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Old 08-27-2010, 07:17 AM
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Engine Coolant Fan

1999 Grand Cherokee Loredo 4.0

Car overheated the other day while bride was idling in a parking lot for (what she claims) 5 minutes with the A/C.

Normally the car maintains around 210 very well....but she stated the guage went to 260 and the console noted coolant issues.

I checked and the electric fan is work. When the A/C is on, it comes on. And when the A/C is off, the fan is off until the temp hits a certain level then it kicks in. So this seems to tell me that the relay is working. And, the coolant levels are fine.

However regardless as to when the fan is on, it seems to be slow. Are these fans multi speed depending upon the demand or 1 speed. I'm trying to determine if the fan motor is shot (you can see some sparks from the fan motor when it is running and the engine compartment is dark).

Any suggestions/thoughts would be appreciative.
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Old 08-27-2010, 11:17 AM
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Re: Engine Coolant Fan

As far as i know the fan relay is not just a simple relay, but a pulse width modulated relay. The PCM can regulate the fan speed depending on the demand. But your car has the viscous driven fan on the waterpump pulley and the electrical fan behind the radiator, isn't it? The viscous driven fan turns normally when the engine is on and hot?
If the electrical fan turns slowly, it can be that your pulse width modulated relay has a problem.
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Old 08-27-2010, 11:58 AM
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Re: Engine Coolant Fan

Quote:
Originally Posted by Frango100 View Post
As far as i know the fan relay is not just a simple relay, but a pulse width modulated relay. The PCM can regulate the fan speed depending on the demand. But your car has the viscous driven fan on the waterpump pulley and the electrical fan behind the radiator, isn't it? The viscous driven fan turns normally when the engine is on and hot?
If the electrical fan turns slowly, it can be that your pulse width modulated relay has a problem.
This car doesn't have a mechanical fan run off the water pump....just the electric fan.

Is the pulse width modulated relay the one that is well hidden in the passenger side fender? I've had to replace that one awhile ago (what a pain) as the fan didn't come on at all then. This time, the fan is coming on just not screaming fast. Now don't get me wrong....it isn't turning so slow that you can see the blades...but it isn't turning fast that it's making a roar either. And last night while testing it, the temp was around 230 and not blowing any harder than it was at 190ish.
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Old 08-27-2010, 12:42 PM
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Re: Engine Coolant Fan

Yes, there is only one relay as far as i know and that one is nicely hidden underneath the RH headlight assy. Some guys overhere cut a hole in the plastic under the headlight to change the relay, just to not remove the whole bumper.
They just put it back in place with some glue i believe.
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