48 p15 heater help

[whippersnapper48]

I pulled the old aftermarket heater out of the car because of a leaky core. when it was hitched up, the fan worked. I got a known good original heater from a friend of mine that worked when hitched to a battery. sadly nothing now that its in the car.  The switch is good, and its a two wire one.  

 

Thoughts gents?

 

Jon

[whippersnapper48]

[Conn47D24]

If it worked on the bench, maybe it's a poor ground?

 

That's been advised here many times.

 

?

[desoto1939]

Clay I would have to agree might be bad ground becasue the car was just painted. I had this happen after my 39 was painted. One of my rear taillights would not work so I hooked an additional ground wire to the taillight bucket and the light worked. When the car was still original paint has worn away and this sometimes causes you to get a better ground. So use a jumper cable with allegator clips when in the car and ground to a good clean bolt or have a bolt that uses a start washer to cut into the paint.

 

Rich Hartung

[whippersnapper48]

The car is 100 percent original. Including paint and upholstery 

[Dan Hiebert]

Could still be the ground.  I pulled the aftermarket heater out of our D24, but that was so long ago I don't recall where it was grounded to.  I pulled a MoPar Deluxe model 36 (same as yours) out of a parts car.  As far as I know, it was the original mounting, but what I found odd is that the motor was grounded to the body of the heater.  Technically, as long as the grounding circuit makes it back to the battery, that would work.  But, since this heater is not original to our D24, I didn't trust that ground to the heater body, too much potential for insulation between the heater and the rest of the car, so I grounded it directly to the car body.  To shorten that tale, if your model 36 heater is grounded to itself like mine was, move the ground to someplace on the car body behind the dash. 

[whippersnapper48]

I have an aftermarket switch that lights up when switched on. It lights up when the ground is not connected. When connected to the frame,the light goes out. Very odd

[greg g]

Those old aftermarket switches aren't robust enough for 6 volt operation, especially those with a rotating dial.  Make a jumper wire out of ten gauge wire with an inline 20 amp fuse. Power the heater directly from the accessory terminal of the IGN switch.  This should power the fan on its high speed setting, which is the default.  The original switch works on resistance to decrease voltage reaching the fan to reduce the speed. Those aftermarket switches supposedly do the same thing through a resistance winding, but they create a lot of heat and can be dangerous.

 

After you determine the fans runs when powered through the jumper then you can source a different switch.

 

You also may want to consider running a ground cable from the body to the engine or frame.  This will improve the performance of all body grounded electric accessories.

[Sniper]

Pretty much all blower fans, up till very recently, used resistors to control the fan speed.  Later model ones had resistor packs mounted to the heater box and the switch just chose which resistor it fed.  For example, my wife's old 2005 Ram used a resistor pack, mounted in the air flow of the HVAC box, to control fan speed.  Now days it would not surprise me if they used some sort of computer controlled PWM setup to do it instead.  Wouldn't be hard to retrofit a PWM circuit into our old stuff, giving you infinite fan speeds.

[whippersnapper48]

Greg, we have successfully solved the problem. The fan is whirring at top speed! Who do you recommend for getting a repop switch from?

 

Jon

[greg g]

Luckily my switch is fine.  Can't really recommend an after market one.  There are a few used and oder aftermarket ones similar to stock on eBay.

[Doug&Deb]

May want to try locating an NOS switch. More expensive but should work better.