Blower Motor - No high speed

[Ronbstewart]

High Speed blower Relay Checked ok even though I jumped the gun and purchased one (auto zone) oh well. Resistor tested bad, I always assumed high speed fan position some how by-passed the resistor, but there is a wire connection on resistor assembly that bypasses all resistance passes thru a diode and goes to motor, my diode won't pass current in either direction. my search yielded "Sarad Van & Truck parts" in Brooklyn, NY had it ($30 and some change includes shipping) This is standard part on older model Ford p/u and vans.

[Ronbstewart]

Finally bench checked Relay and Resistor, problem turned out to be the resistor. I was unaware that Blower high speed relay sent power thru Resistor assembly just not thru any resistance coils only a diode attached to the assembly, so either unit could cause a loss of high speed mode. I have a failed diode. Found one on a site in NY (Sarad Van & Trk parts) $30 and change after shipping (used on older model Ford vans & p/u

[Ronbstewart]

Finally got problem solved, there were 2 issue., High speed blower fuse wasn't blown just not making contact (that really put a wrench in my trouble shooting) it is labeled (AC) even though AC will work with out just not on high speed, clean that problem that high speed issue solved. Then all other speeds stopped. Problem was a burned out diode on resistor assembly. Picked up one from a starter/alternator shop ($2.41) Had a Electronic shop solder it an place ($10) and it works fine. A site advertised resistor on line for $40, but were out of stock.

[Ronbstewart]

A few corrections, high speed circuit is not routed through assembly and there are 2 blower fuses located in driver side front electric compartment.