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Unread 07-02-2010, 05:28 PM   #1
Zamboni0neXJ
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1999 XJ Cherokee 
 
Join Date: Jan 2010
Location: St Cloud, MN
Posts: 21
thermal fuse, blower motor and fan controller woes

I have replaced everything mentioned above and some twice. Something is making the load on the thermal resistor enough to make it fail and go into the high only setting. On top of that, the controller, under heavy load (ac mainly) shuts off and on every 4 seconds. Blower motor is brand new, thermal resistor was brand new. Replace the controller unit and the plug on the drivers side. Plug was melted and damaged. Haven't taken it apart to see if it got nuked yet.

Please send any and all ideas my way. I am brain shot now.

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Unread 07-02-2010, 09:19 PM   #2
BrunoS
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sounds like case of high voltage under the hood.

1) what year xj is this?

2) what is the engine running battery voltage?

3) common failure part in 96 and older xj was the blower speed switch, which got dirty/hot spots/failed at the wiring harness connector (would smell like melted plastic at the dash when the blower was on hi speed).

4) if that speed switch connector is fried (like mine was) then you may have a short at that point which is causing your problems;

5) or your alternator is overcharging (like 16 volts or more) and this is yet another thread.
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Unread 07-03-2010, 09:19 AM   #3
Zamboni0neXJ
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I forgot to fill out my profile sorry. Its a 99 sport.

Voltage has been normal. I did smell what seemed to be an odd smell after replacing the controller. I am leaning towards it being a bad controller, but never thought about a short. Thanks, I will begin my painful search.
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Unread 07-03-2010, 09:42 AM   #4
myriad360
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2001 XJ Cherokee 
 
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Check the fuse values in your fuse box if this circuit is included, something is running hotter than it should. X 2 above, if the fuses are correct, you probably have a short somewhere. Ammeter?
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Unread 07-04-2010, 07:53 AM   #5
Zamboni0neXJ
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I think I tracked the short down. It was in the blower motor itself. Resistor was still good. Swapped out blower motor and no problems so far.
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Unread 07-04-2010, 01:31 PM   #6
myriad360
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Quote:
Originally Posted by Zamboni0neXJ View Post
I think I tracked the short down. It was in the blower motor itself. Resistor was still good. Swapped out blower motor and no problems so far.
Didn't you already replace the blower motor?
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2001 Jeep Cherokee 4.0 L Limited, White. Bought in Grangeville, ID 06/11/08. Stock everything.
1998 Jeep Wrangle 4.0 L, Green. Bought in Nampa, ID 02/21/09
1988 Jeep Cherokee 4.0 L, White. Bought in Vancouver, WA in 2003. 1st Jeep, White. Bought with 3" lift, added Pacesetter header and 40 series Flowmaster
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Unread 07-04-2010, 06:27 PM   #7
Whackmaster
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I was having the same problem with my 99...After replacing the blower motor twice it worked fine for about 3 months but it is back to the old way...I have given up............
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