# [SOLVED] car heater blowing fuse 2003 jeep grand cherokee



## vncntsbr (Jun 9, 2009)

Hi 
ineed any suggestions out there.when i turn the ignition key to on the fuse for the heater/ac blows. I replaced the fuse. heater worked for 2 days then the fuse blew. now when I turn the ignition on the ac/ heater fuse blows immediately. the fuse blows when the heater/ac controls are off. I down loaded a fuse box diagram from wjjeep.com/fuses and it states that fuse # 20 10amp controls ignition run/ heater/ac,/left and right turn signal sense and heated seats. I do not have heated seats. what is ignition run and left and right turn signal sense? could one of these circuits be the one that is blowing the fuse? I disconnected the ac compressor and inside the engine I removed the 15amp fuse and a relay for the ac clutch and a 40 amp fuse for the blower motor the fuse still blows when I turn on the ignition with all heater controls off. I hope someone can help me with this problem


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## octaneman (May 13, 2009)

*Re: car heater blowing fuse 2003 jeep grand cherokee*

Hi vncntsbr


F20 on the diagram means that this particular fuse acts as a breaker for all the systems hooked into it. Ignition run means that fuse gives power to the run position on the key and the rest of the circuits. You have already isolated the circuit that blows the fuse because you disconnected everything else, in this case its either on the key or the flasher unit side. To find out which side is drawing the excess current, disconnect the flasher molex connector from the steering column, replace the fuse and turn the key on. If the fuse doesn't blow then the fault is in the flasher unit, if it does its on the key side. Use a test light to probe any short to ground problems, follow the wiring diagram and do a visual inspection make sure all grounds to the circuit you are testing are solid. 



post back your findings.


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## vncntsbr (Jun 9, 2009)

*Re: car heater blowing fuse 2003 jeep grand cherokee*

I found a short in a wire that was connected a senser connected to the oil pan of the transmission . By shifting the gears i noticed that the turn signal would work in park reverse and neutral and sometimes in drive. when the wire was shorted out the turn signal would work and the heater would blow a fuse. I fix the short in the wire reconnected it to the trans. the heater and the turn signal works fine. I still can't figure out why a wire connected to the trans. can cause the fuse for the heater to blow. if anyone has this problem check this wire it is located on the driver side of the trans. connected to the oil pan of the trans. the dealer wanted to charge $200-300 it cost me the price of a roll of tape


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## Basementgeek (Feb 7, 2005)

*Re: car heater blowing fuse 2003 jeep grand cherokee*

Hi:

Thanks for letting us know you got it fixed. I will mark this post as "Solved"

BG


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## psc777 (Jul 20, 2012)

Just wanted to say thanks for this. Friend does a live stream on Twitch from the repair shop, had an 04 Jeep in with a similar problem, pointed this out via the live chat, and sure enough! that was the problem! Saving possible hours in diagnosing, also passing the savings onto the customer!

https://www.twitch.tv/deamonmachine


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