A/C Compressor wiring? EDIT: Shop set car on fire
05-02-2007, 01:11 PM
#1
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Thread Starter
A/C Compressor wiring? EDIT: Shop set car on fire
I had to have A/C last summer so I took the car to one of those foreign repair shops 
. I showed up one day to check on it and they were having trouble keeping it running, they said the coil was bad and they replaced it, they also said that the wiring harness was messed up and they repaired it. My compressor turns on and off when the car is running. It looks like they just wired the compressor straight from the coil to always stay on? Is normal compressor operation on and off? I am going out to inspect the wiring harness for the damage...
. I showed up one day to check on it and they were having trouble keeping it running, they said the coil was bad and they replaced it, they also said that the wiring harness was messed up and they repaired it. My compressor turns on and off when the car is running. It looks like they just wired the compressor straight from the coil to always stay on? Is normal compressor operation on and off? I am going out to inspect the wiring harness for the damage...
Last edited by whitefox; 05-02-2007 at 01:54 PM.
05-02-2007, 01:53 PM
#2
Banned
Thread Starter
Well I am quite surprised, upon inspecting the wiring harness, they set my car on fire. I can't beleive I didn't notice it sooner, the coolant tank is black!!!! I don't know what to do at this point... I think a visit to the shop is in order. Any advice would be great.
I just called the repair shop, I talked to the mechanic and he says he replaced the coil but "nooooooooo we would never alligator clip anything" he went on to tell me that the reason the car was acting up was because the coil had to be standing upright and it was upside down, and I told him the coil lays horizontally, he said something about the fluid in the coil, I hung up on him. I paid these guys $750 dollars to replace a pipe that goes to the rear A/C. $513.50 in labor and $180.25 to have the pipe repair by another shop.
I just called the repair shop, I talked to the mechanic and he says he replaced the coil but "nooooooooo we would never alligator clip anything" he went on to tell me that the reason the car was acting up was because the coil had to be standing upright and it was upside down, and I told him the coil lays horizontally, he said something about the fluid in the coil, I hung up on him. I paid these guys $750 dollars to replace a pipe that goes to the rear A/C. $513.50 in labor and $180.25 to have the pipe repair by another shop.
Last edited by whitefox; 05-02-2007 at 02:12 PM.
05-02-2007, 02:07 PM
#3
Man of many SIGs
Rennlist Member
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Ross,
I think you will have great difficulty getting them to do anything about this since its almost a year later. I suppose it can't hurt to try. Be polite and firm. Good luck.
On an unrelated note. Have you gotten the key yet? Give me a call.
I think you will have great difficulty getting them to do anything about this since its almost a year later. I suppose it can't hurt to try. Be polite and firm. Good luck.
On an unrelated note. Have you gotten the key yet? Give me a call.
05-02-2007, 02:18 PM
#4
Captain Obvious
Super User
Super User
It's hard to tell but I don't think the car was set on fire. The coolant tank is black but thre is no visible (from the picture) sign of an actuall fire. The coolant tank can have dark deposit on the inside or soem heat damage fromthe engine on the outside. If there was fire, all the wire insulation would be the first to go and I can't see any sign of that.
05-02-2007, 02:57 PM
#6
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Thread Starter
The damage done doesn't seem to be too bad, the wiring harness is cripsy and the coolant tank is burnt a bit. I don't think I'm going to be able to do anything about it. I needed to replace the coolant tank anyway.
Back to the A/C wiring... I disconnected that aligator clip and compressor doesn't turn on. I can't find any hacked wires, where should I look?
Back to the A/C wiring... I disconnected that aligator clip and compressor doesn't turn on. I can't find any hacked wires, where should I look?
05-02-2007, 04:26 PM
#7
Three Wheelin'
There are several switches (e.g., high pressure, low pressure, freeze switch) which could keep the compressor from receiving power.
The compressor can cycle on and off given too much or too little pressure, or if the air becomes too cold for too long and risks freezing the evaporator.
Does the AC compressor run all the time? Or only with the AC switch pressed in? It should not be wired to run all the time and defeat the other switches that are inline for a reason.
I'm sure some of the resident AC experts will chime in. There will be a lot of things to test, in the proper sequence, but it shouldn't be all that difficult if you have gauges and a multi tester.
The compressor can cycle on and off given too much or too little pressure, or if the air becomes too cold for too long and risks freezing the evaporator.
Does the AC compressor run all the time? Or only with the AC switch pressed in? It should not be wired to run all the time and defeat the other switches that are inline for a reason.
I'm sure some of the resident AC experts will chime in. There will be a lot of things to test, in the proper sequence, but it shouldn't be all that difficult if you have gauges and a multi tester.
