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Discussion Starter · #1 ·
I understand that a 98 gt has a 2 spd cooling fan. Is it possible that as the engine temp rises above the temp that is supposed to change the fan from low speed to high speed operation that the fan would stop instead of making the transition? That appears to be what is happening as I can see the fan turn on as the engine warms up but, after a bit the fans stop and the vehicle overheats. What could be the possible cause. Also, what is the difference between fan high speed ect 1 "on" and fan high speed ect 2 "on"? The turn on and off points are the same at 208 and 200 degrees? Thanks.
 

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Discussion Starter · #3 ·
You misunderstood the question. I'm aware the fan is not "supposed" to stop. I was asking that when the fan is "supposed" to go from low speed to high speed what could possibly be wrong with the system that would cause the fan to stop. eg.fuse, fan controller or whatever. Sorry for the confusion.
 

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first thing check fuses if they are good time to start tracking wires the power comes from the fuse box accros the rad support to the pass fenderwell hooks to the ccrm the goes to the fan 3 wires to the fan 1 gnd 1 low speed and 1 high speed let me know if u need anything else
 

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Discussion Starter · #5 ·
Is there a seperate fuse for the high speed? Just see 1 fuse for the fan. The low speed works. Also, what is the difference between fan high speed ect 1 "on" and fan high speed ect 2 "on"? What does ect stand for. Why would there be "2 options" for the same thing? Those are programmable features for the Diablo Predator or SCT tuners.
 

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you can unplug the cooling fan resistor completely an it will only come on high speed. There is a noticeable sound difference between the two settings. with the fan on low speed you can hardly hear it inside the car, but when it kicks on high speed is when you can really hear it. There is only one fuse for the cooling fan that im aware of. The low speed is run off the resistor. It gets power from the same circuit as the high speed. I think your wiring is somehow messed up or maybe the fan itself
 

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There is a separate fuse (circuit breaker) for the LOW Speed fan. A single fuse supplies both the HS and LS fan. So the fact that the LS fan works means that the main fuse is working.

Run the fan directly from the battery using a jumpper wire. Test both the LS and HS fan. This will prove/disprove the function of the High speed fan motor.

If the fan motor is confirmed good, this may be a CCRM problem.
 

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My Diablo has the same parameters, not sure why there are two ECT hi on's. I just set them the same. ECT is the engine coolant temperature PID as provided to the PCM by, of course, the ECT sensor. Assuming your 98 is same as my 99, it's there on the top front left of the intake manifold.

When did this issue start? What values have you selected for the on/off settings, if you have changed them?

As wmburns said some jumping, testing, and tracing should get you to the bottom of this. Plugging in the Diablo will be handy to watch the ECT PID while you test. A multimeter will be nice too if it gets into circuit tracing. Do you have the circuit diagram? I can post it for 99 but no guarantee it will be identical.
 

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Discussion Starter · #9 ·
What I have done until I can have some down time (It's really my sons car) is, with the Diablo, program the high speed fan ect 1 &2 to come on at 280 deg, thus forcing the low speed fan (which we know works) to stay on continuously. Seems to be working out for us. What does CCRM stand for? Thanks all for the replies.
 

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There is a separate fuse (circuit breaker) for the LOW Speed fan. A single fuse supplies both the HS and LS fan. So the fact that the LS fan works means that the main fuse is working.

Run the fan directly from the battery using a jumpper wire. Test both the LS and HS fan. This will prove/disprove the function of the High speed fan motor.

If the fan motor is confirmed good, this may be a CCRM problem.
This just answered all my questions about my 98 Cobra Engine Fan. The rare times it goes to high speed. It sounds like a jet engine. It stays on high speed longer than expected. I only do short runs. Even when the car has been parked long enough to cool down it doesn't switch back til it is driven for a while or sits all night.
 

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