relay and wiring weirdness

[jdog]

Try swapping relays if you haven't already done so

[Pete M]

I've swapped them back and forth and swapped in known good ones. 

[OptimusPreem]

Has this unit had any other weird electrical issues? I'm not too familiar with the CRD, but could it be a faulty TIPM?

[mjeff87]

Yeah.....fan should not be running continuously.  Do you also have a mechanical fan on yours?  Being a diesel I imagine you would, but I dunno.  Only the "heavy duty"/towing package 3.7's got a mechanical fan also (mine does not have one).

 

Those relays are controlled by the ECM.  The only trouble I ever had with that circuitry (and it really wasn't THE actual problem) was when my alternator died.  It threw a code for bad fan relay.....go figure.  Gotta love 2000-era DC electronics.  Try turning out your dome light.....that might fix it 

 

edit:  just spitballing here, but 2 other things come to mind.  The fan relays get energized by two things:  A/C operation and/or engine temp.  A/C operation is obvious, to control head pressure in the condenser.  Try unplugging the high-side pressure switch and see if the fan turns off.....switch may be stuck "on" sending a signal to the ECM to energize the fan.  On the temp, it appears there are actually 2 different inputs to the ECM for this.  One is coolant temp, which should be above 230F for the 2.8.  The other temp input is battery temp (the sensor under the battery tray).  From reading, if it senses less than a certain battery temp (I think it's low, like 15 degrees), it sends a signal to the ECM to not energize the fan.  I'd check both the coolant sensor and the battery temp sensor to see if either is messed up.

 

Or, like I said, it could be something completely unrelated, like the dome light.  Lol.

[Pete M]

I've had a thought that maybe this is normal, or at least the weirdest part of it.  maybe the computer has a fail-safe where if one relay dies, the other kicks on automatically.   I've put the word out to my fellow CRD enthusiasts to check what happens when they pull a relay.  If that's true and normal, then I can skip on to diagnosing why the fans don't activate when they should be.   

 

Or just wire in another relay so lo-speed is all the time and the hi-speed function is on a separate switch. 

 

oh, and yes, CRDs all had mech fans and e-fans

[mjeff87]

I wish I knew more about the CRD's.

 

Wanna talk weird electrical stuff?  Changing the fuel filter on the Focus last weekend, I pulled the 15A fuel pump fuse to run it and depressurize the system (like normal).  It keeps running.  So I put it back in and pulled the relay....and it still kept running.  I actually had to pull both the fuse and the relay to kill power to the pump.  I'm not even sure how that's even possible.  No shorted/crossed wires anywhere, either.