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05-02-2007, 05:32 PM
#10
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The compressor should only run with the AC switched on. Once the cabin is cooled to the desired temperature, the compressor cycles to maintain the temp. Also, if the evaporator becomes too cold, the compressor cycles.
I'm not too sure on the 928, but on some vehicles, the AC compressor generates a tach signal when spinning. If the signal disappears, then the clutch is disengaged. This is incase the compressor seizes, so other accessories can continue functioning.
I'm not too sure on the 928, but on some vehicles, the AC compressor generates a tach signal when spinning. If the signal disappears, then the clutch is disengaged. This is incase the compressor seizes, so other accessories can continue functioning.
05-02-2007, 05:36 PM
#11
Banned
Thread Starter
The compressor cycles on and off in ~30 second intervals, it blows cool air out the front, if i turn the rear A/C on, the front will just blow warm air while the back blows cold. "American Foreign Automotive" is the name of the place.
05-02-2007, 06:36 PM
#12
Three Wheelin'
Originally Posted by ben12345
Once the cabin is cooled to the desired temperature, the compressor cycles to maintain the temp.
05-02-2007, 06:39 PM
#13
Under the Lift
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If it cycles on and off, it is probably either the freeze switch or low-pressure switch. You can put a jumper wire in their plugs one at a time and see if it is one of them. If it stays on after you bypass one of the swtiches, that's it.
You need to find some 928 buddies in your area, like Tampa 928s, who will help you avoid any more ignorant butchers.
You need to find some 928 buddies in your area, like Tampa 928s, who will help you avoid any more ignorant butchers.
05-02-2007, 08:38 PM
#14
Banned
Thread Starter
There is no power to either of the freeze switch terminals. Where to check next? Time to check the relay right? Any good write ups for checking this?
Last edited by whitefox; 05-03-2007 at 12:01 AM.
05-03-2007, 04:52 AM
#15
Ross,
A fault finding process to check electrical system of your A/C.
Go onto 928 Specialists web site and download their fuse and relay chart for your car (1987 S4)
1. Disconnect negative terminal from battery
2. Remove relay IV (Ignition Relay X)
Check continuity of terminal 30 and 87 by supplying 12 volts to terminal 85 and connect 86 to earth and whilst having an ohm meter across terminal 30 and 87 and see whether you have a circuit.
Remove 12 volt supply and you should have an open circuit as the relay solonide coil is de-energised.
If no circuit replace relay
If OK proceed to next step.
3. Check fuse 6 A/C fuse (5 amp) (visual inspection, ohm meter or via fuse tester if fitted to Central Electrical Panel - this will require the battery to be connected). If fuse is OK then proceed to next step.
4. Reconnect battery
5. Turn on ignition and this should connect 30 bus to the A/C Control Switch.
6. Turn on A/C switch.
7. Disconnect twin spade connector from Thermo Switch Evaporator Protection and connect a volt meter between spade connector on the twin wire (violet wire with green strip) and earth. You should get around 12 volt depending on the state of charge of the battery.
If you don't get 12 volt then you have a continuity problem between fuse and A/C control switch, the A/C on/off switch and Thermo Switch.
8. Check plug T29 which is a 4 terminal plug (unfortunately my 1987 wiring diagrams do not have the location field, however my 1990 S4 it is indicated location as 8cN) which should be behind the passenger side panel of the central consol). Remove side panel by removing two phillips headed screws and you should locate the 4 terminal plug at the front end near the A/C foot well air outlet.
Disconnect plug and check that all terminals are clean and bright and all wires are connected to the terminals. The positive wire is via terminal 2 of plug T29 which should also be a violet with a yellow strip wire on the A/C control switch side of the plug joining to the violet with white stripe wire to the thermo switch side.
Disconnect plug and check whether you have 12 volts from the control switch side of the plug to earth via a volt meter. If you have then the A/C control switch circuit, including the A/C on/off switch is OK and the fault is in the circuit from the plug to the thermo switch.
To check the continuity of this wire, connect the ohm meter to the spade connector of the wire at the Thermo Switch and earth the other end to earth. If you don't get an infinity reading then you have a short in this wire (set ohm meter to maximum setting and with an open circuit you should get a reading of 1). When you connect the ohm meter to the spade and the other end to earth the reading should remain 1, if you get a lesser reading you have a short circuit. Connect the ohm meter to terminal 2 of plug T29 and the other end to the spade connector and you should get a lower ohm reading which means that the continuity of the wiring is OK
You will need to track this wire between the terminal plug T29 and the thremo switch connection to find the earth or fracture. You may find the fault where it passes through the fire wall or any other area where the wire may have been rubbing against a hard circuit or if it has overheated and burnt through the insulation and is shorting or the wire could be broken.
