1974 Duster 318 Factory Air

[1974PlymouthDuster]

Hey guys, finally took the plunge and switched to R134A...New receiver/drier, new expansion valve. All the goodies.

I'm having a problem with the blower motor. I can apply +12V to it, and it works fine. Other than that, no power.

I have a factory manual with wiring diagrams at home, but I wanted to reach out the best Mopar forum first...

Anyone have an issue with their blower motor wiring, and if so, any specific culprits I should run down before I start digging in to stuff this weekend?

Thanks guys!

-Ryan

 

[qkcuda]

Probably the resister in the heater box. It happened on mine. I had to find a good used one. If they burn out you will either get only one speed or none at all.

 

[67Dart273]

If it won't run on "high" it's not the blower. Much as I hate to say this, if you now know that the motor runs OK, and the fuse has power on both sides with the switch on (under load) it's likely either the swtich connector or in the switch itself

 

[RedFish]

In 73 and later models the fan speed select switch doesn't have an OFF position. Off comes from a separate switch that is operated by the upper sliding lever.
If my memory serves correct the blower motor has a hot wire from there and all controlling is done on the ground side of the circuit.

 

[1974PlymouthDuster]

my controls look like this if that helps. Id love to not have to get behind the dash [ame="http://www.ebay.com/itm/1973-1974-1975-1976-DART-SPORT-DEMON-DUSTER-A-C-HEATER-CONTROL-PLYMOUTH-DODGE-/181472756695?pt=Vintage_Car_Truck_Parts_Accessories&hash=item2a409e83d7&vxp=mtr"]1973 1974 1975 1976 Dart Sport Demon Duster A C Heater Control Plymouth Dodge | eBay[/ame]

 

[67Dart273]

In 73 and later models the fan speed select switch doesn't have an OFF position. Off comes from a separate switch that is operated by the upper sliding lever.
If my memory serves correct the blower motor has a hot wire from there and all controlling is done on the ground side of the circuit.

Separate switch, yes. Ground side, no. As I said, if the switch(s) is OK and the switch is actually getting power from the fuse, the damn thing should at least work in high

 

[mderoy340]

I hate to say it but the switch contacts are probably fried.

 

[1974PlymouthDuster]

I think the contacts are fine: I can distinctly hear the compressor clutch engage and load the engine when on AC or Max AC setting. I think this is pointing to the resistor QK mentioned?

 

[67Dart273]

I think the contacts are fine: I can distinctly hear the compressor clutch engage and load the engine when on AC or Max AC setting. I think this is pointing to the resistor QK mentioned?

Look at the diagram. This is in the AC section of the "heaters and AC" chapter 24.

The compressor and blower are serviced by SEPARATE fuses, and the power for the blower and compressor come off SEPARATE switch contacts

Here's the diagram out of the '73 manual, which is the same as the 74 shop manual

High speed blower has nothing at all to do with the resistor, unless it's a bad connection at the connector where the two wires junction. You could unplug the resistor and toss it in the garbage, and the blower would still turn fine in high speed

Black dots are the compressor clutch, yellow dots are the blower power

 

[Prine]

wiggle the FAN switch in/around HIGH......its the switch....

Mine will only run Medium or Low on the definite positions.....you have to wiggle the High Position to get it to kick into HIGH.....trust me.

:farao: