Testing your blower motor resistor - updated info

[bull]

This is on a 68 but I would imagine they're all pretty much the same. Check your schematics to make sure.

It's very simple if you have an ohm selection on your volt meter and even the most rinky-dink meters usually do. Dial meters are a little harder to read but you can still get a good idea. Reference the drawing below to know which lead wire goes to which terminal during the test. I've yet to find what the resistance values are supposed to be but here's what I got:

Low - 7.4 ohms
Medium - 2.3 ohms
High - .3 ohms

Results will probably vary some but as long as the low speed terminal gives you the highest resistance and the resistance readings progressively go down from medium speed and then to high speed you most likely can assume the resistor works.

Hook your positive lead to the lone terminal at the bottom of the drawing (where the motor plugs in) and leave it there during the test. Then attach the negative lead to the remaining three terminals one at a time to get your results.

Enjoy!

[Nacho-RT74]

not sure on 2nd gens, but on 3rd gens with A/C system, high speed DOESN'T GET the resistor. Goes directly from switch. Then BROWN is heater speed what is a diff one than A/C speeds.

Light green is medium and dark green is the output from resistor block to blower. Dark Green wire splices in to same dark green coming from control switch.

Tan wire is Low A/C speed

The deafult speed when turning on on 3rd gens with A/C is LOW speed.

I can explian detailed with graphics if needed.

Not to highjack, just to give more info

[bull]

not sure on 2nd gens, but on 3rd gens with A/C system, high speed DOESN'T GET the resistor. Goes directly from switch. Then BROWN is heater speed what is a diff one than A/C speeds.

Light green is medium and dark green is the output from resistor block to blower. Dark Green wire splices in to same dark green coming from control switch.

Tan wire is Low A/C speed

The deafult speed when turning on on 3rd gens with A/C is LOW speed.

I can explian detailed with graphics if needed.

Not to highjack, just to give more info

You're probably right. The high setting on the 68 doesn't really need to go through the resistor since the resistance is next to nothing but they do it anyway. I guess if nothing else it creates an added layer of protection for that circuit. If the circuit or motor shorts out that resistor will probably get too hot and burn out (melt) then in essence it will act a fuse. Assuming it would melt before the wiring.

[2Gunz]

The drawing seems to indicate that...........

The High speed is a direct copper bar connection. (no resistor)
The Med speed is a single resistor.
And the low speed is actually The med speed resistor AND one other resistor.

Mostly irrelevant, but at some point might help somebody with some sort of crazy problem.

Great post Bull!

[bull]

I found another resistor in a '63 Fury II wagon yesterday. It's visually identical to the one in my '68 Charger and two of the ohm measurements are pretty much the same but when I tested the low setting I found a large discrepancy.

'68 Charger resistor
Low: 7.4 ohms
Medium: 2.3 ohms
High: .3 ohms

'63 Fury wagon resistor
Low: 4.3 ohms
Medium: 2.5 ohms
High: .2 ohms

So basically the low setting with the original Charger resistor is really low compared to the Fury. Now I wonder if they are the same resistor and one is off or if they actually changed the settings to create more low speed resistance between '63 and '68. The resistors have different number stampings but other than that they are identical down to the color, shape and size. I guess I'll have to try them both later and see which one I prefer. The good thing about these resistors is they are very easy to get to.

Can anyone else check theirs to make a comparison? Maybe someone with a first gen.?

[John_Kunkel]

You're probably right. The high setting on the 68 doesn't really need to go through the resistor since the resistance is next to nothing but they do it anyway.

In an attempt to get more fan speed out of my '70 Charger blower I wired it directly to battery power. The fan speed increased noticeably but the motor overheated big time.