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InterTech, Technician
Category: Heavy Equipment
Satisfied Customers: 21
Experience:  2008 Navistar certified. 7 years working for an International Dealership. Cummins ISX & ISM cert.
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I am working on a 2004 volvo vnl 760 semi. I have a problem

Customer Question

I am working on a 2004 volvo vnl 760 semi. I have a problem with the engine fan constantly running. I tried replacing the air solenoid on back of trans. This did not fix the problem. The truck has a volvo engine. I do not have a power and ground at the AMDM at pins b and e. I have power at e but no ground at b. What should be the next step in diagnosing this problem?All fuses were ok in dash.
Submitted: 8 years ago.
Category: Heavy Equipment
Expert:  InterTech replied 8 years ago.

The ecm controls the engine fan. That's why you have no ground . Is your truck equipped with a A/C? If yes, you should check the high pressure switch; if it's defect , the fan will stay on. Locate the switch, betwwen the a/c compressor and the expansion valve, unplug it and jump the two terminals. If it was the problem the fan should go off. You can replace it without emptying the system. Other wise, what does your coolant temperature gauge reads?? do you have a check engine light on?? You said you replkaced the solenoid on the back of the tranny??? I'm not familiar with volvos but the solenoids for the engine fan are located on or near the firewall... Let me know.


Customer: replied 8 years ago.
On a 2004 Volvo semi there is an AMDM (air management distribution unit) located on a crossmember behind the trans. There are about 5 different solenoids that screw into it and control various air functions. One of which is the engine fan. (you can blow shop air into the line and the fan will disengage) I understand the ground comes from the ecm. However with a pro-link hooked up to the truck the ecm shows the fan is off. So either I believe the ecm is either not grounding the solenoid or I have a problem with the wiring between the AMDM and the ecm. Yes the truck is equipped with AC and no I have no check engine lights or active codes.
Expert:  InterTech replied 8 years ago.
Ok! it,s like International's RASM (remote air solenoids module) but we're not controling engine fan with that. Anyway, it should work the same way; is the other accessories on the AMDM working properly? If not the module itself is probably defect; I saw lots of module getting water infiltration and not working on one or all of the solenoids. Problems in the wiring sets fault codes usually. Check your high pressure switch on the A/C first to make sure. If the pro-link displays fan off then the ecm is sending the signal to the amdm, and if it's working like International, it is communicating on the J1939 datalink. At the AMDM connector, you should have a green and yellow wire; check the resistance between those 2 terminals by backprobing, key off; you should read 60 ohms. if you read 120 ohms you're missing a terminating resistor and it is the problem. Let me know .... Yannick
Customer: replied 8 years ago.
I will check this out when I get to work tommorrow and get back to you