Low coolant light
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Joined: Jun 2009
Posts: 13,966
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From: Fort Worth, Texas
Re: Low coolant light
Originally Posted by X-fired
My Low Coolant Light has been coming on as well AND my A/C has been intermittent.
I ran some tests as described above and it appears that my fan is dead. I'm hoping that the funky A/C operation is due to the fan not functioning too. i.e., if the fan runs when the A/C is no, maybe the A/C doesn't run when the fan is not running.
Getting new fan. Will report back.
I ran some tests as described above and it appears that my fan is dead. I'm hoping that the funky A/C operation is due to the fan not functioning too. i.e., if the fan runs when the A/C is no, maybe the A/C doesn't run when the fan is not running.
Getting new fan. Will report back.
Joined: Jul 2010
Posts: 5
Likes: 1
Re: Low coolant light
Alrighty then, I had the chance to tinker with the trouble shooting. I tested the fan to see if it was working by jumping it, the fan runs when jumped. I checked the 50 amp fuse, it was blown, I replaced it with a new one from the dealer for only $4.20 . Light went off for 5 minutes then turned right back on, I had a sneakie suspicion to check the fuse again and it was blown again.
The Fan works when jumped but the fuse keeps blowing out, anyone have an idea? could it be the control module?
The Fan works when jumped but the fuse keeps blowing out, anyone have an idea? could it be the control module?
Originally Posted by pizzaguy
Now, wait. You replaced the fan MOTOR, right? If the motor is new and power it reaching it via the control module, then the new motor is bad.
Disconnect the fan motor harness from the rest of the harness - get some reasonably heavy wire, two pieces, and strip both ends. Jumper directly from the battery + and - posts to the two terminals of the fan motor and PROVE that motor is good. If it runs, I'd say your fan module is bad or a fuse is blown.
If ANYTHING else is wrong (say the ECM is not talking to the Fan Module) the Fan Module will go into "emergency mode" and turn the fan on full speed.
IF the fan motor refuses to run (and it runs at low speed whenEVER the A/C is on) - It has to be the fan motor, fan control module or fuse. There are no other options.
Disconnect the fan motor harness from the rest of the harness - get some reasonably heavy wire, two pieces, and strip both ends. Jumper directly from the battery + and - posts to the two terminals of the fan motor and PROVE that motor is good. If it runs, I'd say your fan module is bad or a fuse is blown.
If ANYTHING else is wrong (say the ECM is not talking to the Fan Module) the Fan Module will go into "emergency mode" and turn the fan on full speed.
IF the fan motor refuses to run (and it runs at low speed whenEVER the A/C is on) - It has to be the fan motor, fan control module or fuse. There are no other options.
Senior Member
Joined: Jan 2008
Posts: 5,180
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From: North Plains, OR
Re: Low coolant light
Is the fan running full bore with no squeals or sqawks??? It could be wobbeling and binding to cause the fuse to blow.... It should run at full speed(keep your fingers and loose clothing out of the way) when hooked directly to 12v... dont run it very long either.....
I dont think anyone has found that the control module was the REAL cause so far......
I dont think anyone has found that the control module was the REAL cause so far......
Joined: Jul 2010
Posts: 5
Likes: 1
Re: Low coolant light
Fan works just fine when jumped directly to the 12V using 2 heavy duty wires.
Originally Posted by MikeR
Is the fan running full bore with no squeals or sqawks??? It could be wobbeling and binding to cause the fuse to blow.... It should run at full speed(keep your fingers and loose clothing out of the way) when hooked directly to 12v... dont run it very long either.....
I dont think anyone has found that the control module was the REAL cause so far......
I dont think anyone has found that the control module was the REAL cause so far......
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Joined: Jun 2009
Posts: 13,966
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From: Fort Worth, Texas
Re: Low coolant light
It COULD be the module, but I have a problem believing that. The control module essentially has two main sections in it.
1) A microprocessor based "brain" that takes the pulses from the ECM and sends acknowledgment pulses back to the ECM. This is certainly a Large Scale Integration electronic assembly that simply could not sink 50 amps without certain damage. I just can't see it sinking that current.
