Please help. My blower motor doesn't work on any speed. I removed the blower motor and it runs fine with 12V. I removed the resistor and all of the resistors have continuity of 1.3-2.4 ohms. I removed the AC control head (a big PITFA) and found out I had a short.



I have continuity from all of these wires to the fan (blue/orange, red and orange/black). I also have good continuity to ground on the black wire.



How does the fan switch get 12V? I have 12V at the fuse and the fuse is good but I don't get 12V at any of these wires with the fuse in place regardless of the key position.

Plus, does anyone have a part numberfor the AC control head? Or is it just a salvage yard piece? I will need the control head and the female receptacle that has the short damage. Apparently it is D5AB 14489 cc, but I can't find another part number or source.

BTW the switch in the AC control head doesn't work properly. I can put my multimeter on the ground position and I don't get solid continuity to each of the other terminals in various fan speed positions. I know my DVOM is a Lowes cheapy but I checked all of this multiple times. HELP!

 

You didn't state what year but all the wiring diagrams for early 80's show red/ orange, blue/ orange, and black /yellow go to the resistor with black/yellow also going directly to the blower motor for high speed. The orange/ black goes to the heater fuse for power but I see in your picture a solid black wire? It also shows that the heater fuse is actually a circuit breaker.

 

Please, when asking questions, list all the pertinent info, we are not mind readers.

Your "About Me" profile says 1986 F250. If this is what you're working on, the valve part number I posted is correct.

D5AZ-14489-C .. Wiring Harness Sleeve / Marked: D5AB-14489-CC / Obsolete

NOS PARTS LTD in Waxahachie TX has 2 = 972-937-2201.

GREEN SALES CO. in Cincinnati OH has 10 = 800-543-4959.
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Parts catalog pic doesn't show it, but bolted to the backside of the A/C/Heater control panel is this:

E1AZ-19B888-B .. A/C Vacuum Controlled Selector Valve Assy (Motorcraft YH-380) / Obsolete ~ 7 available NOS

1983/86 F100/350 & Bronco // 1981/89 Crown Victoria/Grand Marquis without Automatic Temperature Control.

All the vacuum lines connect to this valve that also contains the "kicker switch" for the A/C

When you slide the lever on the panel, this valve opens one blend door, closes the others. It also controls the vacuum operated heater water valve.

 

Thanks for the info. Sorry I forgot my truck specifics.

I think I need to make a trip to the salvage yard or order parts. I don't know why I dont have 12V on any of those wires. I suppose one of the wires could be open. All of those wires go from the shorted receptacle directly into the main dash wiring harness. I removed the dash cover which surrounds the speedo and gauges. It didn't really reveal any place the wiring could be open. I might have to dig deeper.

Also, all of my air doors were working correctly, it was just the fan speed switch part of the control head that was broken.

 

Does your truck have factory integral air, with the four vents built into the face of the dash? Or is it an aftermarket version? Those typically have vents under the dash.

Wiring diagrams are here:


1986 wiring diagrams


See section 32 for factory air. See 31 for heater only, and be aware some aftermarket air systems may have modified the factory non-AC wiring.

 

Thanks for the link. My truck has factory AC with the vents built into the dash.

I will probably tinker with it again on Saturday. It's been dang hot here in OK today.

Happy 4th of July to everyone!

 

The fan (blower) switch was available by itself.

D5AZ-19986-A .. Blower Switch-F100/350/Bronco: Use with heater or factory A/C (Motorcraft YH-264) / Obsolete

1975/78 LTD w/factory A/C without Automatic Temperature Control // 1975/80 Granada/Monarch w/factory A/C // 1977/78 Mustang II w/factory A/C // 1978/80 Pinto/Bobcat w/factory A/C

1978 F100/350 & Bronco from serial number CA0,001 // 1979/91 F100/350 & Bronco // 1980/91 Econoline except with auxiliary A/C

HAVEN FORD PARTS in Haven KS has 4 = 620-465-2252.

NOS PARTS LTD in Waxahachie TX has 16 = 972-937-2201.

GREEN SALES CO. in Cincinnati OH has 22 = 800-543-4959.

 

Amazon has it, among many other online sources:



Looks like Dorman has the connector you need, too:

 

You guys are on it like a rat on a cheeto!

Looking at a good wiring diagram I noticed my problem right away. I don't have 12V on the orange/black wire because I removed the blower motor! DOH!

Thanks for the parts numbers. I did order the receptacle and switch since I had that short. Truthfully, I think the fan switch was on its way out for awhile. The speed selections didn't work very well.

I will give another update when I rea$$emble everything.

 

I think you have already figured this out, but this circuit is a little different, power is fed to the dash switch, and then it is fed to the blower. So unless the dash switch is in the off position, the blower always has power. The speed control is on the negative side of the blower, so it's a little different to troubleshoot. The diagram is on page 142 in this link.

A/C & Heater - ???Gary's Garagemahal

 

Yeah, I a$$umed the switch would have 12V before the motor. My old man mentioned switching is often done on the ground side in automotive wiring for safety reasons. You think I wouldn't have trouble with this since I earn a living as an electronics tech for the FAA. Think about that the next time you board a plane.

Oh well. I need to get myself a factory manual for my truck. Using a Chilton's manual doesn't cut it.

 

If you do indeed have a 86, you can't get better than the factory EVTM we have linked to in this thread for vacuum and electrical troubleshooting. The factory service manual will have little more troubleshooting on certain parts of the truck, and it will have all the mechanical in it. There are 3 sets of manuals for this truck, the EVTM, the engine control and emissions, and the service manual which is sometimes a series of manuals, sometimes one big manual.

 

Well, i put the new switch and receptacle in and it fixed the problem... for a day. It worked fine this morning when I drove to work and this afternoon I have no fan speeds. The fuse is good and all of my air doors seem to work. I can hear them when I move the selector. I guess I need to remove the resistor and fan and check them again.

 

If you look at the diagram, if there was something wrong with the resistor, the blower should still work on high. You can see the switch directly grounds the motor out in hi, which bypasses the resistor.

 

You are correct sir. I will stop by the auto parts store and pickup a new blower (with lifetime warranty). Updates to come.