Heater resistor?

-
F

fireguyfire

Well-Known Member
Joined
Nov 27, 2023
Messages
95
Reaction score
68
Location
Alberta Canada
I’m troubleshooting a few small electrical issues with my newly purchased 67 barracuda.
One of the last issues is that the heater blower isn’t working. I pulled the heater box when I bought the car (it had a big mouse nest in it) and put all new gaskets, etc in the box. While out I put power to the blower motor itself and it ran nicely with the squirrel cage on it.
Now that it’s back in the car, when I turn on the fan switch I get nothing.
I got under the dash with my power tester and I confirmed that I have keyed power to the switch (black wire) and when the switch is on low I have power in 1 wire to the resistor, and if I turn it on high I have power to the resistor in the other wire (green and brown to the resistor).
So I’m pretty sure my issue is the heater resistor; is there a way I can test it to make sure it’s the resistor?
Are resistors available out there or are they tough to find?
 
Its the resister . I am sure someone near you will have a used one. I have them but shipping out of country is probably more then its worth.
 
You can temporarily bypass the resister.

But if the fan does not work in low or high I doubt the resister is the issue

There is a long ground wire that runs over to the right kick panel area. Without it and some other grounds you are not going to have a fan.

Also is there any draw on the system (ammeter) when the switch is turned firm off to low ot high?

Lastly you have the ignition key in the run or acc position when testing, correct?
 
The fan should at least work on "hi" with a bad resistor. Sounds more like the switch. You must test for voltage under a load, AKA with motor connected
 
I have never tried to weld or repair resistor (nichrome) wire but am sure it could be done. Also you should be able to figure out a "redneck" mechanical repair to clamp the broken resistor together. Have you looked at it? It is all open, coiled resistor wire. Very accessible
 
No draw with the fan switch turned off, and yes I’m testing with the key in the run position.
The ground sounds like a possible culprit; how does the blower motor and resistor ground? Is there an easy way to put a jump lead to ground and see if that solves the issue, and if so where should I connect the ground lead to the resistor
 
fireguyfire said:
No draw with the fan switch turned off, and yes I’m testing with the key in the run position.
The ground sounds like a possible culprit; how does the blower motor and resistor ground? Is there an easy way to put a jump lead to ground and see if that solves the issue, and if so where should I connect the ground lead to the resistor
Click to expand...
Resistor does not ground. It is in series with the motor hot lead. The motor (as I recall) should have a brown lead with an eyelet that wanders around somewhere in there. Look around up by the antenna, under the pass side cowl vent can, etc.
 
I’ll pull the glovebox liner so I can have better access to the resistor etc for testing.
Dumb question here fellas but for the sake of learning, what exactly does the heater resistor do?
I’m assuming the 2 wires in the resistor have different resistance to deliver “low” and “high” speed power to the fan motor?
 
Last edited:
fireguyfire said:
... what exactly does the heater resistor do?
Click to expand...
The heater resistor is what gives you your fan speeds.
No resistor, straight from the switch is High.
Then two resistors (one with a tap, actually, if I'm not mistaken), each fed by a different wire from the switch for Med and Low.

More resistance = less speed.

The resistors get hot, as they are fairly low resistance and the motor draws a decent amount of current, so they are placed in the air stream of the blower, to keep cool.
However, over many years and miles, usually they're not kept quite cool enough, and something melts, and *POOF!* no more Med and Low.

They used to be a dime a dozen at every auto parts store, not sure now, but any heater resistor from any car ever made can probably be adapted, and ones with resistance close to the original should work identically (otherwise your Med and Low could run a bit faster or slower than you want).

As stated above, if you don't have High, then the problem isn't your resistor, so check grounds - just jumper a metal part of the motor to a clean metal part of the car and see if it works.

– Eric
 
Also, testing, the heater resistor is designed to be mounted in the duct so that the fan cools it. Do not run it for long in free air, as you may burn it up. Watch it for "red"
 
Just went through all of the above with my RR. First, I had a bad ground because of paint. Second, I had no high speed. In my case, it's the switch. I opened it up and cleaned the contacts. I still have a high speed issue, but can get it to work in-between med and high, most times. But, you have power it seems, trace down your ground, then maybe the resister.
 
You must log in or register to reply here.
-

Back
Top