I have just rewired my 76 with a new 12 point harness. I had burned the old harness out due to a heater malfunction in the fan that burned the entire dash wiring and under the hood. The dash gauges and heater I am still messing with. For a supposedly easy harness it has been a pain in the rear.

Dash gauges: I am waiting on the 7806 voltage regulator to hopefully get them working again. I am still trying to find a way to install lights into the dash. The dash had shorted also so the copper plate on the back had been burned and the plug was not usable either. I am going to use the old dash and modify it so I have lights in it, speedometer and gauges.

The heater: I put in a new fan to resolve the problem with the short. I have good power to everything but nothing happens when I turn on the switch other than good power to all the wiring. I tested the switch with a light in the back and have power turning on to the various wires that go to the fan as I go from lo to hi, and I have power to the fan. I turn on the heater or A/C and get no action anywhere but power to everything.

The truck is a camper special, 1976 with a 360 in it. Factory heater and A/C. I have no idea how to troubleshoot the heater to track down where the problem may be. I turn on the heater or A/C and get no action anywhere but power to everything. Any help would be greatly appreciated.

 

If you have factory air you have two things that caused problems from day one.

On the passenger side of the firewall, is the heater temperature water valve that is spliced into the heater hose. It's vacuum controlled.

When you slide the control lever to heat, the valve is supposed to open.

This POS valve (it's black plastic & a gold colored steel), has a nasty habit of sticking closed. When this occurs, no water will flow to the heater core.

You want to verify that the rubber vacuum line that attaches to the top of the valve is OK, and not cracked.

D4AZ18495A .. Heater Water Valve (Motorcraft YG136) / Available from Ford.

MSRP: $28.72 / FTEpartsguy.com price: $17.23
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Bolted to the backside of the A/C Heater Control Panel is this little charmer:

D5TZ19B888A .. A/C Vacuum Control Selector Valve Assy. (Motorcraft YH285) / Available from Ford.

MSRP: $168.42 / FTEpartsguy.com price: $101.05

This valve is where all the vacuum hoses connect, all the damper doors in the A/C heater system are controlled by this valve.

When you slide the lever on the control panel, this valve opens one damper door, and closes another.

It also has the "kicker" switch on it that when the lever is slid to A/C, the switch "kicks on" the A/C compressor.

You want to verify that all the rubber vacuum hoses (7 or 8, can't recall) that connect to this valve are OK. After 30 years, some are prolly badly cracked.

The valve itself may be NFG. That was quite common when these trucks were new, and is still true today.

btw: I see that you live in Oregon...

FTE sponsor: FTEpartsguy is Ed Olson, parts manager of Parr Ford in Bremerton WA.

As you can see, FTE members get a parts discount.

 

I can hear the valves sliding open when I turn the lever to A/C on the selector. The hoses are all good and have been replaced. I will need to check the valve when it warms some outside. I can't get the fan to turn on at all. Would either of these stop the fan from working?

 

Nope.

I assume you've checked the fuse (AGC-30). If that's OK, then there's this:

Attached to the outside of the heater plenum chamber is the blower motor resistor, it may have burned out.

D3TZ19706A .. Blower Motor Resistor / Fits: 1973/79 F100/350 & 1978/79 Bronco / Obsolete.

Green Sales Co. in Cincinnati OH has FOUR = 800-543-4959.

Kinsel L/M in Beaumont TX has ONE: 800-816-2894.

Bob Allen Ford in Overland Park KS has ONE: 800-676-0675

NOTE: This resistor was only used on trucks with A/C.

F100/350's (and '78/79 Bronco's) with a heater only, use a different resistor.
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The blower switch could also be defective:

D3AZ19986A .. Blower Switch-Use with Heater or A/C (Motorcraft YH2)

Fits: 1973/77 F100/350 / 1978 F100/350 & 1978 Bronco before serial #CA0,001 / 1973/74 Galaxie/LTD w/A/C, w/o A.T.C. / 1974/76 Mustang w/A/C.

Available from Ford.

MSRP: $13.13 / FTEpartsguy.com price: $7.56.