I installed a factory a/c unit in my truck in went ok. i have 2 wires left to hook up and can't figure out where they go. one is orange and the other is red both are kind of heavy gauge wires i then see the same gauge orange wire and color going into the heater switch do i splice the wire into it. the red wire i am at a total loss it runs from the heater control all the way down to the heater box.

 

Hey! I just did the same thing to my truck. I got every wire hooked up, but I had to do a lot of learning about the different year model wiring harnesses.
Send me more info and I can hook you up.
What year is the truck? I'm assuming 75...right?
What year model is the harness that your trying to use?
Does the harness have a little silver relay that bolts to the bottom lip of the dash board?
Don't worry a bit. We can fix this pretty easy.
Doc
ON the main cab harness between the dash board and the fire wall where the old heater control panel plugged in, you should have bullet connectors. correct?
Now, on the A/C control panel harness that your pluging in now, does it have the same bullet connectors, or does it have the spade connectors?
On your orange wire, what type of connector is on it?
On your red wire, what type of connector is on it?

 

the main harness is all sealed up in tape and i am using parts from a 77 bronco the panel has spade terminals and so did the stock one the orange one has a plastic quick connector on it . the red is bare i cut it out of the main harness on the junkyard bronco.

 

Does your harness have a little silver relay box that bolts to the bottom lip of the dash board in front of the passenger seat?
I'll be back with more info shortly...hang tight

 

That big red wire that you mentioned....does it have a black stripe?

 

i'm not sure what little silver relay you are talking about. the red wire is a solid red it appears to supply power down to the rheostat on the air duct along with the stock 3 prong that was used with the heater

 

That big red wire that your talking about has a black stripe on my truck, and it goes from the rheostat that you mentioned up to the control panel blower motor speed switch.
Forget all about the relay. In my haynes manual it doesn't show the broncos to have it.The red and orange wires....everything is plugged in except them to the control panel?
Doc

 

Do those wires show up in the illustrations I posted in the other AC thread ?

 

Dennis, I'm sure they are in that second picture (the one for under the dash) but I cant tell for sure because the wires arent labeled and it's hard to see where they are going. I'm pretty sure I know which wires he's talking about, but I can't remember for the life of me where they end up at the control panel. I'm half tempted to take my guage bezel back off to get a refresher course.
One problem is my wireing harness came from about a 77 model truck. The 75 -77 trucks had a relay between the blower switch and the blower motor. His harness came from a bronco, and my Haynes manual doesn't show the Bronco to have the same type of relay.
The red wire and the orange wire he is talking about should work like this: there is a big black plug that goes to the blower motor switch. The orange wire and red wire are both on that plug along with a green wire. The green wire is no problem he already has it. the orange wire is a short wire that goes from that big plug and should plug right in to the harness where his heater plugged in to before. The red wire is 2 wires in one place on that big plug. One wire goes to the box on the passenger side, the other wire is a short wire like the orange one that should also just plug right in to his main harness. That's the general idea of how mine worked.
Doc.

 

maybe i should unwrap the main harness and see if these wires are inside.

 

well i see in mil1ions post in another thread he circled the group of wires i am talking about it is the single red one that runs up the harness with the green one and then plugs into the back of the control panel.

 

Gashog,
Read my previous post again (number 9)
The red and orange wires do go to the big black plug for the blower motor switch. They both have short wires coming off of them that plug in to your main harness. Look at your main harness for a big brown wire. There should be bullet connectors on that wire. The Two bullet connectors may be plugged together. One is male and one is female. The 2 short wires coming off of the black plug (1 red, 1 orange) will plug in to the big brown wire. Either the red or the orange is male and the other female. Therefore they can only plug in one way. Don't unwrap the main harness, just look for the big brown wire and plug in there.
Doc

 

well after checking twice there is no wires like this in the harness do both the orange and the red supply power then if so could i just hook them up to the battery with a fuse in the line and yes after checking i saw the red wire has a black stripe.

 

Gashog....Hang tight a little while. I will reconsult my wiring diagrams, and if that doesn't work....I'll pull my control panel out to double check, and send pictures if necessary.
Doc

 

ok i found the big brown wire it has bullet connectors so do i unplug them and plug the orange and the red inbetween them. the orange and the red don't have bullet connectors but thats probably becasue it came out of a bronco.