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Blowing Blower Motor Fuses

12K views 7 replies 5 participants last post by  Frango100 
#1 ·
I have a 1999 Grand Cherokee and have had lots of electrical problems. I've replaced the blower motor resistor 3 times. This time the blower motor fuse (40 amp) blows as soon as current is applied. I took the motor out and it works good when I apply 12 volts to it. I spent hours working on this and it's very frustrating. This should have been a recall item, because it is a common problem with jeeps. Any help would be appreciated!!!
 
#4 · (Edited)
You talk about resistor, so you have the manual temp control system, right?
Did you check the connector from the blower motor that it is not melted? If that is ok, you need to check the wire bundle going from the power distribution center towards the cabin. Maybe the blower motor wire is shaved through at some place and causing the short.
And blowing the 40Amp fuse is not that common, at least i have never heard about it.
The wire from the PDC to the blower motor is a dark green one going from connector C1 on the PDC.
 
#5 ·
The motor will work when you apply 12v of direct current...thats why the fan works on speed 4 and not on the other speeds when installed. The problem I had with my motor was that in time the motor wears out and eventually it will begin to draw too much amperage. Thats why resistors fry and wires melt. Check the wire harness that goes into the resistor like the guy above mentioned. its very common to have to replace the harness when you replace the old resistor.If you continue to just replace the resistor pack you will find that it will keep going bad. I believe you just need to replace the blower motor itself...i got mine from rockauto.com.
 
#6 ·
If you're blowing a 40A fuse, then you have a short somewhere. I would start by measuring the resistance from the fuse to ground. It should have some resistance (say somewhere in the 10-30 ohm range). If it's a short circuit (or very close to it), then you need to figure out what's causing that. The other option is that it's NOT shorted, but still blowing the fuse. In that case, it pretty much has to be the blower motor is bad.
 
#7 · (Edited)
With the blowermotor connector removed, measuring from the PDC fuse, the resistance should be infinite. Most probably its not at this moment, otherwise the fuse would not blow. What i said before about connector C1 on the PDC, that was a mistake, C1 has to do with the wire identification number and not a connector.
 
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