[72 ELCO BKSFD]

heater ac only work when fan switch is on low. quits on any other speed. a friend suggested it was the blower motor resistor. any other thoughts?

 

[CANTED]

That would be the first place to look. Could be the switch (less likely) The high speed is a separate circuit with a relay and in line fuse, right upper firewall area.

 

[JJLT1]

im not sure
check all the connections, grounds too,, and see if you have power to and from the switch??
could be the switch, or the relays stuck, or the resistor, or just a bad connection..

heres a diagram for a later model,, may be close,,you can get the idea..:texas:
http://www.maliburacing.com/wiring_diagrams/FourSeasonAirConditioner.jpg

 

[72 ELCO BKSFD]

thanks guys. i think i have deeper issues right now. i need to replace my heater core. where is the best place to buy one and does some one have a good procedure for r&r. i follow clear directions well (although my wife says otherwise).:beer:

 

[Lix]

Your in CA, so you can prolly hit up o'reilly.