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86 4.9 4spd std. There's no power to my blower switch on any speed. I remember seeing something on this forum a few years ago about some little electric thing that was behind the glove box area.. does anyone know what I'm referring to. Any help is appreciated...right now I tapped into it from battery to a aftermarket switch that's floating under the dash...but now I'm bring this truck back to a daily driver standards
Last edited by James Heathcoat; Aug 25, 2025 at 06:48 PM.
Reason: Remove pole option
Blower motor resistor. You can buy the one for AC, it was like $26. years back. Here's the 1975 Jeep one I got for $6.00 about 10 years back, when all I could find was the one for AC.
I thought the blower would always work on High, even with a bad resistor. I had high speed, but not the lower speeds.
Yes that dohicky is in the engine bay on the HVAC box like Max shows just a little different being you have factory? AC.fan switch and the other end
I also thought the fan would work on high only if bad but .......... on my 02 Durango the fan would stop working at times because the resister was bad / plug melted.
Also the factory AC is a add on harness for the blower IIRC
The trucks harness unplugs from the fan switch and this add on harness plugs into the switch and the trucks harness.
Cant remember what else it had as its been 6+ years since I had the harnesses out for the rebuild.
I think I would take a test light to the plug for the resister and see if you have power there and then back trace till you get power.
You did check the fuse as I think there is a fuse for the fan.
Let us know what you find as it may help others.
Dave ----
The resistor pack is completely bypassed with the fan switch in HI. It is only used for the 3 lower speeds. You could completely remove it and the fan should still operate with the switch set to HI. Don't get sidetracked chasing the resistor pack, at least for now.
Check fuse #9. It's a 30 amp fuse that feeds the fan and the AC clutch circuit. Does your AC work, or at least does the compressor clutch engage? If so, that would tell you the fuse is good.
After that, you're going to have to poke around with a test light (preferred) or voltmeter to wring out the circuit and find the fault. It's possible there's a wiring fault, but more likely a switch has failed. The power supply side of the circuit passes through the ignition switch and the mode selector switch (AC, Vent, Floor, etc.) before reaching the fan motor. The ground side of the fan is not constant, but goes through the fan speed switch. Leave the speed switch in HI for your initial troubleshooting.
In the wiring diagrams, see page 151 for testing the mode selector switch. The fan speed switch is covered on page 152. You can test the ignition switch here in a matter of minutes with easy access via the fuse panel:
Where to start? I'd suggest connecting everything as normal. You will find two wires on the blower motor, orange and black. The orange is the switched power supply. Black is the switched ground. Turn the key to Run. Fan switch to Hi. Mode selector to any function except Off. With the connector still installed, backprobe the plug with your meter's test lead. If the lead won't fit, use a paper clip or similar as an extension. You should have full battery voltage on the orange wire. If not, you've got a problem upstream of the fan. If good, change your meter to resistance and you should have good continuity between the black wire and the battery's negative terminal. If not, the problem is on the ground side of the fan circuit, probably the fan speed switch.
right now I tapped into it from battery to a aftermarket switch that's floating under the dash...
To help with troubleshooting: Can you please elaborate how this switch is connected to the fan motor?
See my previous comment about how there are two switches in series on the power supply to the fan, and then a third switch on the ground side. All three have to work to power the fan. I'm guessing your new switch bypasses the ignition switch and the mode selector switch. Is that correct?
What about the black ground wire on the fan? Is that still connected? If so, that means the fan speed switch is working, at least to some extent. Or did you simply run a new direct ground and bypass that switch?
Yes...truck has AC ...it's effecting all blower functions...I remember seeing something about a part located behind the glove box
I have an '81 with AC and I had the whole dash out this spring, replacing vacuum lines and I dont recall *anything* electrical behind the glovebox. Wires run through that area but no relays or anything of that sort in that area.
I also had my 81 F1oo with AC apart years ago and you are right there is nothing for the blower motor back there only the seat belt / head light buzzer.
If you looked close enough you would have seen there was an adapter harness added when factory AC is added but as I said in my above post.
The only thing that could keep the fan from working is a bad fan, bad wiring or bad resister, oh bad switch too.
Dave ----
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