I searched the AC threads and didn't see any discussion of this particular problem - hoping someone can help. We have a '95 RR 4.0 with about 125k miles. I've replaced the compressor and blend motors over the years and everything works fine with one exception. If the truck is hot and parked for a short period the compressor will not operate on restart. If the truck sits long enough to cool everything works fine. I'm assuming something is getting heat soaked and opening the compressor circuit. I initially suspected a relay or even the fuse block since I read they're prone to heat damage, but replacing those had no effect. The local dealer replaced the high pressure switch to no avail - then suggested a cracked block from overheating (detected CO in the coolant?). The truck doesn't overheat and runs perfectly. Any ideas?

 

I don't know how a cracked engine block would keep your AC from coming on, but you did find out one thing don't go back to that guy.
the fuse block, relay and high pressure switch were good calls; do you have a little note book on the face on the ac control panel?

 

The cracked block didn't make sense to me, either. I only use the dealer when I'm desperate, and in this case they appear to be clueless, too.

I did get the little notebook icon when the blend motor went south, but the control panel is clear and no fault codes associated with the compressor problem. I was wondering if the computer might take the compressor off line to reduce engine load when it senses an overtemperature condition - which would occur immediately after shutting the beast down on a hot day. Could it be something as simple as a temperature sender somewhere? The engine temp gauge seems to be functioning normally.

Appreciate your feedback.

 

unfortunately, I can answer either question.
You would think the ECU would be programmed to cut out the AC if the temperature got too high in order to lessening the load, But this is LR/ Lucas not much makes sense.

also if the temperature gauge/sending unit in the early P-38 is anything likes the ones in DII's it useless. on a DII the gauge will sit dead center from 160-235 degrees, you might want to check your real temp with an OBDII scanner.

the only other thing i could think to try to narrow it down would be running a temp. + feeder and next time it happens, put power to the compressor and see if the clutch kicks in.

 

Will do - at least that would eliminate the compressor as a possible culprit. Thanks.

 

drowssap - compressor clutch turned out to be the problem. Got the AC in the heat soak fail mode today and power switched properly to the clutch with the main AC switch. Not certain if that component can be replaced - suspect it's time for a new compressor. Thanks again for your feedback - should have started here in the first place.

 

you can buy just a clutch kit if you want, but "i" would just get a used compressor for Paul Grant, bolt it on and pay someone to evacuate it and charge the system. good luck