heater wiring

[garyp]

My 39 dodge buisness coupe has a switch on the far left side of the dash and has 2 wires and a bulb 1 terminal is marked bat and the other mot 1 goes to the heater motor which I guess would hook up to the mot terminal but where would the other wire from the switch go and where would the other wire from the heater go? Would the switch wire marked bat go to the ign switch and the other wire from th heater motor go to a ground? I can not find any markings on the heater as to what the make is I took the cover off and looked and looked but no make or model.   Thanks Gary  

[Plymouthy Adams]

most aftermarket heater installs got the switch put where the owner wanted or where was common for the shop that did the install. connections should be on switched side of ignition so to not run down a battery should you park and leave the blower switch on.  

[Los_Control]

2 wires from heater motor is like my truck, 1 wire is grounded to the dash, 1 wire goes to the switch, like PA said, be sure and run the hot wire off the ignition switch to prevent a oops moment.

 

Correct me if I am wrong, I think you need 3 wires if you were to have a 2 speed motor.

 

[greg g]

Is the switch just on off or does it have a knob that decreases resistance as yo rotate it? If it's on off then from switched power to switch then switch to not to operate fan the other wire is likely ground. You can bench test it with your battery charger.  Hook the negative clamp to the heater body then connect to positive, does the blower work?  If it does it is self ground when mounted to the fire wall.  If it doesn't work, connect the negative clamp to the other wire.  You can do this test with 12 v without damaging the motor if one briefly.  If it self grounds then the Second wire might be looking for another signal for a second speed. Usually the fan switch has different positions which provide lower resistance through the switch to provide variable voltage to the blower motor. So the six volt switch probably probably puts out 3 volts for low speed and six though speed.   If they fail they usually default to no resistance to provide full to and highest speed from the bower.those universal rotary switches get very hot when running at low speed so make sure it is not mounted to any thing heat sensitive.  You might want to splice in an inline fuse on the lead to the switch probably a 20 amp fuse would be sufficient.

[garyp]

The switch has a bulb in it and a knob that goes over the bulb and seems to have 2 settings so the wire from the bat side of the switch goes to the ignition and I should put in a 20 amp fuse ok and the wire coming off the blower should go to ground. By the way it is a 6 volt pos ground.  Thanks Gary

[greg g]

Power feed should come from the accessory terminal of the ignition switch.  Wired there there is no chance that the heater will remain on after you switch off and remove the key.  The lighted switch probably came from an aftermarket or dealer installed heater setup.  Does the heater say Mopar on it stamped into the metal or a decal?

Edited November 29, 2018 by greg g

[garyp]

There are no markings on the heater at all it is too hard to see anything on the motor itself without taking it out but it looks in perfect condition I took the cover off and it looks like new inside in perfect condition. That is a good idea to hook it up to the acc side of the ign. will do. Thanks

[greg g]

Put up some pictures of unit and switch.