howdy all. i have an 04 chrysler crossfire that i have used as a daily driver for the past 2.5 years. it has 85k miles on it. my ac went out a year ago. dealership told me it would be $1,200 to fix. i held off an entire year and broke down and had them fix it earlier this month.
when i got the car back, air was fixed. only problem was the radiator fan was stuck on high. dealership cant figure out why. they took components out of another crossfire that was there and put them in mine. with those components, the radiator fan was still stuck on high. this led them to believe that it must be something internal in my crossfire. they said they think they know what it is but it will be $2600 to fix it. any help or suggestions here would be highly appreciated.
thanks!

 

The PCM ( Powertrain Control Module - in the black box by the battery ) monitors the A/C and the engine temp.
It in turn controls the FCM ( Fan Control Module - mounted on the driver side fender well ) to control the fan speed.

 

Ok, first: Stop taking your car to the dealer. Find a small independent shop known for expertise with MB products; taking a Mercedes to a Chrysler dealer is not productive if the dealer has no "Crossfire Tech".

Second: "USA" is not a location, if you change your profile to tell us where you are, we may have a shop for you to go to where you can get your car fixed.
For example: I live near Atlanta - if you are within 3 hours of ATL, I'd tell you to simply make an appointment with Buckhead Imports.

The radiator fan is SIMPLE:

The PTCM communicates it's desire for the fan to run over a single wire, bidirectional, Pulse Width Modulated data stream. When the PTCM wants the fan to run, it "tells" the Fan Control Module to speed it up. There is a two-way pulse sent back and forth, the PTCM 'pings' the FCM and the FCM pings back, indicating all is well.
If the communications break down between the FCM and the PTCM, two things happen:

1) The PTCM alerts you to a possible cooling system failure by turning on a small yellow indicator to the side of the instrument panel, it looks like a little radiator.
2) The FCM goes into "emergency mode" and spins the fan at high speed.

If you do NOT have the little light, my guess is that the FCM is bad. The modules run about $140 if I remember right.
If you DO have the light, you have a bad connection between the two modules or a broken wire.

The PTCM COULD be bad, but this would be a "first" that I've heard of in over four years on this forum. FCMs go bad kinda often.


But it IS that simple.

 

Before I paid $2,600 I think I would get a used Fan Control Module and try it.
Controller A025 545 59 32
eBay

 

^^^ Mr. Part Number shows up! ^^^

 

Yea, like I give a simple explanation, and Mark writes a friggin book
( however - I like yours better )

 

Some people say I need a girlfriend.






(I say that some girl needs me. )

 

Excellent write up on how it works and how to troubleshoot it!

 

It is if you are in the Witness Protection Program.

 

If that part of the car was working when you brought it to them and they gave it back in a non-working condition, they need to pony up the $2600 to have it fixed.

Or, you can take the info provided here to the Service Department and let them fix it "less expensively" but still on their dime. Tell them you did the leg work, now they can provide the part and labor and then you're even

Good luck

 

thanks for all the info everyone. ill get to fixing my location. im actually in greenville sc if you all have any sauggestions on good garages in the area.
also dealership replaced fan cooling relay, part number 5102818ab. any chance this is the same as the fcm, part number A025 545 59 32, that you all spoke of earlier?

and fan wasnt working at all when i brought it in so the stealership did not add a problem. just a heads up

 

Fan Cooling Relay? WHAT?

100/80 - you got any guesses as to what they are telling this person? A google search showed not ONE picture of that item.


Also, you didn't indicate if the little radiator light was on or not.

 

That is the same part but with the Chrysler (more$$$) part number.
The problem lies elsewhere then.

 

radiator light is not on. temp gauge is good. temp has always been good prior to this. only over heated one time sitting in bumper to bumper traffic. good fan would have turned on at that point prior to this im guessing.

i found a post on here that you replied on back in 08/2011. mechanic had same issue with a clients crossfire. based on that, the two differing part numbers, chrysler and mercedes, were deemed to be the same in that post.

found in that post that another mechanic installed a new radiator fan in the car and wired it improperly causing it to have fan stuck on high. mechanic asking the question on forum was then able to correct wiring and fix car.

fcm in my car is very clean, no engine dirt, im going to guess it was replaced by dealer.

everything else is fine in car. i looked at the wiring and all connections were good.

there is a mercedes specialist in town. probably going to take car there for second opinion

 

It IS the same part, it should show the Mercedes part number on it. No Chrysler number is shown on the part, only on your invoice. Mercedes price plus Chrysler mark up.

 

Ok, so this means the FCM is communicating with the PTCM.

Either the "new' FCM is bad OR the PTCM is bad.

But there is one OTHER possible answer: The PTCM is getting bad data from a sensor and it turning the fan on to try to cool the engine. I am reminded that, somewhere, I read that the sending unit for the gauge is NOT the sensor the PTCM uses to determine engine temperature. If THAT sensor is bad - there you go!

100/80 - am I right about this? (I'm almost 100% certain I am.) I have an ultragauge on my car and it's "coolant temperature" indication does not quite follow the gauge. I'm thinking the gauge is way too 'damped' or I am seeing the evidence for two sensors.

(You can put a scope probe on the PWM line and look at the length of the pulses and know right away what the PTCM is telling the FCM. Lotsa luck finding a guy at a dealership that has an oscilloscope and knows how to use it.)

 

Typically modern automotive systems have a seperate sender for the temp gauge, which is a pretty rough signal meant to give an approximate visual representation of whatnthe cooling system is doing. The ECM/PCM have a sender of their own that is typically quite fine, allowing the module to read in tenths of degrees for fine fuel system changes and things like enabling cooling fan modules and so on. Typically gauge senders are single wire, utilizing a block ground for its signal while a PCM sender will have 2 or 3 wires, varying a voltage reading instead of a ground.
A decent scanner should help troubleshoot if this sender is malfunctioning or not. Just look for a live signal option and find coolant temp. Compare it to the gauge, best to do it with the engine cold so you can see a large differential if the sender is malfunctioning.

 

^^^ Which the Ultragauge will do ^^^

 

i googled the ultragauge. tell me more about it please

 

Get one!

Total fun toy and you never need to wonder what code is set. Also, you can look at any of up to 54 sensors that the PTCM is watching. I'd bet if you put an UG on your car, the "Coolant Temp" reading will be way high. This means that the PTCM is not at fault, the temp sensor is. Then, you order one and either change it yourself or take the car to a local trusted guy and just tell him, "Put this in." You pay no diagnostic fees. If it fixes it, fine. If not, you did not spend $2000, either.

But with the UG, you know so much more about what is going on than without it.

Mine is stuck to my windshield and snitching to me about what is going on with the car every time I drive.