to this valve which make it far more accessable.
Tails 1990 928S4 Auto
Got scorched, would advise your wear long sleeves.
Some members have made extension pieces to this valve which make it far more accessable.
Tails 1990 928S4 Auto
08-02-2010, 10:37 PM
#14
Chronic Tool Dropper
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There's some discussion in several threads, as well as in the AC workshop manual supplement, about liquid charging a system without starting the engine at all. No muss, no fuss, no burns. Worth a try IMHO.
08-02-2010, 10:41 PM
#15
Race Car
The low pressure side chargine valve is accessable, however, there is a few hot thing around there, like the top radiator hose.
Got scorched, would advise your wear long sleeves.
Some members have made extension pieces to this valve which make it far more accessable.
Tails 1990 928S4 Auto
Got scorched, would advise your wear long sleeves.
Some members have made extension pieces to this valve which make it far more accessable.
Tails 1990 928S4 Auto