P38 Air Suspension Problem

Oldpilot said:

Kurt has been in touch.

I don't really want to throw money at this P38 as it is coming up to MOT in April and I am away until then.Owned it for ten years and put 150k on the clock for £4.5 when I bought it in 2006. It appears to me the compressor has failed and triggered some sort of low pressure signal to the electronics? No suck from the inlet when the filter is removed and no power to the plug side so something has clicked out.The kit and renovation appears quite simple but how about resetting the system to get the power back to the plug. Another light, TP?, has lit up on the panel?

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TC maybe don't recognise a TP. Fitting a new compressor maybe your best option. .

TC it is. What does that mean?

Is the compressor switched off by the system once it no longer produces pressure?

I don't understand why there is no power coming in to plug connection.

Oldpilot said:

TC it is. What does that mean?

Is the compressor switched off by the system once it no longer produces pressure?

I don't understand why there is no power coming in to plug connection.

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The compressor relay is pulled by the ECU only if the thermal switch is sound or is not open circuit because of heat build up and the pressure sensor shows low pressure. Do the checks outlined in the how to to check thermal switch. If there is no continuity through thermal switch to ground, between Orange wire and Black wire on plug, the ECU will not pull the compressor relay. If your compressor runs and sounds like a bag of spanners it needs stripping to find out why. TC is traction control sometimes comes on if battery is low could be a few causes.. Get compressor sorted worry about TC later it may go away when battery is fully charged. When you start up after car has been stood a while you will get ABS lamp and TC lamp on, TC lamp should go off when ABS pump has pressurised system to minimum operating pressure. Read and understand the How to reference compressor circuit everything is covered in that.

Thanks for the reply. I am starting to get my head around this now. The good thing is I leave for two months abroad today so plenty of time to read up on the system before tackling the job late March.

Oldpilot said:

Thanks for the reply. I am starting to get my head around this now. The good thing is I leave for two months abroad today so plenty of time to read up on the system before tackling the job late March.

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The ECU needs two things before it will power the compressor relay. It needs a closed circuit through the thermal switch to ground. And a low pressure signal from the pressure switch. When the compressor temperature exceeds 120 degrees the thermal switch goes open circuit, in which case the ECU will not pull the relay even if there is a low pressure signal. When the compressor cools the thermal switch goes closed circuit and the ECU will then pull the relay providing there is a low pressure signal. If the thermal switch has failed open circuit the ECU will never pull the relay.