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Wiring problem, Inop heater blower

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Chasing down a wiring gremlin in my '89 MJ 2.5L, trying to diagnose an inoperable heater blower. I've had the blower motor out and it works fine when 12v is applied. Here's my ref material: http://www.bteventures.com//mj1988electricalmanual.pdf


I tested the positive lead to the blower at the blower and it showed around .7v and I tested the ground at the same location and it seemed fine. I jumped straight to the fuse panel beneath the dash and tested the blower feed. .7v at this location as well. I tested the two other items on the same circuit and the radio feed tested at .7v and the turn/BU feed tested fine at 12.5v.


Any ideas as to why I'd have 2 different voltages between the 3 items on the same circuit?


I'm not very experienced diagnosing electrical problems so all help would be greatly appreciated.

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Alright stupid question but ive experienced it....


Have you had the CD player out or replaced it with another? Check the plug behind the controls if you have, i knocked mine loose 1 time and couldent for the life of me figure out why the blower motor wouldent run.


If thats not the case check the resistor above the passengers feet under the dash. :thumbsup:

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Mine quit working as well last year. It wound up being the corrosion and years of brake fluid seapage on the fuse block and years of overheating and blowing fuses. The fuse simply will not make good contact in the right slot. For now I've got it jumped to another 25 amp spot on the FB. Problem is I have to turn it off every time I park the truck. I'll have to find a better solution. I'm been to busy to try and repair the fuse block. I will probably bypass the FB because it might be deformed just enough not to be able to repair. Anybody add new contacts to a fuse block? I want to say I've seen the correct brass connectors before.


To answer your question-yes I took mine apart to spray it with electronics cleaner. A good idea given the common problem with the leaking clutch master.

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