P38 weird suspension problem

Hi all, got a really odd problem with my p38
1998 2.5dse
the suspension pump will not run unless i connect a 12v feed to the purple/light green cable feeding it, the timer delay relay appears to be working and there is voltage going to the ecu, but there is NO trigger voltage though to R20 in the fuse box from the ecu, cabling all checks out ok, odd thing is as i drive it the suspension lamp flashes as if the ecu is doing its thing but the pump wont run, anyone come across the ecu failing but still appearing to be working??? any ideas or thoughts greatly appreciated

cheers in advance guys!!!

Check the pressure switch and the thermal cutout circuits. Pressure switch should have no continuity at low pressure below 8 bars and continuity when tank is full 10 bars. There should be continuity from Orange wire to Black wire on compressor. DO NOT put power to Orange wire you will fry thermal switch. Continuity test only. No continuity from Orange to Black, thermal switch duff.

Or run orange wire to earth,this will bypass thermal switch.If compressor runs switches are available on ebay,about £9

tomcat59alan said:

Or run orange wire to earth,this will bypass thermal switch.If compressor runs switches are available on ebay,about £9

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Alan just to clarify for those who may try this.
Not if you disconnect Orange wire and put it to earth it won't. Orange wire circuit comes from earth side of motor through thermal switch and to pin 16 on EAS ECU. If switch is duff with no continuity you are just connecting a wire to earth that isn't connected to anything at the other end. You must leave it connected to plug, break into it and run an earth, what you are doing is earthing pin 16 on ECU which enables circuit to pull in relay 20. A lot easier to do a continuity test. You should not be tempted to leave wiring in this state and run compressor for any length of time.

thanks guys much appreciated, will give it a go at the weekend and post the results

Hi guys checked it out and there is no continuity between orange and black, if i short the orange to earth the relay cuts in and the pump runs, so it looks like the thermal switch has died....problem is that i left the pump running for about 3 or 4 minutes but she didn't lift just sat there so could there be another issue that has effectively killed the thermal i.e valve block or something else?? thanks for your help so far...the saga continues.........

philco said:

Hi guys checked it out and there is no continuity between orange and black, if i short the orange to earth the relay cuts in and the pump runs, so it looks like the thermal switch has died....problem is that i left the pump running for about 3 or 4 minutes but she didn't lift just sat there so could there be another issue that has effectively killed the thermal i.e valve block or something else?? thanks for your help so far...the saga continues.........

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You will have to get a new compressor or refurb the old one first of all without air you can't get much further. Could be as simple as diaphragm valve stuffed or a bad leak which has caused excessive compressor running.

Hi guys..problem fixed!!!!! refurbed the comp and fitted a new thermal now runs nicely lifts as it should but unlevel but will fire up the modis and reset the heights over the weekend...thanks again for all your help

philco said:

Hi guys..problem fixed!!!!! refurbed the comp and fitted a new thermal now runs nicely lifts as it should but unlevel but will fire up the modis and reset the heights over the weekend...thanks again for all your help

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Well done that man.