eas compressor

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g1no

New Member
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7
hi there, im new to landyzone.
ive recently brought a p38 4.6 hse 1996, with an air suspension fault. The faults were.... needed new rear air bag, but the previous owner didnt bother replacing the bag, he put his own valves on each bag and locked the car in manual and bridged the eas ecu. When i got the car i replaced the rear air bag (all other bags were new and had recently been replaced), brought a replacement eas ecu with same part number as previous eas ecu. No faults were showing on dash anymore but there is no power going the air compressor, i have tested the compressor and it ran when i put a live and a negative to it but it wont run when its connected to the car, can anyone help me please????
 
hi sorry if this sounds daft but dont no where to find the relay, im a bit of a novice when it comes to cars just trying to familerise myself with this range. Their quite a car!!!!!!!
 
If the compressor runs jumped it sounds like the thermal switch has failed. When you jump compressor you must be very careful NOT to connect + or - to thermal switch signal wire or you will burn switch out. If thermal switch circuit is open the ECU will not power the relay.
 
hi wammers thx for that, could you tell me where the thermal switch is located and is it easy to replace?
 
my friend tested my compressor for me the first time but i think he put a live connection from the battery to the orange wire instead of the green one, would this cause the thermal switch to burn out? (the plonka told me he knew what he was doing) its only after i spoke to someone else they told me to put a live to the green and a negative to the black. once i done this the compressor fired up but like i said it wont when connected to the car?
 
ok, so i'l buy a switch tomorrow, hopefully i'l be able to change it myself and all fingers crossed she should rise like a trooper!!!
 
g1no said:
my friend tested my compressor for me the first time but i think he put a live connection from the battery to the orange wire instead of the green one, would this cause the thermal switch to burn out? (the plonka told me he knew what he was doing) its only after i spoke to someone else they told me to put a live to the green and a negative to the black. once i done this the compressor fired up but like i said it wont when connected to the car?
Click to expand...


Yep that would do it.
 
thought you could bypass the thermal switch by earthing the orange wire? thermal switch on fleabay about £9 last one I saw,bit of a fiddle to fit,I had to drill out the brush plate retainers and use small pop rivets when reassembling.Hope this helps.regards
 
tomcat59alan said:
thought you could bypass the thermal switch by earthing the orange wire? thermal switch on fleabay about £9 last one I saw,bit of a fiddle to fit,I had to drill out the brush plate retainers and use small pop rivets when reassembling.Hope this helps.regards
Click to expand...


The orange wire from the thermal switch is in circuit with a positive feed from the relay. It sends a feed back to the ECU to make the relay activation circuit. If there is no circuit through it, the ECU cannot activate the relay. The positive power feed from the relay feeds back to the ECU through the orange wire. This makes the ECU circuit to feed to the relay activation circuit, switching the positive power from the battery to the motor. If the thermal switch is open circuit there is no feed back to make the circuit in the ECU so the relay cannot be pulled in. That is why the compressor will run when the relay socket is jumped but cannot be run by the ECU. Not an easy to follow explination maybe, but if you look at the circuit diagrams all will become clear.
 
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tomcat59alan said:
you lost me Wammers:confused: hence the question mark after the first sentence.:)
Click to expand...

OK for simplification the thermal switch being open circuit deactivates the relay pulldown circuit.

Relay pulldown comes from pin 8 on ECU to pin 1 on relay 20, and is grounded through pin 2 on relay 20. With relay pulled down current then passes from fuse 40, 40amp through relay, in via pin 3 and out through pin 5 to compressor motor. This also puts power from negative side of motor through thermal switch to pin 16 on ECU. If no power is detected at pin 16 the ECU switches power off at pin 8. Deactivating relay. Providing motor is ok in compressor. The following checks can be done. Remove relay and feed pin 1 + and pin 2 - relay should click and there should be continuity across pins 3 and 5. Relay OK. Feed pin 5 + on socket, motor should run. Motor OK. Check continuity from green wire to orange wire. No continuity. Thermal switch duff. Continuity thermal switch OK. If all checks OK, ECU should be able to run compressor unless there is a pressure switch fault as the pressure switch also deactivates power to pin 8 ECU, pin 1 relay to stop motor when tank is full.
 
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thank you for that,Im now back on the whiskey.I have earthed the orange wire when i had a problem with the thermal switch and the compressor ran.Bit of a dark area for me ,electrics. Cheers:)
 
tomcat59alan said:
thank you for that,Im now back on the whiskey.I have earthed the orange wire when i had a problem with the thermal switch and the compressor ran.Bit of a dark area for me ,electrics. Cheers:)
Click to expand...


Yes that is possible because the thermo switch takes it's connection from the motor negative side. That would indicate that the motor earth point is faulty. Sorry i did not make that plain in description of circuit. Have ammended description for clarity.
 
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