I have the same problem my is an international checked the wiring everything good checked the fuse its good too what can it be???
I have a 379 Peterbilt. I am having problems with my engine fan and my ac compressor. Neither of them are working correctly. If I run a ground to the compressor it will come on but it will not cycle. Same for the engine fan if I run a ground to the fan solenoid on the firewall the fan will come on. These problems occurred after swapping engines but kept the original ecm and wiring harnesses.
Well lets start with what you swapped from and to, what the donor engine came out of and if you re-used the original engine's ECM/reprogrammed the new engine with the old engine's parameters.
Both engines are mxs cats. I used the original ecm and yes sir I have had it reprogrammed. I will also tell you that I’ve tried using the donor engines ecm and still have the same problem. Someone just told me to try the trinary switch. Any thoughts??
What did the replacement MXS come out of? Unfortunately I no longer have any access to Caterpillar service info. Does the fan function correctly when the engine temperature rises? Does it operate from the manual switch (if you have one)?
It came out is a 05 Peterbilt mine is an 06. The fan dose not work at all unless I run a ground to the solenoid and even then it doesn’t come kick off and on as it should. It just stays on.
Sounds like possibly the ECM is the component that commands ground for the solenoid when the fan is required. I'm not really leaning towards an ECM issue since you had the same result with 2 ECMs and you said the one with the replacement ECM had the configuration copied over from the old one. Is it possible the harness got pinched or damaged during the swap? Maybe try and trace the harness from the solenoid back to the ECM and see if you can spot any obvious damages. Maybe give the wires a gentle pull at all connectors. Most wires should be able to handle an 8-10 lb tug without breaking.
That’s what I lean towards myself. I may have to just take the harness off and open it up so I can really look it all over
Sorry I can't be much more help. I don't have access to any Caterpillar service info anymore unfortunately so I can't tell you specifically which wire in the harness controls the fan.