If the fault has not been located here with a 12 volt supply reading then the next step is:
9. Remove the drivers side panel from the Central Control Console and remove the plug connector from the A/C on /off switch and by using a ohm meter check the operation of the switch by connecting the ohm meter between terminal 8 & 9 ( the red and white stripped wire terminal and the black wire with the blue stripe terminal). With the ohm meter connected push the switch on and off and confirm that you have a circuit when the switch is on.
If you still do not have 12 volts present then proceed to next step.
10. Locate terminal 7 on A/C control switch and check that you have 12 volt supply. Check this with the volt meter connected between terminal 7 and earth. If 12 volt is not present then check for shorting or continuity of this wire via the ohm meter as previously described.
If there is still no 12 volt supply then move to the next step.
11. Locate terminal 10 on A/C control switch and determine whether you have a 12 volt supply. If you have 12 volt supply then there is most probably a fault within the A/C control switch circuitry or in the wiring between fuse 6 and terminal 10 via plug T30.
12. Check wiring between fuse, plug T30, terminal 1 and the from plug terminal 1 to terminal 10 on the control switch. T30 plug is a 6 terminal plug and should be located adjacent to T29 plug on the passenger side of the central console. Disconnect T30 plug and check all terminal plugs are clean and bright and all wires are connected.
Using the volt/ohm meter between terminal 1 of T30 plug (Black wire with white stripe) on the fuse side of the plug check for 12 volts, continuity test and short circuit test. If loss of continuity or short circuit indication then check wiring for burning, insulation wear, cracking etc. Repair fault/s.
13. If the compressor clutch is still not engaging then the circuits from the inlet to the thermo switch to the compressor clutch are faulty.
If 12 volts is now available to the spade connector (the spade with two wires) reconnect to thermo switch, remove the other spade connector and check whether there is 12 volts from this connector to earth if 12 volts present then switch is OK, if not thermo switch is faulty.
14. If switch is OK, then move to the High Pressure, Low Pressure Switch located on the passenger side of the car just forward of the A/C condenser and liquid receiver. Disconnect the plug from the bottom of the switch and check for 12 volt supply via volt meter to both terminals connectors within the plug. If no 12 volts is located then there could be a fault within the wiring between the thermo switch and the pressure switch. Fault finding via visual, continuity or short circuit testing to be undertaken. If no fault is located then run a temporary wire from single spade connector to pressure switch and then determine whether compressor clutch operates with ignition on and A/C switch on.. This will indicate that there is a fault in the wiring.
15. If no fault located and clutch is still not engaging then with temporary wiring still connected check outlet terminal connector for 12 volts. If 12 volts present then pressure switch is OK and would indicate fault maybe between pressure switch and compressor clutch. This wire is a black wire via terminal 2 of plug T18 and then via a connector just before the compressor clutch. Disconnect T18 and check plugs etc as described above and check that you have 12 volts etc.
16. If no faults found and 12 volts present you have the wiring and the last plug before the compressor clutch to check. Undertake checks as described above and if 12 volts is available at last plug then the compressor clutch maybe at fault.
17. To check clutch operation, use the temporary wire as mentioned above and connect to terminal plug to clutch. Ensure that you do not connect to the earth wire of the clutch and the clutch should operate. If it does not then the clutch is at fault and may need replacing.
Initially this was to be a short process. Hope it will help.
Tails 1990 928 S4 auto
A fault finding process to check electrical system of your A/C.
Go onto 928 Specialists web site and download their fuse and relay chart for your car (1987 S4)
1. Disconnect negative terminal from battery
2. Remove relay IV (Ignition Relay X)
Check continuity of terminal 30 and 87 by supplying 12 volts to terminal 85 and connect 86 to earth and whilst having an ohm meter across terminal 30 and 87 and see whether you have a circuit.
Remove 12 volt supply and you should have an open circuit as the relay solonide coil is de-energised.
If no circuit replace relay
If OK proceed to next step.
3. Check fuse 6 A/C fuse (5 amp) (visual inspection, ohm meter or via fuse tester if fitted to Central Electrical Panel - this will require the battery to be connected). If fuse is OK then proceed to next step.
4. Reconnect battery
5. Turn on ignition and this should connect 30 bus to the A/C Control Switch.
6. Turn on A/C switch.
7. Disconnect twin spade connector from Thermo Switch Evaporator Protection and connect a volt meter between spade connector on the twin wire (violet wire with green strip) and earth. You should get around 12 volt depending on the state of charge of the battery.
If you don't get 12 volt then you have a continuity problem between fuse and A/C control switch, the A/C on/off switch and Thermo Switch.
8. Check plug T29 which is a 4 terminal plug (unfortunately my 1987 wiring diagrams do not have the location field, however my 1990 S4 it is indicated location as 8cN) which should be behind the passenger side panel of the central consol). Remove side panel by removing two phillips headed screws and you should locate the 4 terminal plug at the front end near the A/C foot well air outlet.
