A few days ago, I started up the Crossfire and before I got out of the driveway, the elec. fan came on. The temperature is not even showing a temperature yet, and the coolant is full. I unplugged the fan relay and the fan stopped, but when I plugged it in, the fan came back on. I replaced the fan relay, this worked for about 1 minute. The elec. fan came back on and runs all the time until I shut off the key. The air cond. is off. Any ideas?

 

Resolder the Relay Control Module. https://www.crossfireforum.org/forum...-no-start.html

 

Is the car running other than that? I mean, does the engine start and run?

 

Another question: Is this light on?

 

The car runs great, and no lights are on. And I replaced the relay control module. The temperature gauge does not go above half way regardless of how long I drive it. It just started this one morning.

 

None of this makes sense. The engine cooling fan (we ARE talking about the engine fan, right?) system is very simple. The ECM tells the Fan Module how fast to run the fan. It starts the fan up at about 180F water temp, by the time you get to around 210F, the fan is running at 70-80% speed.

If you turn the A/C on, the fan will run at about 120 rpm unless the engine is getting warm, then it will speed up as described above.

If the fan module and ECM can't communicate, two things happen:
1) The ECM lights the "low coolant" light to indicate that you should go to a dealer with a blank check, a jar of vasoline and a receptive attitude to spending money.
2) The Fan module enters "emergency mode" and spins the fan at 100% warp drive speed to protect the engine.



Ya got me on this one.

 

[SIZE="3"]Could this be the problem, maybe? Coolant temp. sensor

 

I suspect the fan control module has a shorted switching transistor, causing the fan to run, you can measure the fan voltage. I have found 4 volts for normal operation, whats your?? WOddy

 

He says he replaced the 'fan relay' I think that mean the fan control module.



If he changed a relay, then he changed the wrong part - and in that case I'd bet on your theory, Woody.

 

Marc, does the signal from the ECU to the fan control module vary in voltage according to how fast it needs the fan to turn? I realize the voltage directly to the fan will vary for speed, but how is the module told to turn on, slow or fast? Just curious.

 

IT is the width of the pulses from the ECM that tells the FCM how fast to turn the fan. The "voltage" on the wire is either at 0 or 5 volts. The time spent in either state is what conveys the informatoin. A voltmeter will read oddly, a 'scope will show you what is going on.


For example, the fan would run slower with the 20% trace, faster with the 80% trace.
With the 100% trace the fan would run at full speed, but not due to the constant high, since their are no pulses at 100%, the fan would be in emergency mode.

80% is the closest to normal "full speed" of all traces shown below.

 

Ok thanks. What about reading it with an analog volt meter?

 

YOu cna't tell what is going on. An RMS meter (you can google that) won't interpret the pulses for you.

 

You can see if it is modulated with a rms meter. a meter with RMS or root mean square relationship is an AC meter. Looking at the signal in AC and DC range will give an indication of the signal.

IF it is DC your dc reading will some value and the AC reading will be close to zero, if it is PW modulated, the AC reading will be signficant though the reading will be largely meaningless as it is a square wave pulse, but your note the AC nature. The meter can not be a harbor freight meter as its AC scale will read DC in one direction as its a half wave rectifier and if reversed on DC it will read nothing.

Sorry for the tech talk mumbo Jumbo. If you have a fluke meter the motor voltage will be metered in both DC and AC. Bottom line, was the relay or module replaced??

On day two of car ownership I checked my module and found it was digitally controlled by the computer, and I did no more with it. Plannned on controlling the speed but digital and me are not on speaking terms. WW

 

I was trying to post a picture of the fan relay, but it wanted to put post a giant picture. But, when I start the car, it fires right up. By the time I put the top down, the elec. fan is running. (Engine Fan) The fan comes on slowly, then picks up speed and within 15 - 20 seconds the fan is running at what I think is 100%. I just ordered a new ECM, when that comes in, I'll let you know if it worked.

 

Where the hell did you get an ECM?


You say that like you were ordering a headlight - ECMs, so I am told, are close to $2000.

 

Post the picture anyway please.

 

I have found an ECM, or powertrain control module, from $1,800 - to under $200. This is that fan relay I replaced. I figured out how to attach a picture.

 

Just keep in mind that ECMs are coded to the VIN. If you buy a used one, it must be remasked (if that can even be done).

And that is a photo of the Fan Control Module. There is no relay in it.

 

Hopefully that is a GOOD, properly working FCM that you replaced the old one with.
I know you said the temp. gauge seems o.k., but have you considered that it might possibly be a sticky gunked up thermostat? How many miles on the car? Have you ever flushed the coolant or checked the old thermostat? Just looking for an easy button here for you.