Heater/ AC wiring

[matt030305]

Could somebody guide me through what brings power to the heater/AC within the wiring diagram? I have tried a bunch of things and to no avail. Not really electrically savvy. I know that there is a accessory wire that will turn on the blower motor but where does it connect through to the resistor? I will attach a wiring diagram below and if anyone could help it would be greatly appreciated! Thanks!

 

[harrisonm]

For us to be able to help you, we need some information.
1. What is the Make, Model and year of the car.
2. What is the problem? All we know is that you said, "what brings power to the heater/AC", and that you tried a bunch of things.
Do you mean the fan motor isn't working? Do you mean the AC clutch is not activating? There are a lot of things that can happen. Give us as many details as possible, and let us know what the "things" were that you tried.

 

[matt030305]

well to start- it was originally a slant 6 70 duster with AC. Now it is a 340 without ac (just a standard blower motor) Due to the PO taking shortcuts in terms of wiring, it caused many wires to either be cut, scattered or just completely gone from the harness. At this time I am just trying to get the heater to work properly. Here is a list of details that I’ve tried.

1. Hooked up the blower motor to the battery and it does indeed work
2. Attempted to rewire but I have no idea what wires beings power to the actual unit and resistor.

I would just like a guide on how the circuit functions in order to get it up and running again.

 

[townsend]

First you need to check the fuse box.
Look at the wiring diagram in the 1970 service manual on page 8-139. Look at fuses A and B and test for power on both sides of the fuses with the ignition on. They should be labeled ac and heat on the fuse box. Might be a good idea to check all the fuses anyway. Let us know the results.

 

[Mattax]

He's the guy with a later white fuse box in his car.

Here's a schematic showing the power supply route for a '70.

In general, the car's two power supplies are joined at a welded splice, and the feeds from their go to the key switch, hot side of the fuse box, headlight, and in '70 the horn relay.

The diagram from the FSM shows the wiring for an A/C heater optioned car.
Not shown on that diagram is the power to the fusebox. We can just add that in. Heater was always switched so its the wire Q2A

Wires C1 and C1A were 14 gage Black and 18 gage Light Green.

You can test for power to the fusebox and other switched accessories by putting the key in Accessory position. That will save power and keep from heating the points and coil or ECU and coil.

The ammeter can be a useful tool as well.
When the engine is off, anything drawing power will show as battery discharge.

At the same time note that any wire attached to the mainsplice is connected to the battery. If they are accidentally grounded, the battery is getting shorted.

Anyway the next thing to look for is if the previous owner left the heater from the A/C unit or installed a non-A/C heater.


edit:
From the main diagram. Non A/C heater looks to use the same C1 (14gage black with stripe) wire to the heater switch.

Also it shows a three position buss, in which case the jumper to the extrqa fuse for the A/C optional light green wire wasn't needed.

That seems to match what this guy shows in the fusebox from his '70

You will only need the power to the heater switch if using just a heater.

 

[townsend]

OK, didn't notice he had two threads on same subject.

 

[Mattax]

Here's photos of a non-A/C heater the sellers claims are from a '70

Green wire is power from the reisistors to the motor.

The brown wires are ground.
I can't be sure '70 is the same but one of the brown wires runs along the back and under the passenger side kick panel where it is screwed to the body with a ring terminal.

More likely, the combined A/C Heater unit was retained.
The power to the blower motor on those is routed to the engine compartment.