Heater Fan- Reg heater vs AC Heater

[tjvending]

I'm trying to get my Heater Fan to work. Someone has put in a Non-AC controls and all of the wires are un-hooked. My question is , I'm trying to get the heater to work to get the windshield clear in the mornings. Can this be done by using the non-AC control? Most of the AC items are unhooked. I can feel heat (stays on all of the time) but how do I get the blower to come on and work? Let me know where I should start, Thanks,

TJ

[JimKshortstep4x4]

Your problem could turn into a project because of the way the AC blower is wired up. The three speeds all run through the relay which is over to the right hand side of the heater box. I am attaching a picture of the AC heater wiring so you can see where the relay is located. You will need to get power to the relay somehow unless it has been taken out of the circuit, also.

Take a look at your wiring and let us know what you have as far as the AC wiring. Another problem you can run into is the defrost is controlled by the diverter box so even if the blower is working air may not go out the vents.

Jim

[tjvending]

Here's some pictures of the wires, let me know were they should go, TJ

[JimKshortstep4x4]

Someone has left you quite a mess!

I don't know where to begin telling you what to do as the external AC wiring has been balled up with the other internal AC wiring and there is the extra wiring that someone has installed. I have never seen anything like what you have!

Sorry,

Jim

[tjvending]

If I can get a copy of the Schematics for the heater/AC controls, maybe I can figure it out. Where can I get this information for a 72 Chevy?

TJ

[tjvending]

Jim,

How about the white plug in the last picture, where might this go? Let me know if you know more on the others, any answers would help. I trying to get the blower and heat to work for now, not worried about the AC
TJ

[haysonj]

Here you go if you need more let me know as I just rewired my entire truck. For the AC there are vac lines and you also have three cables that control diverter doors for AC, defrost, and heater/AC vents

[mrein3]

To start with, you need to plug the 3-wire female plug with yellow, light blue and dark blue wires into the 3-pronged male resistor block on the heater behind the glove box.

That should help you start putting the puzzel back together. With the diagram posted by haysonj you should be able to trace all the wires and plug them into the right places...
that is of course if the previous owner (PO) left all the duct work and controls in place.

The 2 gray wires going into the one female connector in the picture just to the right of the connector I circled is probably the wire that goes to the light that lights up the heater controller. If not it probably goes to another instrument light of some kind. Gray behind the dash us usually instrument lights.

The two-wire female connector with green and black wires that is between the circled connector and the gray instrument light connector looks like the plug that plugs into the compressor under the hood. If your AC isn't charged up under the hood, just tape this one off and start planning on restoring your AC system.

When I got my AC style heater fan to work properly, the switch and connector behind the switch on the control panel was melted. When I started scouting junk yards all the ones I found there were melted. I ordered a new switch and connector from a supplier, re-did all the wire ends, and got it all freshened up.

You don't need the AC stuff hooked up under the hood for the heater part of your system to work. You do need all the wires and all the ducts however.

Looking at what I can see from your pictures, I'd say you're lucky. At least the PO didn't cut all the wires.

[tjvending]

Its starting to come together, wire are falling into place. I have another question for you, how about the big orange wire (Main power- 12OR) and the Gray (Light 20GY), both have two ends with clips, how do they go into the Fuse Panel? Let me know, I;m almost there. TJ

[haysonj]

the orange wire goes where the cig lighter is in the fuse panel and then you plug the lighter into the orange wire. The grey wire does the same thing with the panel lights. You should install a 25 amp fuse in the cig lighter slot

[tjvending]

Got the Orange wire and Grey wire hookup today. Both seem to be working. The Light come on for the heater and I have juice from the relay (Orange ). Now I have to get a heater/air control unit because I only have the regular heater unit, seems my plug won't work because of the air setup. Also I took a hot wire from the battery post and touch the post of the blower but it won't work, maybe the blower is bad??? Question: is there a difference in the Heater vs AC Heater controls cables, are they the same?

TJ

[haysonj]

You need to make sure you have a ground on the blower. If you look at the schematic it gets its ground from the relay along with the power wire. there is a seal on the blower motor that keeps it from grounding through the truck body. try a ground wire from blower housing to battery. As for the cables I don't know what the difference is but there are two different part numbers for them

[tjvending]

Had to relocate the ground wire like you said, with the hot wire touching it now fires up. Waiting on my Air-Controler to come in, hopefully everthing will work. Question:On the main plug that goes to the air-Control, should one of the wire be hot with the key on or does it just work when plug into the controler?

TJ

[tjvending]

Receive my AC Contoller today, When I went to install the bolt holes under the dash won't match the holes in the Controller. Do you think its the correct one for the Chevy Truck? Should it match up with the two large holes on the underside of the dash? Next question. I plugged in the 4 wire prong and turned the key on and switch on the fan switch but nothing. What should I do next? I thinking I'm not getting any power to the 4 wire prong. Let me know my next steps. TJ

[haysonj]

If you look at the schematic there is a #14 brown wire from the fuse panel to the switch (shown dash line) Make sure it was not in the other plug that you could not plug in. they may have used it to run the other controls. If you can't find it try running a fused wire from your Acc. switch to the terminal shown. If you have a ac cab and an ac controller the large holes will line up. You may have a controller from a later year. cant know without seeing it

[tjvending]

They did used the brown wire on the heater switch. Here's some pictures... Also of the mounting, it doesn't line up to my holes. TJ

[haysonj]

Like I said earlier you need to reconnect the brown wire in its original spot or to the Acc side of the ignition with a 15 amp fuse. those controls don't look anything like mine. Mine has a metal bracket on the bottom of it yours is drilled in the casting. You may need to find the metal bracket if it is not on your heater only control. Here is a picture of what the face should look like and I'll try to get a picture of the bracket tomorrow. Your face is the same except it is white with black letters where mine is black with white letters.

[tjvending]

Hatsonj,

Hooked up the wire (Brown) like you said. I now got power but the blower only works on the third click down (I think Med). What do you think, relay or should I try something else? I 'm getting close, almost working ( at lease the heat part), thanks to your help! I still need to get the cables for the ducts and the bracket to get this thing mounted in. TJ

[haysonj]

It's probably the resister that is inside the heater box. I doubt its the relay because the fan would not run at all. You have to pull the duct work to get to the resister. Make sure all wires are connected to it.

[tjvending]

I replaced the resister with another, still same thing, comes on med 3rd click down. The one I just put in looks to be in good shape, the one I pulled was kinda bad looking, on its last leg. Another question on the plug that go into the controler. Should there be two yellow wire? Look at the picture, I have total of four wires, 1 Lt Blue, 1 yellow, 1 or, and the brown. TJ

[Andy4639]

Change the switch on the control panel. They go out often.

[tjvending]

I just got the controller and was supposed to be totally rebuilt. That should included the switch, wouldn't you think? It came with the switch.

TJ

[71 super]

Change the switch. As far as your control itis correct but you need a bracket to adapt it to the dash. Don't worry this, was a stock thing so you are not the only one out there with this bracket. I will look and see if i have an extra, if I do you are welcome to it. I will check tomorrow and see if I do. If I do, pm me your address and I will send it to you.

[haysonj]

Your other yellow wire is spliced in somewhere in the harness and goes to the switch for the AC compressor so you end up with a yellow at the resister and the AC compressor switch. You can take a short wire and jump the differant spades to the brown wire to see if its your switch

[CCCC]

Nice work. This thread is a good example of willing and patient guys assisting an earnest member who needs and deserves help. Thanks.