I suspect my fan relay module has failed.

Are they the same for all Crossfires? I have a 2005 SRT6, but would one from a 2004 manual car work?

Thanks!
Brian

 

The FCM does fail, but the fan MOTOR seems to fail more.
What symptoms you got?



And I am 99% sure all FCMs are the same... I bet 100/80 will chime in and set us strait.

 

Been having some electrical gremlins. I didn't drive the car for about three months because I was traveling, and the battery failed and took out the alternator with it, really the voltage regulator probably (my bad, I should've disconnected the battery). I replaced the battery and alternator (that was a fun experience, nice to know they used two different alternators, and that they are not interchangeable as the diameter of the pulley shaft is different on both models....GRRRR).

After that I got a CEL for the coolant level sensor, but when I checked it, it was fine, so I drove it as it didn't over heat until I got stuck in traffic and it did then.

I found that the electric fan wasn't coming on. I read through the threads here and saw that if you turned on max AC that the cooling fan was supposed to come on, and that was a good test to determine if the fan was working, but there was a chance it could be the fan relay module as well. I tried that, and no fan. I put in a new fan, and got the same results, so I'm thinking it's got to be the fan module. There's one on fleabay now, so I was thinking of grabbing it and seeing if that resolves the issue. I did use a volt meter on the fan module and could see voltage from the tiny wires that go into it, but nothing every came out of it.

I'm totally open to ideas

Also I tried to hook my Harbor Freight ODB2 reader to my Crossfire to see if it would give me a code for the CEL, but I get an error that it cannot connect, yet in my other car it connects fine....could just be that it's an inexpensive ODB2 reader....but I dunno.

 

Yea, the coolant light can mean several things. Sounds like the ECM lite the coolant light because it can't talk to the Fan Module.
I know for a fact that if the ECU can't get a response from the fan module (the ECU "tickles" the Fan Module several times a second), it lights the coolant light.

On the OTHER hand, if the Fan Module does not feel the tickle, it puts the fan motor into emergency mode. That is, the module turns the fan on 100% full, since it is then not gettting instructions from the ECM as to how warm the coolant is getting.

To summarize: There is a single wire running from the fan module to the ECM. This is a bi-directional bus, pulses from one module are felt by the other module and if this communication breaks down, and IF both modules are healthy, then the ECM lights the Coolant light and the Fan Module turns the fan on fullly.

Yup, sounds like you have a bad fan module.

 

Thank you for the details, this is very helpful.

So the 2004 manual trans fan module will work on a 2005 SRT6 auto car? There's one on fleabay for $85, so I was thinking of grabbing it.

Thanks again!
Brian

 

Short answer is a question, is it the same part number? My SRT uses A 025 545 59 32.
I'm not sure as the SRT has an extra wire or two that are not inside the plug, my 2004 NA did not have these wires. where they go I'm not sure.

 

It's the same part number. I know the wires you're talking about, they're small copper wires, like old telephone wire that aren't actually in the fan relay wiring harness, they're kind of outside. No idea what they do either, but the part on fleabay is the same part#. I'll take a look at the module on my SRT6 and see what's the deal with these extra two wires on the outside of the module.

Thanks,
Brian

 

My '05 Limited uses the same one.

 

Interestingly the gentlemen I purchased the replacement fan control module from is a MB tech. He had this to say about troubleshooting the issue and thoughts about what's the most probably real culprit, the ECM (god I hope not, that will be an expensive repair ):

"yes if put on max ac the fan will run only if the high side pressure reaches a certain threshold like 350 lbs,375lbs,etc just depends on model of car. anyway a few checks you can do in a few minutes with a volt/ohm meter would be,with key off, unplug the connector at the pwm (should have 6 wires). the sockets are number on connector. socket # 3 is 12 volts and socket # 2 is ground. sockets #1 & #4 go to fan,can test for continuity with ohm meter to fan connector for each wire to make sure there is no broken wire. socket #6 is switched power(12 volts with key on). now if those are all in order the next step is socket #5 -this comes from your engine control unit/fuel management cu this is a pulse width modulated signal that cannot be measured with a normal volt meter. this requires a scope to see. this is the magic that tells when and how fast the fan needs to run to the module you bought from me. note- if socket #3 is not 12 volts with key off -there is a 50 amp fuse blown. like i said before usually if the fan module is bad the fan runs 100% (limp mode). usually if i see coolant light on dash and fan inop its likely an expensive engine control module. that would suck because you can not use a used part -those need to be a virgin part and then coded to car. just do the test to see if it is something stupid. then i hope my gut feeling is wrong."

 

All I know is that about 10 people here have had a bad fan motor, about 2 or 3 have had a bad FCM - but I don't remember ANYONE needing a PTCM/ECM to fix a fan that would not run or ran too fast.

 

Your numbers on the people with fan and fan control problems is waaay too low. I'd guess way more than ten times what you quote. Of course you're still a newby. LOL

 

I hope you guys are right, I really don't want to dump $2K into this car right now if I don't have to

I should have the FCM in a day or two, looks like it'll take all of about 2 minutes to swap out, but I'll check the test points he referenced to see what it shows before swapping it out.

 

I swapped the FCM tonight, no love, CEL still on, and no fan

Does it take a while for the CEL to clear?

Is there a way to reset/reboot the ECM, like disconnecting the battery for 24 hours?

Thanks,
Brian