About 30-40 seconds after I close the circuit on the blower switch [lo,med or high] it blows the 30 amp fuse. I connected a fused circuit directly to the blower motor and it ran without problems. I am looking for advise as to what else might cause this problem. The vehicle is a 1984 f150 4x4 with a
302. Thanks to all.If so, following the circuit to the crispy area will show the broke bit.
Dave
There are resistors in circuit that may be causing the problem, they control the motor speeds from what I have read here in the group from the past. Leaves sometime get caught near them also. They are supposed to be mounted in the air box so air passes over them to cool them.
Do a search of this group to find more information on blower resistors.
Blair
Try looking for/finding a ground @ the switch.
If a direct connection jumper wire works, why not put a switch in that ckt and effectively rewire it?
The post where the guy's been finding a high resistance in the fan circuit causing fuses blown is sure new to me, I'd like to know more details about that one. :) No kidding.
It really does sound like a true "short circuit" as opposed to most electrical problems cause by "opens or high resistance" doesn't it?
Trace the wires out. I had trouble with the windshield wiper (link between the two) sawing into the wiring harness and shorting out and ruining the accessory relay's contacts.
The resistance coils that lower the fan speed aren't in the circuit when the switch is on high (in all of the ones I've messed with) so I don't believe it's that. Unless that "coil block" is grounding out big time.
How does the fan sound at start up? Is there any indication of the fan bearings being tight or other friction? You might be over coming that with the straight wire.
If you ever take any used speed control switches apart I bet you'll find everyone of them with signs of the high speed contact getting really hot. That might be a clue to you and it might not. :/
Usually I jump in with "get a meter dammit" but with "true shorts" a meter won't find it for you so good but if you wanted to use one it could help.
Alvin in AZ
The leaves in the blower box actually caught fire before it blew the fuse on my '86.
Tom J
racin20 wrote
I had an E-250 that would blow a fusible link at night killing the headlights. Turned out the parking brake mechanism had chafed a wire next to it, and shorted when I stepped on the pedal. js
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