i am having some problem with blowing fuses on the heater motor, now it is just not as easy as a bad wire or replace the fuse, it has gremlins. The first time it blew the truck was fully warm and traveling when all of a sudden the heater went out, stopped had dinner and replaced fuse and had heat again for two weeks. the next time the fuse blew up on start up on a cold day, replaced the fuse and it still would not work. two days later it decides to start up, it blew three days later on start up in the cold. last time it blew while in travel when the truck was warm and had been heating for about 1 hour.

i have checked the wires, the motor seems to run freely,and had increased the fuse to a 35 amp. any suggestions?? please help.
tia, shawn

 

i am having some problem with blowing fuses on the heater motor, now it is just not as easy as a bad wire or replace the fuse, it has gremlins. The first time it blew the truck was fully warm and traveling when all of a sudden the heater went out, stopped had dinner and replaced fuse and had heat again for two weeks. the next time the fuse blew up on start up on a cold day, replaced the fuse and it still would not work. two days later it decides to start up, it blew three days later on start up in the cold. last time it blew while in travel when the truck was warm and had been heating for about 1 hour.

i have checked the wires, the motor seems to run freely,and had increased the fuse to a 35 amp. any suggestions?? please help.
tia, shawn

 

I think you need a new motor. Often electric motors will fail then run again for a while and then fail. It is trying to tell you something. I would highly recommend never going to a larger fuse to solve an electrical problem. The wires are designed a certain amperage and the fuse is there to blow if there is more than this to keep the wires from melting, protecting components in the system and to prevent fires.

 

Dap,
Change that motor before you have to change the wiring harness.
KingFisher

 

Please .....replace the motor right away before it causes a fire.

It is seizing up and is drawing too much current causing the fuses to blow.

 

since you all are telling me to change the thing how is the easiest way to do this? what time is involved? tia

 

Fuses are used as a sacrificial link in your electrical system and should not be replaced with fuses of higher amperage rating without accepting the fact that you are causing FURTHER damage. If you own a multimeter, take a resistance reading (ohm/Mohm) across the motor armature coil. Unless you can find the proper documentation you will need to measure a similar blower motor in order to compare your readings. In all reality a megger would be preferential since it will test the insulating quality of this circuit, however ENSURE that you never megger a circuit containing electronics. Since you are experiencing high currents within a somewhat fixed voltage system your only culprit could be LOWERED resistance (i.e. the blower motor winding varnish is impaired and the windings have shorted together => reducing the rating and performance of the motor; or somewhere there is a short in a connection or wire). Since you have been operating with a higher current fuse you need to inspect all wiring again thoroughly since the high currents cause high temperatures and will destroy electrical components. You stated that the fan turns freely so that would seem to eliminate mechanical binding, however I have repaired many DC motors that had merely come apart internally. My advice is to measure the old blower and determine if it is the culprit (with what I have heard I believe you should replace it). As an electrician in the Navy and now in a steel mill I have often seen the sad outcome of forcing a piece of machinery to work. Feel free to contact me for further clarification. Whatever the problem I am sure you will ELIMINATE it!

 

assuming that you have a non air truck here we go....take the vent off of the heater box (the one that flips up & down under the glovebox)..it's like 8 screws...then unhook the 3 prong wiring plug & control cable right beside the vent also..(take note of cable adjustment you need to put it back exactly where it is )..there is one more cable on the heater box that has to be removed too..it's toward the drivers side of the plug & 1st cable i mentioned....you might have to wait to unhook it untill you get the box loose from the firewall..(depending)...unhook the hotwire from the heater motor under the hood & remove the ground wire from the firewall...take the hoses off of the core (might wanna drain antifreeze first or it'll get messy fast)..next...just above & below the heater motor sticking out of the firewall there are 2 studs with nuts on them...remove the nuts...also directly behind the carb there's another stud..remove that nut too.. now just go inside the cab & wiggle the box out from under the dash (might take a while & dont forget the 2nd cable if you couldnt get it before)be careful not to bang the heater core inlet & outlet too hard on nything unless you plan on replacing it(might as well...they're only $20-$30)...once you get the box out from under the dash it's self explanatory from there....the 1st time i changed one it took me about an hour & a half...there's a knack to wiggling the box in & out...hope this helps...Chris

 

i agree 100% with hardworkinford about increasing the fuse size. dont do it!