Electrical questions

[Da67goatman]

I am in need of some really in depth knowledge on Suburban rear heat and AC systems.  I am currently working on getting my custom hidden rear heat working in my Burban.  I hid a tranny cooler under the AC blower inside the plastic cover and ran new PEX lines from front to back and hid them in the pillar.  I have factory rear heat and AC switches in my dash, but I added rear Defog and now I don't have enough space for all the switches and some of my converting doesn't allow the use of factory switches.  The problem I have now is that i want to use the AC blower for the heat as well as the AC, but not at the same time.  I want to basically separate the 2 parts of the stock rear Heat and Stock rear AC switch (vacuum and 12v) into 2 switches and combine the blower part of both switches.  I am trying to narrow it down to 3 switches, but I don't know enough to know if that's even possible.  One for heat on/off AC on/off and blower hi/lo/off.  I have a firm grasp on the vacuum lines, so I just need help with the electrical side.  I know the big purple wire is power for the blower motor, but that's the extent of my knowledge.  I need to know how the rear blower speed is regulated and if anyone knows how to get a switch for controlling vacuum.  I can guarantee I'll have more questions so all help is greatly appreciated.   i tried to include as much detail as possible but If you need something else I can provide. Thanks and I don't know anywhere else that I could get this information.  This forum is the best.

[VileZambonie]

I'm not following you. You have two rear blower motors?

[Da67goatman]

Sorry I wasn't clear enough, let me explain:  originally the rear heat and rear Air were separate units.  The AC was overhead and the Heat was on the floor, in the way.  I moved the heater core to right under the AC blower so it can draw the air across the core and blow it out.  I need to operate the original AC blower with both systems so it has to be separated from the Original AC Switch.  Then I will have one switch for heat, one for Air and one for the blower speed.  But I don't know enough to tap into the correct wires.  I need to know how the stock AC blower speed is regulated and which wires are for low and hi.  Wiring is not my strong point, so I'm going real slow and double checking everything so I don't screw anything up.

[VileZambonie]

It would help if you posted pix of your setup. Is your evaporator and heater core in the same housing now?

[Da67goatman]

Here's some pics, I don't have any of before, but I tried to represent it as best I could.  Yes both are in the same housing now.

[Lt.Del]

i'm gonna take a stab here.  You have the lo/hi switch on the dash by the ash tray i am assuming.  This operates the rear AC blower.
You want the blower motor to activate by itself without the a/c on necessarily.
Is this right?

In a nutshell, you would have to turn off your compressor from pushing refrigerant throughout the system.  

Unplug the two wire green/black wire from compressor under hood during winter months. There ya have it.

The dash switch only controls the rear blower in reality.  The cool air comes from the compressor circulating the cool pressure refrigerant throughout the system.  Kill the compressor from cycling and you kill the A/C.  

I think this would work.  

To make it neat and tidy, run two wires from inside to the A/C compressor green wire, install a switch inside, and you can kill the compressor with a flip of a switch.

Also, the kill the rear heat in the summer months, install a turn-off valve in the heat lines.

[Da67goatman]

Your close to what I'm going for.  I am installing Valves for the Heat, they are vacuum switches so I can stop the water flow in the summer.  You have the right idea with turning the AC off, but I want to do everything from inside the vehicle. I'll put a switch on the green wire and that will be for AC on/off, then I already have A switch for controlling heat on/off.  Thanks to Sgtdel I now only need to know how the Original AC blower speed is regulated and I can put that on its own switch.  Thanks Sgt.

[Lt.Del]

I now only need to know how the Original AC blower speed is regulated and I can put that on its own switch.

you're welcome.  Now, the rear blower is already on its own switch...that is the hi/low switch next to the ashtray.  Keep it in the middle and it is off. After controlling the AC compressor's green wire, and the valves for the heater, you won't need any more switches.  

The instrument panel's heat/AC/defrost controls does not have to be on to activate the low/hi switch for the rear blower.