Question about 2003 Jeep Grand Cherokee

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Fan replacement The fan doesn't work. Replaced the fan motor today and still not working. Could it be a problem with the relay switch which, I believe, is under the passenger side head lamp assembly.

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  • chrisdean7 Aug 22, 2008

    I have a 2003 jeep grand cherokee.  The radiator cooling fan motor will not come on.  Did check continuity in motor and it was good. (if this means anything are not?)  But i am wondering if changing out the relay would be a good start and if so is it that difficult to change the fan relay if you have some mechanical skills? Thanks, Chris

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My answer:

I answered a similar ? at Yahoo Answers awhile back, and it solved that person's problem on their 1987 Jeep.

Though you weren't very specific as to your 2003 Jeep Grand Cherokee's problem by just saying the fan motor doesn't work, I'm taking it that we are talking about the "radiator fan motor" here.

You most likely have a two-fold problem going on with your radiator cooling fan.

Seeings a new fan motor didn't solve the original non-op problem we can definitely establish that the old fan being bad really wasn't bad at all and NOT the problem to start with.

As with any 12-volt DC automotive motor (whether for the radiator cooling fan, windshield wiper motor, interior passenger compartment cooling/circ fan, etc) a simple disconnected from the car's electrical system test should have been done 1st to make sure the old fan motor was really bad. Too late for that now though. I myself would have seriously doubted that a 6 year old fan motor would have been bad already.

If you had no recent engine or radiator related mechanical work done to the Jeep - as of late - then the problem may not even be a bad wiring harness connection, but you never know.

If all the radiator fan Temp related Sensors & Thermal Switch connectors are properly seated then we need to look at yet another possibility having eliminating a wiring connector type problem.

On most radiators with an electric assist fan(s) there is also an electric Thermo Sense switch (TS) mounted on the radiator itself that has to be working properly otherwise this fan switch could stick in the CLOSED position (set point usually 190 degrees F) leaving the fan to run all the time while the engine is running. Make sure it is connected as to the wiring connector, as I've seen this connection get pulled apart from other engine related work being done or else from a bad connector itself.

If this TS goes bad and someone disconnects it so as to stop the fan from running all the time - then it may look like the fan itself is bad when it really isn't.

On the other hand this TS switch could actually stick in the OPEN position (though this is very rare with this type of Thermal switch), and then the fan wouldn't run at all, and the engine would probably run HOTTER then normal as a dead giveaway. If your engine is running HOTTER then normal I would go directly to this TS and check it for proper operation. It's usually mounted on the radiator fan bracket nearest the radiator with a separate 2-wire wiring connector.

If it's working properly - when the ignition is turned off - the fan should still turn off as it is usually controlled by a timed RELAY circuit as a failsafe. Does it??

Hopefully you don't have any engine cooling problems to start with, but if you do follow the guidelines below:

If the engine thermostat is sticking CLOSED, or indeed stuck CLOSED, that could also cause the fan to run excessively. Running plain water in the engine and not proper 50/50 antifreeze/coolant mix can also cause the engine to run much hotter then normal and thus adds to running the radiator fan more frequently then normal.

Excessive radiator fan running leads to just one thing, and that is worn out bearings. Some of these fans aren't made that good to begin with!

If the fan is indeed 'tired' or has a tendency to try and freeze up there should be safeguards to prevent wiring from burning up.

Most radiators have 2 thermo-switches (TS), one being an ambient radiator surface mounted TS, and the other one being an internal (screwed into) radiator mounted TS. There might even be a 3rd fan TS that is clipped directly to the fan motor case itself to sense an over-temp situation like that from the fan bearings freezing and the fan itself running hotter then normal. Just depends on car maker design.

There is also a TIMER RELAY module incorporated in all CA equipped cars as part of the SMOG packaging for cars sold here in this state. Reason for that is to reset the pre-warm circuit properly when restarting the car back up after shorter run and stop trips. If this relay is bad it could cause the fan to run on longer then normal after shutting off the vehicle, thus causing undue wear and tear on the fan motor also. I used to think it also helped to clear out any fuel fumes from under the hood after running the engine, but could never prove it or have it verified by own my minivan maker when I owned a minivan??

NEVER DRIVE THE JEEP WITHOUT THE FAN MOTOR BEING CONNECTED!! You will surely damage something you don't want to!!!

To check the radiator fan circuit do the following:

I would first disconnect the battery from the circuit, and do any resistive type DVM meter checks first (unless you are unsure of how to do them), and then do the following checks below to check out the fan motor and related sensors/switches with power reconnected. If you have a lot of MEMORY type devices onboard your Jeep (Stereo, GPS, etc) you might want to use a simple 12-volt TEST LIGHT or again a good DVM to trace for a good ~12-volt battery voltage at point-to-point connectors instead, so as not to lose those memory settings.

First check the wiring leading to and from the fan motor itself and the TS (1 or possibly 2) connectors to make sure they are snapped together fully and making good connections. Also check the GROUND WIRE coming off the fan motor connector - as if this ground point is dirty or corroded causing a bad ground return path then the fan motor will appear to be dead as well.

Next check the fan itself for free-play. Is it turning freely or is it very tight or hard to spin?? If so - you have a bad fan and it's time to replace it NOW! (In your case it doesn't appear to be a bad fad fan motor at all.)

If you are handy with a digital volt meter (DVM) connect it in DC series with the fan motor and while running the Jeep measure the current and compare it to a new fan's rating. If it's excessive then the fan motor is on it's way out. Time to replace. (Skip this part too, as your fan is known good.)

VERY IMPORTANT STEP HERE - Also check those 1 or 2 TS switches to make sure they are in the OPEN setting with a COLD engine/radiator. CHECK AGAIN to make sure they CLOSE at the proper engine temp as well. If they don't close at or near 190 degrees F then one or the other (if there are 2 or more in your system) may be bad, and that may very well be your only problem.

If Jeep has added a FUSE or FUSIBLE LINK to the fan circuit make sure you check that part also. It's doubtful though, as the fan circuit is fairly simple by design. A Timer Relay type Switch would be downstream of the/any TS switch(es) by design as well, so I would place my money 1st on a bad TS switch, or a possible bad ground connection 2nd.

Does not appear to be anything else that excessive as it looks to just be isolated to the radiator fan circuit itself.

Hope this helps you out to troubleshoot the problem. Feel free to email me if you still have further ??'s.

Frank

Posted on Aug 10, 2008

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