2) A switching transistor arrangement driven by the section above that turns the fan on and off. (At times it wants to run the fan slowly, it turns the fan on for, say 50 milliseconds then off for, oh, say, 250 milliseconds and repeats this sequence over and over).
I suppose the switching transistor(s) COULD become leaky, it happens in electronic police sirens all the time.
TO test it:
Start with a cold engine. (You don't want to hurt the engine by playing around with this while the engine NEEDS cooling.) Put in a new fuse. Unplug the fan from the harness. Turn the A/C on (so the fan is commanded to run at slow speed) and start the engine. The module will light the low coolant light because it senses there is no current going to the fan - don't let that bother you.
Give it several minutes and see if the fuse blows. If it DOES blow, the module did it!
If not, plug in the fan.
IF the fuse NOW blows, the motor almost certainly has to be bad.
If it STILL won't blow again....................................... welcome to the world of electronic troubleshooting.
ONE LAST THING: I have GOT to get some stuff done around the house, so I can't take time now... but there IS a possibility that the fuse feeds other stuff in the car and THAT is what is blowing the fuse. Again, it takes time to go thru the diagrams in the service manual, can't do that right now. Maybe someone else here knows...
1) A microprocessor based "brain" that takes the pulses from the ECM and sends acknowledgment pulses back to the ECM. This is certainly a Large Scale Integration electronic assembly that simply could not sink 50 amps without certain damage. I just can't see it sinking that current.
2) A switching transistor arrangement driven by the section above that turns the fan on and off. (At times it wants to run the fan slowly, it turns the fan on for, say 50 milliseconds then off for, oh, say, 250 milliseconds and repeats this sequence over and over).
I suppose the switching transistor(s) COULD become leaky, it happens in electronic police sirens all the time.
TO test it:
Start with a cold engine. (You don't want to hurt the engine by playing around with this while the engine NEEDS cooling.) Put in a new fuse. Unplug the fan from the harness. Turn the A/C on (so the fan is commanded to run at slow speed) and start the engine. The module will light the low coolant light because it senses there is no current going to the fan - don't let that bother you.
Give it several minutes and see if the fuse blows. If it DOES blow, the module did it!
If not, plug in the fan.
IF the fuse NOW blows, the motor almost certainly has to be bad.
If it STILL won't blow again....................................... welcome to the world of electronic troubleshooting.
ONE LAST THING: I have GOT to get some stuff done around the house, so I can't take time now... but there IS a possibility that the fuse feeds other stuff in the car and THAT is what is blowing the fuse. Again, it takes time to go thru the diagrams in the service manual, can't do that right now. Maybe someone else here knows...
Last edited by pizzaguy; Sep 2, 2010 at 08:48 PM.
Joined: Jul 2010
Posts: 5
Likes: 1
Re: Low coolant light
Thank you, i'll try again on a free day.
Originally Posted by pizzaguy
It COULD be the module, but I have a problem believing that. The control module essentially has two main sections in it.
1) A microprocessor based "brain" that takes the pulses from the ECM and sends acknowledgment pulses back to the ECM. This is certainly a Large Scale Integration electronic assembly that simply could not sink 50 amps without certain damage. I just can't see it sinking that current.
2) A switching transistor arrangement driven by the section above that turns the fan on and off. (At times it wants to run the fan slowly, it turns the fan on for, say 50 milliseconds then off for, oh, say, 250 milliseconds and repeats this sequence over and over).
I suppose the switching transistor(s) COULD become leaky, it happens in electronic police sirens all the time.
TO test it:
Start with a cold engine. (You don't want to hurt the engine by playing around with this while the engine NEEDS cooling.) Put in a new fuse. Unplug the fan from the harness. Turn the A/C on (so the fan is commanded to run at slow speed) and start the engine. The module will light the low coolant light because it senses there is no current going to the fan - don't let that bother you.
Give it several minutes and see if the fuse blows. If it DOES blow, the module did it!
If not, plug in the fan.
IF the fuse NOW blows, the motor almost certainly has to be bad.
If it STILL won't blow again....................................... welcome to the world of electronic troubleshooting.
