1968 Chevelle AC resisitor problems please help [Archive] - Chevelle Tech

: 1968 Chevelle AC resisitor problems please help

Oct 15th, 10, 4:22 PM
I am new to this site. I would like to say hello and thank all of you for your endless knowledge. Here is my problem any help would be great.

I am working on a 68 Chevelle. Some one took out the ac boxes out of the car both underdash and on the fire wall. I was able to track a good one and have since installed the AC. I am now to the wiring. The original harness was all there according to the 1968 manual. All was going smooth until I got on connecting the resisitor. The resistor on the AC box is a 4 pin connnector. My hahrness only has a rubber boot with 3 connections/wires.

After looking through many threads here I see where you guys broke down the color schemes and connections for the 4 pin connection, however I have not read seen anyting on the 3 pin connection. The part number that I have found online that would work with my wire harness is GM part number 3929055. Here it is: http://shop.stevescamaroparts.com/67-68-Camaro-blower-motor-resistor-fits-All-with-A-C-150275.htm

So my question is this. Should I get this resisistor and replace the 4 pin connector? Or should I track down another chevelle with this 4 pin wire harness and cut and splice mine? The ac box (under dasha and firewall) are out of the same car and I also have the AC controls out of that same car. I have my old ac controls that came original to the 68. Replacing the resistor the the 4 will this change the function of my controls?. I am building the car to look as origanal as possible, It is not a numbers matching car I have a 454 in it so numbers matching is no option here. Please assist in whatever you guys can.
I hope I made some kind of sense.
Thank you

Oct 15th, 10, 4:50 PM
How confident are you that your box and resistor came from a 68 ac car?

My 68 malibu ac car uses the 3 prong resistor, located on the firewall mounted air box in the engine compartment.

Your post confuses me.
You say the harness that was left in your car has the 3 prong rubbery boot(like mine) for the resistor. You link to a 3 prong resistor. You ask if you should buy that resistor, and change the connector from 4 prong to 3 prong. I thought you had a 3 prong connector?

Are you looking at the right wiring diagram? It's totally different for an ac car. I ask because the diagram shows everything, including the colors of the wires, all the switches, and even provide logic grids for the circuits due to the complexity.

Oct 15th, 10, 5:27 PM
If your car has the proper wiring harness (with a 3 prong connector) buy the resistor that matches. To use the 4 prong resistor you would need to add wiring , which does not sound right. And that would require a different motor speed control switch.

Oct 15th, 10, 5:53 PM
My 69 has the three prong resistor..

Oct 15th, 10, 9:16 PM
You have a 69 harness just make sure your control head is a 69 and all you have to do is get a 69 resistor.

Oct 15th, 10, 9:42 PM
Thanks for the quick response, sorry for the confussion. Let me try once more:

I am working on a 1968 Chevelle. The A/C set up that I have is either from a 71 or 72 chevelle. The set up is complete from the Heater box underdash, AC box that attaches to the firewall along with the switch controls that mount on the dash.

Here is the dilema. All my wireing connects to the system except for the resistor. My harness has a three prong (rubber boot) connector. The AC box (mounts on firewall)that I got from either a 71 or 72 cehvelle has a 4 prong connector.

I just checked on my AC controls (the ones that mount on dash to turn system on and off) and they are different from the 1968.

My question is Should I track down the 4 prong harness that and add wires to the system to run the 4 prong set up or should I just locate the 3 prong resistor, connect it and be done with it. THe later seems like the obvious choice but then would the blower work correctly. The controls from the earlier chevelle the ones that came with the AC set up have different speeds on them while the 68 chevelle A/C controls only have the options of OFF ----A/C----- OFF (this is the switch that sits on the far left that is verticle). I guess the question should be if the blower is interchangable from 68-72?

Should I worry about anything else once I swap the resistors and the AC controls?

I hope I made better sense this time.


Oct 16th, 10, 12:39 PM
the blower motor switch and the heater switch have the same color coded wires from 64-1978. there is a slight variation of color wires from 64-67. for your application there should be a YEL, LtBLU, and ORN wires running from the blower resistor to heater switch. as well, the ORN wire splices off from the blower resistor to the blower motor. there is a
4th wire, BRN, from the heater switch that goes to HTR fuse.
the blower motor, blower resistor, and heater switch should not be an issue. it is the way it is wired.
the AC controls should match that of your set up. i would highly recommend a wiring diagram. you have to be careful with this circuit due fire hazard.