Blower fan not working - is there a way to test the heater fan switch and confirm it's likely the blower motor?

[72Polara360]

1973 Dodge Polara factory non-A/C car.

So far I've removed the lower dash panel and traced wires from the switch to the resistor, everything seems okay and I removed and inspected the resistor and it almost looks new.

I am beginning to suspect the blower motor but I am wondering if there's a way to test switch function before I go removing the inner fender and looking at the blower. I did try to remove the switch but it's pretty firmly affixed to the dash, not sure how to get it out and bench test it, short of removing the whole dash. I undid two screws visible with the lower dash panel off but they just held the face plate in place. Further, the air dam selector knobs really don't want to come off their levers for some reason so I didn't even get the faceplate off. I could not see any screws that would have allowed me to pull the unit out.

Is there any way to test switch functionality with it installed? Or is it time to bite the bullet and replace the blower motor?

Picture of the resistor for fun.

 

[Ross Wooldridge]

Does the blower motor poke out into the engine bay, and is there a wire running to it? If so, that's the feed from the blower motor resistor. The motor grounds to the chassis, so if you put 12 volts directly to the wire (there should be a connector), then the motor should fire up if it's good.

 

[72Polara360]

I did see a wire going into the box in the passenger foot well but I didnt sight one in the engine bay. I'll have to have another look. The one going into the passenger foot well box didn't have a connector unfortunately.

By the way, in your signature is that the water works plant in Toronto?

 

[Ross Wooldridge]

Find the feed going directly into the blower motor.

Your nan switch may be bad too.

Yes - RC Harris Filtration plant in Toronto.

 

[Ross Wooldridge]

Pretty sure the green single wire on the blower resistor is what feeds the blower motor. Look at the wiring diagram to be sure.

 

[72Polara360]

Pretty sure the green single wire on the blower resistor is what feeds the blower motor. Look at the wiring diagram to be sure.

I'd recognize those water works anywhere, popular high school drinking spot in the east end back in my day haha.

Is this is the likely candidate wire? (Pictured red arrow) Seems to be the one, as it branches off from the rest of the harness. I will double check my wiring diagrams though, I have the chassis and the body manual hopefully it's in there somewhere.

So (assuming that's it) I could I just unplug that from the resistor and attach it to a 12-volt power source and bump test it?

 

[Ross Wooldridge]

Yes and yes.

 

[jmustian]

I'd recognize those water works anywhere, popular high school drinking spot in the east end back in my day haha.

Is this is the likely candidate wire? (Pictured red arrow) Seems to be the one, as it branches off from the rest of the harness. I will double check my wiring diagrams though, I have the chassis and the body manual hopefully it's in there somewhere.

So (assuming that's it) I could I just unplug that from the resistor and attach it to a 12-volt power source and bump test it?View attachment 713525

My green wire came through the pass side floor board and went over to the fan motor. Unhooked the connector about midstream of the wire and applied power and fan runs. 1969

 

[68yourker]

I just went through this same problem on a 72 New Yorker. I started off first out under the hood and jumped power to the wire going down to the blower, and the fan worked just fine (anything to do with the fan requires dropping the inner fender so I was very relieved when the fan worked). Does yours have air conditioning? There is a relay the power goes through. This fed power to the fan select switch, which was bad as well (pulled the switch and used an ohmeter to check function of the switch). Found an OE relay and switch, and everything worked.

 

[72Polara360]

Thank you for the replies I haven't had time to return to this due to weather and family obligations, but my next step will definitely be to jump power to the fan and see if it comes on.

I also need to check power at the harness attachment points at the resistor so I can confirm power from the switch, so far I've only checked resistance.

I didn't see a relay in the wiring diagram unfortunately that would have been a good failure point in terms of maybe not having to get the inner fender off , a potential outcome I'm not looking forward to.

 

[Big_John]

Thank you for the replies I haven't had time to return to this due to weather and family obligations, but my next step will definitely be to jump power to the fan and see if it comes on.

I also need to check power at the harness attachment points at the resistor so I can confirm power from the switch, so far I've only checked resistance.

I didn't see a relay in the wiring diagram unfortunately that would have been a good failure point in terms of maybe not having to get the inner fender off , a potential outcome I'm not looking forward to.

There is no relay.