ONE LAST THING: I have GOT to get some stuff done around the house, so I can't take time now... but there IS a possibility that the fuse feeds other stuff in the car and THAT is what is blowing the fuse. Again, it takes time to go thru the diagrams in the service manual, can't do that right now. Maybe someone else here knows...
1) A microprocessor based "brain" that takes the pulses from the ECM and sends acknowledgment pulses back to the ECM. This is certainly a Large Scale Integration electronic assembly that simply could not sink 50 amps without certain damage. I just can't see it sinking that current.
2) A switching transistor arrangement driven by the section above that turns the fan on and off. (At times it wants to run the fan slowly, it turns the fan on for, say 50 milliseconds then off for, oh, say, 250 milliseconds and repeats this sequence over and over).
I suppose the switching transistor(s) COULD become leaky, it happens in electronic police sirens all the time.
TO test it:
Start with a cold engine. (You don't want to hurt the engine by playing around with this while the engine NEEDS cooling.) Put in a new fuse. Unplug the fan from the harness. Turn the A/C on (so the fan is commanded to run at slow speed) and start the engine. The module will light the low coolant light because it senses there is no current going to the fan - don't let that bother you.
Give it several minutes and see if the fuse blows. If it DOES blow, the module did it!
If not, plug in the fan.
IF the fuse NOW blows, the motor almost certainly has to be bad.
If it STILL won't blow again....................................... welcome to the world of electronic troubleshooting.
ONE LAST THING: I have GOT to get some stuff done around the house, so I can't take time now... but there IS a possibility that the fuse feeds other stuff in the car and THAT is what is blowing the fuse. Again, it takes time to go thru the diagrams in the service manual, can't do that right now. Maybe someone else here knows...
Joined: Jul 2003
Posts: 247
Likes: 3
Re: Low coolant light
This thread saved me a lot of work! My low coolant light and odd A/C operation were indeed caused by a dead engine cooling fan. I tested the fan by connecting it directly to the battery to confirm it had passed. I ordered a VDO fan from AutoZone for $195 which came in the next day. Installation took about six minutes.
All is mostly well. My cabin fan still shuts off occasionally but that's another story.
Cheers.
All is mostly well. My cabin fan still shuts off occasionally but that's another story.
Cheers.
Joined: Mar 2007
Posts: 22
Likes: 0
Re: Low coolant light
Had same problem, had wiring check etc. Had to order a new fan from Chrysler, it came from Germany so it took a week. Very easy to install, cost me $20 to have installed and $240 for the complete fan assembly. No problems since.
Joined: Feb 2017
Posts: 3
Likes: 0
From: Pompano Beach
Re: Low coolant light
Radiator cooling fan was getting very loud. Then a couple of weeks later it was turning off and on radomly. Then not working at all. Bought a new fan Dorman part number 620-040. Takes about 10 minutes to swap out. Still nothing. Then if you look at the pictures. Problem found. Need a new auxiliary relay controller
Last edited by Leecook; Mar 30, 2018 at 04:42 PM. Reason: Typo
Senior Member
Joined: Apr 2006
Posts: 25,432
Likes: 648
From: Ontario
Re: Low coolant light
Radiator cooling fan was getting very loud. Then a couple of weeks later it was turning off and on radomly. Then not working at all. Bought a new fan Dorman part number 620-040. Takes about 10 minutes to swap out. Still nothing. Then if you look at the pictures. Problem found. Need a new eggs is auxiliary relay controller
I’ll add this to the Index of Problems, but what is the last sentence, new eggs?
Senior Member
Joined: Dec 2010
Posts: 12,780
Likes: 184
From: Lineville, AL
Re: Low coolant light
Radiator cooling fan was getting very loud. Then a couple of weeks later it was turning off and on radomly. Then not working at all. Bought a new fan Dorman part number 620-040. Takes about 10 minutes to swap out. Still nothing. Then if you look at the pictures. Problem found. Need a new auxiliary relay controller
Senior Member
Joined: Apr 2006
Posts: 25,432
Likes: 648
From: Ontario
Re: Low coolant light
Any eggs should be chocolate, it is Easter after all.
ESG? You got me there, you and Padgett should get together and come up with a thread explaining these.
ESG? You got me there, you and Padgett should get together and come up with a thread explaining these.
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