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maelstrompat

New Member
Bear with me...bit of a novice.
Hoping Wammers may pick up this thread...... :)
(I am sure that other SM's are just as intelligent and may also wish to contribute!)
'95 P38a eas compressor will not cut in, will if I jump the relay.
Recon compressor fitted.
Double checked pump by connecting a third to check thermal switch. OK
New pressure switch fitted.
New air dryer fitted.
Relay at ECU checked & OK.
Power to ECU OK.
Changed relay at fusebox.
Pump also runs from Easi-unlock.

Now running out of ideas, have checked many threads and RSW info.
Help!
 
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Thinking it may be the engine bay fusebox. Had no heater for many years and today (after being under the lid for quite a while) changed a heater relay with a spare relay I bought for the EAS and Whoops! I have now got heat ~ the Wife is delighted:angel:

Have had the fusebox out and checked the connections underneath and all looks OK and, I suppose if the compressor works by hot-wiring the relay, the fusebox must be OK but to be frank I have no idea what other fusebox probs there could be.
 
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You say you have checked the thermal switch, have you tried bypassing it by grounding the orange(?) wire....

This need to be dine by leaving it all plugged in and trimming back the sheath a tad and attaching a wire to earth!

Wammers will be able to clarify.....
 
Saint.V8 said:
You say you have checked the thermal switch, have you tried bypassing it by grounding the orange(?) wire....

This need to be dine by leaving it all plugged in and trimming back the sheath a tad and attaching a wire to earth!

Wammers will be able to clarify.....
Click to expand...

My local garage (Power Crazy Motorsports) put a multimeter on the Orange wire today and said it was OK but I don't think they attached a wire to earth and as I said, we also borrowed another pump which was certified OK (thermal switch etc.) and had the same prob.
 
Could it be a dodgy connection to the pressure switch? I assume you had to tease the connector out of the connector block when you put the new one in?
 
Grrrrrr said:
Could it be a dodgy connection to the pressure switch? I assume you had to tease the connector out of the connector block when you put the new one in?
Click to expand...

Now there's a thought.......brand new one went in but if the connection was duff in the first place I'd still have the same prob. Thanks, I'll check that out.
 
maelstrompat said:
Now there's a thought.......brand new one went in but if the connection was duff in the first place I'd still have the same prob. Thanks, I'll check that out.
Click to expand...

Compressor will run through EASunlock without a good thermal switch or pressure switch, so check the connections to the pressure switch. If all good check the thermal switch. Should be continuity between Orange wire and Black wire. If there is switch is good if none it's duff. If pump is run off car, DO NOT put power to Orange wire. Or you will instantly blow thermal switch.
 
Datatek said:
Maybe there is full pressure in the tank and the fault lies elswhere?
Click to expand...

Maybe, but i get the impression the car is on it's knees but the compressor won't run. The compressor circuit is pretty simple low or no pressure on, pressure off. I presume new relay at ECU will be delay timer. Needs to check a few things, pressure switch should be open circuit with no pressure. Continuity Orange wire to black wire on compressor. All relays and fuses good, F24, F44 engine bay and F17 in BECM. Obviously MF2 relay 20 and compressor ground are ok or compressor could not be forced on. If all is good with pressure switch and thermal switch it is down to ECU not pulling relay 20 for some reason. Maybe stating the obvious but compressor will not run unless engine is running. :)
 
Datatek said:
Maybe there is full pressure in the tank and the fault lies elswhere?
Click to expand...

Could well be the case. Reason I mention the fusebox is due to serious water leaks running down door pillars and other areas. Under carpet NS front wet floor (noticed when checking ECU). We did check the bulkhead for wire chaffing from compressor to ECU but seemed OK. If we hot-wire the relay we get a full tank of air OK, we did have a slight leak at top of OS airbag ~ now sorted. Air tank drain plug removed and tank is dry, did that before fitting air dryer.
 
maelstrompat said:
Could well be the case. Reason I mention the fusebox is due to serious water leaks running down door pillars and other areas. Under carpet NS front wet floor (noticed when checking ECU). We did check the bulkhead for wire chaffing from compressor to ECU but seemed OK. If we hot-wire the relay we get a full tank of air OK, we did have a slight leak at top of OS airbag ~ now sorted. Air tank drain plug removed and tank is dry, did that before fitting air dryer.
Click to expand...
Look at the connectors behind the kick panel in the NS footwell.
 
Wammers, in your experience have you had a situation where there was a bad connection at the pressure switch causing a similar fault to mine?

Thanks for your input BTW.
 
maelstrompat said:
Wammers, in your experience have you had a situation where there was a bad connection at the pressure switch causing a similar fault to mine?

Thanks for your input BTW.
Click to expand...

As far as i am aware the pressure switch has a simple on/off function. Open circuit at below around 116-24 psi and closed circuit at around 140-150 psi. So if there is no circuit (bad connection) the only thing that can happen is the compressor would not stop. If thermal switch checks out as described, pressure switch is open circuit, relay is good (proved by forcible running from diag). Then you are looking at ECU for some reason not pulling relay, when everything else is set fair for that to happen. Multimeter time.
 
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wammers said:
As far as i am aware the pressure switch has a simple on/off function. Open circuit at below around 116-24 psi and closed circuit at around 140-150 psi. So if there is no circuit (bad connection) the only thing that can happen is the compressor would not stop. If thermal switch checks out as described, pressure switch is open circuit, relay is good (proved by forcible running from diag). Then you are looking at ECU for some reason not pulling relay, when everything else is set fair for that to happen. Maybe it is not getting an engine running signal. Multimeter time.
Click to expand...

Hard to believe there are no faults logged, that's why I speculated that the tank might be full.
I agree about the multimeter, on the pressure switch for starters.
With the OP's comments about water coming in, I would also be looking at the signal from the EAS ECU to the relay and the connectors en-route.
 
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