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1996 Mustang GT Electric Fan Problems

10230 Views 7 Replies 2 Participants Last post by  jaredm_k
Hi everyone - New to this board and having trouble with a 96 GT I just bought. I know that the CCRM is notorious for failing on these things - but if I am reading the diagrams correctly and testing it correctly....I believe it is good. So here is my logic - please tell me if I am wrong. There is a green and purple wire coming from the PCM into the CCRM that would basically be ground wire...causing the relay to close and run the fan. I jumped a wire from the negative side of the battery to that green and purple wire and my fan came on....that should mean the relay in the CCRM is good, right? If the CCRM is right, that means it either is the PCM or one of the sensors that sends a signal to the PCM, right?

I've been staring at this all day, and wanted to make sure I was on the right track...because I feel like I could be spinning my wheels and not getting anywhere.

Any help would be appreciated. Thank you!
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You are making this tooooo hard to start with by failing to mention some details. Like for example, what is the problem/symptom?

Remember that the GT uses a two speed fan. IMO the best 1st test is to CONFIRM that the fan actually works on BOTH speeds. This will determine what the next test should be.
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Sorry - So I just bought this 96 GT and on the way home it appeared to be getting too hot (only an idiot gauge but still figured the "A" in normal is not "normal" operating temp). So I stopped and left the car running, got out and noticed the fan wasn't on. So that is when I started testing things.

As I mentioned before I was able to ground the green wire coming from the PCM and get the high speed fan to kick on. I thought the low speed fan was coming on with the AC so I didn't test that....but I'm out in the garage right now and I tried to ground the blue wire coming from the PCM that runs the low speed and I couldn't get it to kick on.

While I was out here, I disconnected the ECT right behind the thermostat housing and the fan kicked on low for maybe two seconds and then kicked on high. So that is where I am.

Sorry I wasn't detailed enough the first time, if you guys have a second to give me advice I would appreciate it!

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So here is an update. I took a gamble yesterday and bought the CCRM module based on all the other reading I was doing on the forums. No luck. Still the same problem. Also, now when I unplug the ECT behind the thermostat, the low fan kicks on and the immediately shuts off. This thing is giving me a headache.

Any ideas on what to test/replace next?
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On the 98 and older model year there is a separate temperature sensor for the PCM and the dash gauge.

For the 99+ model year, the ECT sensor goes straight to the PCM. The PCM "tells" the dash what to display.

Question. Does the motor actually overheat?

For the 98 and older MY's, there's the possibility that there's a difference in calibration between the PCM ECT and the dash temperature gauge.

I assuming that you have confirmed that the fan motor itself does run on both speeds directly from battery power. I could see if someone replaced a GT fan with a V6 fan it could cause the reported symptom.

Also note that there are differences between the CCRM's. There are model year differences as will as engine (V8 verses V6). Confirm that the correct CCRM has been used for your model year and engine.

Regarding testing the CCRM. For the 96 MY, the low speed control wiere is DB. The high speed control wire is LG/P.

Grounding the high speed control wire (LG/P) should cause the high speed fan to run.

However grounding the low speed control wire (DB) may not work as you think. Why? Because on some MY's, the circuit is designed to work in a "fail safe" mode. As such, the logic is reversed. To run the low speed fan requires the DB wire to be "open". Grounding the DB wire will cause the fan NOT to run.
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I've always shut the motor off before it gets too hot. So no, it has not overheated....I'm not sure if it would or not....and I'm not willing to let it run that long. I suppose I should hook up a mechanical gauge to get an accurate temperature reading.

I have ran jumper wires from the battery to confirm that it works. Both low and hi speeds.

Noted on the low speed fan circuit being different. I knew it looked different on the wiring diagram with it going through some kind of box before entering the relay.

Not sure what I will try next at this point.
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Does the motor overheat if driven for a long expressway trip? Or does it only get hot if driven say below 35 MPH?

An easy way to confirm the motor's temperature is to point an infrared temperature gun at the T-stat housing.

Does the system hold pressure?

How do the fan bearing feels? Does the fan spin freely by hand?
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So I have only driven the car 15 miles since I bought it. When I thought it was getting hot I didn't want to continue to drive it. So now when I am testing it, I am letting it sit in my driveway. But when I noticed the overheat on my drive home, it was when I was just getting off the freeway, sitting at a stop light.

I don't have an infrared temp gun, maybe the parts store has one that they use.

What's the easiest way to see if the cooling system is holding pressure?

The fan spends free by hand.

Last night I replaced the ECT sensor right behind the thermostat housing. That didn't seem to fix it either. The good news is that the check engine light came on, so perhaps it will throw a code that will give me a hint as to what to look for next. Have to take it over to O'reilly's tonight and have them run the scan on it.

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