P38A P38 Compressor wont start automatically

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P4wn33

Member
Posts
24
Location
Germany
Hi!

I apologize in advance for my simple words but my English is not the best

We have an Range Rover P38 2000 4.6 with 245.000km in Germany. In 2021 we buyed an new Compressor from DUNLOP and it works for 15000km completly automatically. But few weeks ago the compressor wont start to work.. I tried with the Nanocom to start them, no reaction.. Replaced the relay, no reaction... test the relay, the relay works.. We checked the connection to the main unit (ANR4499) under the driver seat (LHD), the connection is okay, so we replaced the main unit and yeah it works.. after 5km again... its really confusing for me.. The last idea we have is to let the compressor work on its own, with new cables to the relay and his own pressure switch.. but this is really the last option.. Did you have any Ideas?
 
First check the thermal switch in the compressor. Should be an orange wire that is grounded by the thermal switch inside the compressor. If this is open circuit the ECU will not trigger the relay to run the compressor. Next try bridging the relay contacts which should run the compressor even if the thermal sensor is open circuit.

Also buy or make the EAS diagnostic cable, and download EAS-Unlock. If the ECU is in fault state it often will not run the pump.

Without diagnostics you are flying blind, and will spend money unnecessarily.
 
This is an EAS problem...yes?
Why did you buy a new compressor, was the old one not creating enough pressure?
The compressor won't run under certain circumstances (door open, overheat etc.)
Have you looked in the technical archive on here at the EAS related entries?
Good Luck. :)
 
pwood999 said:
First check the thermal switch in the compressor. Should be an orange wire that is grounded by the thermal switch inside the compressor. If this is open circuit the ECU will not trigger the relay to run the compressor. Next try bridging the relay contacts which should run the compressor even if the thermal sensor is open circuit.

Also buy or make the EAS diagnostic cable, and download EAS-Unlock. If the ECU is in fault state it often will not run the pump.

Without diagnostics you are flying blind, and will spend money unnecessarily.
Click to expand...

oh yeah I forgot something... .-. The Nanocom says the compressor is on.. okay I will try it thank you!
 
DanClarke said:
This is an EAS problem...yes?
Why did you buy a new compressor, was the old one not creating enough pressure?
The compressor won't run under certain circumstances (door open, overheat etc.)
Have you looked in the technical archive on here at the EAS related entries?
Good Luck. :)
Click to expand...

yeah it is an EAS problem.. its right the old compressor was only creating less 4 bar..
I looked many hours but I found nothing like this..
 
pwood999 said:
First check the thermal switch in the compressor. Should be an orange wire that is grounded by the thermal switch inside the compressor. If this is open circuit the ECU will not trigger the relay to run the compressor. Next try bridging the relay contacts which should run the compressor even if the thermal sensor is open circuit.

Also buy or make the EAS diagnostic cable, and download EAS-Unlock. If the ECU is in fault state it often will not run the pump.

Without diagnostics you are flying blind, and will spend money unnecessarily.
Click to expand...


okay I found the orange wire and connect it to ground.. its Open Line I will replace then.. but where is that switch?
 
DanClarke said:
See this to check.
Click to expand...


okay.. I installed the old compressor, which was perfect except for the fact that it can no longer build up the pressure. The thermal switch works and it's still the same problem.. Nanocom says compressor is on but it isn't.
 
P4wn33 said:
okay.. I installed the old compressor, which was perfect except for the fact that it can no longer build up the pressure. The thermal switch works and it's still the same problem.. Nanocom says compressor is on but it isn't.
Click to expand...

If you force the pump on using the Nanocom does it run? Cannot remember which menu but maybe under Utilities? If not then dodgy connector / wire somewhere.
 
Grrrrrr said:
If you force the pump on using the Nanocom does it run? Cannot remember which menu but maybe under Utilities? If not then dodgy connector / wire somewhere.
Click to expand...
thats under output and that's what I always do. But I tried with a jumper as relay the compressor start..
 

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P4wn33 said:
thats under output and that's what I always do. But I tried with a jumper as relay the compressor start..
Click to expand...
Right so if the jumper makes it run because it puts power to the compressor it means the thermal cutout is OK and not tripped, so something is inhibiting the power from being sent to the compressor.
So it is being "inhibited" what is the status of the inhibit switch?
 
DanClarke said:
Right so if the jumper makes it run because it puts power to the compressor it means the thermal cutout is OK and not tripped, so something is inhibiting the power from being sent to the compressor.
So it is being "inhibited" what is the status of the inhibit switch?
Click to expand...

The inhibit switch is working fine, says the nanocom
 
P4wn33 said:
The inhibit switch is working fine, says the nanocom
Click to expand...
Yes, that's the inhibit switch testing OK. But the EAS will also NOT run if there are doors/tailgates open etc. these conditions prevent the ECU from issuing a "run" command to the pump and it won't fire the relay to put power to the pump.
If you bridge the relay, does the pump run?

AND: If it does run, then swap the relay you just removed with another (many of them are the same), it could be that the relay has failed (they are German ;-) ).
 
Last edited:
DanClarke said:
Yes, that's the inhibit switch testing OK. But the EAS will also NOT run if there are doors/tailgates open etc. these conditions prevent the ECU from issuing a "run" command to the pump and it won't fire the relay to put power to the pump.
If you bridge the relay, does the pump run?
Click to expand...

Nanocom says all doors/tailgate are closed. I set the Jumper on R20 and it works

The picture is copied from the internet.
 

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