Heater Blower problems

[sky6099]

I have a 72 plymouth 340 duster my heater blower and dash lights will not go on .. I found a plug in under the dash thats hot but there is nothing pluged into it..Its a Two prong plug in with four wires coming out the back.. I put a fuse in it just to see what happens and when I did that my blower motor came on, but it ran constantly and the heater switch would not control the blower at all and my dash lights also cam on.. Now I just need to figure out exactly what plugs into that two prong plug anyone have any Idea?

 

[TylerW]

I had to fix my blower motor, but for a different reason.

I suggest working backward from the fan motor to find out where the voltage "stops"

There's a fan relay mounted on the top of the heater box that controls the different speeds, so that has to be plugged in to the harness.

You really need to give additional information such as where this mystery plug is, and it's wiring color codes, then maybe someone can help further.

 

[cudamark]

That unit on top the heater box is a resistor, not a relay. A photo would sure help. I can't picture a factory wire plug that takes a fuse. If this is some sort of hotwire for the heater motor, then yes, it will only run at one speed. It needs a working fan switch and resistor to get more speeds. The dash lights are a completely different circuit. Most common cause of ALL the dash lights being out is the light switch or fuse. If just some of them are out it's probably bad bulbs or bulb holders.