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BN2 Heater motor and Switch/Rheostat

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mbrooks

mbrooks

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Decided to pull out the non-functioning heater this afternoon. I know it's far too hot to need a heater in Houston in June, but I like everything to work!! Anyhow, I pulled the motor apart and discovered one of the brushes was stuck. Freed this off, cleaned the commutator, rebuilt it, stuck 12volts on the leads and hey presto!!

My question concerns the wiring of the switch/rheostat to the motor. I know it works both with the switch/rheostat in either the ground side or the live side, [I hooked the whole circuit up outside the car and it worked both ways] but to be correct, which should it be? The wiring diagram only shows the wiring to the heater as a complete unit.

Thanks in advance

Mike
 
Hi mbrooks, Contrary to most british engineering a load should be switched on and of by breaking and making the hot [Ungrounded] side of the circuit,-FWIW---Keoke /ubbthreads/images/graemlins/grin.gif
 
As you say, it probably doesn't matter. On my BN2, at the back of the heater, there is a green (hot) harness wire with bullet connector that connects to a black heater wire. This black wire goes to the front heater panel in a vinyl sleeve & through a grommet in top of the panel to the rheostat. The return wire from the rheostat goes to the back through this same sleeve & into the motor. No wire joints between rheostat & motor.

There is a second black wire from the motor that has a bullet connector to connect to a ground in the harness. Check which is which harness bullet connector before installing the heater. You can't tell, once things are in place. The heater pipes have grommets around them where they go through the firewall. A real bear to keep in place when pushing the pipes through the firewall.
D
 
Thanks Keoke and Dave. Yes, that all makes sense - the switch/rheostat is on the hot side. Dave, the info on the internal wiring between switch/rheostat and motor was useful - I could see that the wires had to go outside of the unit by the grommets, and the fact that if one wired it internally, the fan blades would chew it up! But I didn't know about the vinyl sleeve and that there were no connectors - my black wires had been cut. I will run new black wires, soldered at the inside of the motor.

Thanks again

Mike
 
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