EAS Compressor will not power on its own

Hello,

I have a '97 P38 that I am working on and have the strangest issue. The EAS Compressor will not power on under normal circumstances as it should. When I jump the wires at the fuse box underneath the bonnet it will kick on. When I send a signal via the functional test on the RSW Solutions software (a laptop connected to the OBDII socket) it will kick on. Even when I ground the connection via power probe at the EAS ECU connector it will kick on. In all cases it will not turn off on it's own will.

I have replaced the EAS Compressor with a brand new one and have also changed the EAS ECU with a known functional one and still I have the same problem. As a last resort I even purchased another BECM and Engine ECU (used of course) thinking that maybe something was wrong with the BECM but that did not make it change at all either! I don’t suspect a continuity issue with the wiring or wiring harness as the other tests proved to kick on the compressor.

Any ideas on what the issue might be? I read online here the pressure relief valve on the EAS Valve Block may have seized functioning therefore not allowing the compressor to kick on but I am not sure if that’s the case but I have gone ahead and ordered that part as well.

Any help is greatly appreciated! Thank you!

-Calguy

Possible Pressure switch failure in the valve block or the Orange Thermal Switch wire in the connector would be my first thoughts....

Thank you Saint.V8, I'll replace the pressure switch. Is the Orange Thermal Switch wire bypassed when the eas compressor is turned on by jumping the wires at the relay?

Best,

Calguy

calguy said:

Thank you Saint.V8, I'll replace the pressure switch. Is the Orange Thermal Switch wire bypassed when the eas compressor is turned on by jumping the wires at the relay?

Best,

Calguy

Click to expand...

I believe the Thermal cut out is bypassed in that instance....

It is a common thing that to bypass the Thermal Cutout to mask an issue is to cut small slither of the insulation on the Orange Wire and then attach a fly lead to ground....

If your Orange Wire is frayed or snapped somewhere, the Compressor won't run normally as the ECU thinks it has overheated.

Try grounding this Orange Wire (with the electrical connector still plugged in) and see if the compressor cuts in correctly...if it does it could be the Orange wire is open circuit somewhere or both compressor you have tried have duff thermal switches...

If this doesn't work, my second guess is the Pressure Switch telling the ECU the Tank is full when it isn't and hence why the pump won't run!

Thank you Saint.V8. I will try testing the Orange Wire as you have described. Unfortunately, it's not the pressure switch as I just replaced that today as you mentioned. I'm hoping it's the Orange Wire at this point since everything else has been tested and/or changed!

I will report back with an update soon.

Best,

Calguy

Are all the doors and tailgate closed properly ?

ovalandrover said:

Are all the doors and tailgate closed properly ?

Click to expand...

As above and also check the underbonnet fuse box for signs/smells of burning.
Randomly changing ECU's is not a good idea.

Yup, all doors and tailgate are properly closed. No burnt smells from the fusebox but the relays do look "old" and show slight discoloration on the top of them. However I haven't taken the fusebox apart. Could there be a problem with it? What should I look for on the internals of it?

Thanks,

Calguy

calguy said:

Yup, all doors and tailgate are properly closed. No burnt smells from the fusebox but the relays do look "old" and show slight discoloration on the top of them. However I haven't taken the fusebox apart. Could there be a problem with it? What should I look for on the internals of it?

Thanks,

Calguy

Click to expand...

Try swapping the EAS compressor relay for another of the same colour.
If the connection pins on the relays are discoloured, it's likely the fuse box is toast.

Datatek said:

Try swapping the EAS compressor relay for another of the same colour.
If the connection pins on the relays are discoloured, it's likely the fuse box is toast.

Click to expand...

I did that already; I swapped another relay in the place of the compressor and no change occurred. The pins on the relays are not discolored, the top plastic housing on some of them are however.

Calguy

I'd go thermal switch. The printed board by the thermal switch is CR@P! I've seen it melt before the thermal switch before. Check it isn't broken anywhere and solder a wire across if it is. I posted a pic on here a while back showing what happened to mine.