96 HR Endeavor, Freightliner chassis, power wire suppling 12 v. for selector switch (dash AC and heat and fan) got so hot it melted fuse box connection. replaced wire and fan several times (new) still same problem. direct wire 12 v feed lets fan run without heating wire.When the selector switch is turned on the wires gets hot quick. (with 12v supplied to fan with seperate wire.)Any ideas, didnt find any bare wire grounding out or loose connections, I think the switch could be bad so Ill order a new one to try.:h

It's very likely that you have a bad blower motor.

have installed 3 new from Autozone and 1 new from NAPA its a standard Chevy blower motor.

I assume that the fan switch is multi-speed. I would guess that the resister element in the speed switch has a partial short to ground. You can use a multimeter to check the current(Amps) draw of your fan but I would guess that it is drawing a lot more current when hooked up through the switch than when wired direct. If it does, this would indicate a bad switch.

sch911when powered with a line from battery it runs fine and does not get hot. when the selector switch is moved to any position other than off the wire gets hot quick. turn the selector off and it gets room temp.

Blower Motor power wire getting very HOT | Good Sam Community

18 Replies

fourmat
Explorer
Jul 13, 2015
are you sure you don't have wires reversed on Motor?
CA_Traveler
Explorer III
Jul 13, 2015
Melted fuse box connections is a big red flag that it was bad - bad connections cause heat. Before getting as hot as you're experiencing the fuse should blow - why didn't it? Larger motor or larger fuse?

What is the voltage at the motor when running? The difference between the motor and batteries means power and heat are going somewhere. Everything is suspect, lug crimps, wires everything. A voltmeter is your friend to find the problems.
Jay58
Explorer
Jul 13, 2015
Agreed. Thanks... i ran power around the switch and the fan ran well without heating the wire. Also noticed that the compressor didnt kick in....another indicator the factory switch is bad.
jwmII
Explorer
Jul 13, 2015
Obtain a heavy duty switch. Install that and go up one size on your wiring. Keep the same size fusing as you have now. The present switch probably has burned contacts upping the resistance and causing the heat. It is not going to get any better. You may still have the Ford factory wiring but rest assured their engineering did not allow for anything extra in the way of current and heat.
Gau_8
Explorer
Jul 12, 2015
Resistance creates heat. The fuse box connections are probably compromised. You could use the factory connection to trigger a relay carrying the load.
Jay58
Explorer
Jul 12, 2015
I will order a replacement AC/Heater switch and inspect the resistor pack and spend more time tracing and marking the dash wiring before I reinstall the tv and dash section which I have removed to allow easier inspection.

I appreciate all responses and will update this thread as I learn more.
Jay58
Explorer
Jul 12, 2015
the fuse box i referenced earlier is the automotive bakelite box with fuses..(in the dash accessable from an access panel on the drivers side on top of the dash)...the wire supplying the ac selector switch was a wire plugged into it. (this is the original burnt wire / melted wire at the fusebox. I havnt located a fuse for this line yet. I trimmed it off and used the accessory and ignition power sources at a different location in an attempt to repower the AC.

I know this all sounds confusing,, as it is to me but Im not giving up.I can get there from here. I think it is called trial and error,
Jay58
Explorer
Jul 12, 2015
wires are factory original...my test power lead is 10ga,
rgatijnet1
Explorer III
Jul 12, 2015
The wire could also be too small for the fuse that is protecting it, which will allow it to get hot without blowing the fuse.
Jay58
Explorer
Jul 12, 2015
point taken.....I will check for the fuse I havnt found yet.