Disconnect plug and check that all terminals are clean and bright and all wires are connected to the terminals. The positive wire is via terminal 2 of plug T29 which should also be a violet with a yellow strip wire on the A/C control switch side of the plug joining to the violet with white stripe wire to the thermo switch side.
Disconnect plug and check whether you have 12 volts from the control switch side of the plug to earth via a volt meter. If you have then the A/C control switch circuit, including the A/C on/off switch is OK and the fault is in the circuit from the plug to the thermo switch.
To check the continuity of this wire, connect the ohm meter to the spade connector of the wire at the Thermo Switch and earth the other end to earth. If you don't get an infinity reading then you have a short in this wire (set ohm meter to maximum setting and with an open circuit you should get a reading of 1). When you connect the ohm meter to the spade and the other end to earth the reading should remain 1, if you get a lesser reading you have a short circuit. Connect the ohm meter to terminal 2 of plug T29 and the other end to the spade connector and you should get a lower ohm reading which means that the continuity of the wiring is OK
You will need to track this wire between the terminal plug T29 and the thremo switch connection to find the earth or fracture. You may find the fault where it passes through the fire wall or any other area where the wire may have been rubbing against a hard circuit or if it has overheated and burnt through the insulation and is shorting or the wire could be broken.
If the fault has not been located here with a 12 volt supply reading then the next step is:
9. Remove the drivers side panel from the Central Control Console and remove the plug connector from the A/C on /off switch and by using a ohm meter check the operation of the switch by connecting the ohm meter between terminal 8 & 9 ( the red and white stripped wire terminal and the black wire with the blue stripe terminal). With the ohm meter connected push the switch on and off and confirm that you have a circuit when the switch is on.
If you still do not have 12 volts present then proceed to next step.
10. Locate terminal 7 on A/C control switch and check that you have 12 volt supply. Check this with the volt meter connected between terminal 7 and earth. If 12 volt is not present then check for shorting or continuity of this wire via the ohm meter as previously described.
If there is still no 12 volt supply then move to the next step.
11. Locate terminal 10 on A/C control switch and determine whether you have a 12 volt supply. If you have 12 volt supply then there is most probably a fault within the A/C control switch circuitry or in the wiring between fuse 6 and terminal 10 via plug T30.
12. Check wiring between fuse, plug T30, terminal 1 and the from plug terminal 1 to terminal 10 on the control switch. T30 plug is a 6 terminal plug and should be located adjacent to T29 plug on the passenger side of the central console. Disconnect T30 plug and check all terminal plugs are clean and bright and all wires are connected.
Using the volt/ohm meter between terminal 1 of T30 plug (Black wire with white stripe) on the fuse side of the plug check for 12 volts, continuity test and short circuit test. If loss of continuity or short circuit indication then check wiring for burning, insulation wear, cracking etc. Repair fault/s.
13. If the compressor clutch is still not engaging then the circuits from the inlet to the thermo switch to the compressor clutch are faulty.
If 12 volts is now available to the spade connector (the spade with two wires) reconnect to thermo switch, remove the other spade connector and check whether there is 12 volts from this connector to earth if 12 volts present then switch is OK, if not thermo switch is faulty.
14. If switch is OK, then move to the High Pressure, Low Pressure Switch located on the passenger side of the car just forward of the A/C condenser and liquid receiver. Disconnect the plug from the bottom of the switch and check for 12 volt supply via volt meter to both terminals connectors within the plug. If no 12 volts is located then there could be a fault within the wiring between the thermo switch and the pressure switch. Fault finding via visual, continuity or short circuit testing to be undertaken. If no fault is located then run a temporary wire from single spade connector to pressure switch and then determine whether compressor clutch operates with ignition on and A/C switch on.. This will indicate that there is a fault in the wiring.
15. If no fault located and clutch is still not engaging then with temporary wiring still connected check outlet terminal connector for 12 volts. If 12 volts present then pressure switch is OK and would indicate fault maybe between pressure switch and compressor clutch. This wire is a black wire via terminal 2 of plug T18 and then via a connector just before the compressor clutch. Disconnect T18 and check plugs etc as described above and check that you have 12 volts etc.
16. If no faults found and 12 volts present you have the wiring and the last plug before the compressor clutch to check. Undertake checks as described above and if 12 volts is available at last plug then the compressor clutch maybe at fault.
17. To check clutch operation, use the temporary wire as mentioned above and connect to terminal plug to clutch. Ensure that you do not connect to the earth wire of the clutch and the clutch should operate. If it does not then the clutch is at fault and may need replacing.
Initially this was to be a short process. Hope it will help.
Tails 1990 928 S4 auto