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Help identify where this wire should be connected

4K views 6 replies 4 participants last post by  Blue Goose 
#1 ·
1978 C10 Silverado LWB factory 350sbc with factory A/C

I have recently bought this truck for my son and I to build together. I have an unconnected wire under the hood. I put power to the connector and the AC/Heat blower fan came on but I do not know where this thing connects.

In the photo the green wire coiled up with white tape is the wire in question (two wires into one). If it helps, The other green wire (one wire into one) below it goes to the coolant temp sensor. Any assistance would be greatly appreciated.
 

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#2 ·
Father & Son build #1

Hello,
I have a 1978 Scottsdale LWB, with a small block & a/c. I have a similar problem with the same plug, in particular, the wires that plug into it(double plug) are missing.
The wire (purple) that powers my blower motor has a black, round, rubber hooded, female connector that’s right beside the blower motor. Blower Motor is on the passenger side of the firewall.
I’m not sure about this but I think the single wire you referred to that’s dark green powers the a/c compressor. I’ve researched this to some degree but I haven’t been able to identify what the two-wires-into-one-plug services.
Also, I think the temperature sender wire is a dark green wire that comes out of the fuseblock.
 
#6 ·
I tried to attach a photo of my blower motor wire but was unsuccessful. My phone can’t resize photos that small.
The dark green wire goes to compressor.The light green wire goes to idle up solenoid to compensate for compressor load.The red wire that is cut off,if its coming from the small junction block\fuse,then it goes to the blower relay mounted on fender side of evaporator case.I would send a pic but I am also having trouble resizing
Use this re-size program for the re-size problems here. This is what I am using for the same problem. Here it is= www.picresize.com
Marvin
 
#4 ·
Ok that wire goes to solenoid that is mounted to the card.What it does is when you turn on a\c it energizes to increase idle to compensate for the load from compressor.Ir the carb has been changed to a Holley or Edelbrock then that would be why its not being used,Holley and Edelbrock both sell brackets and solenoids to fit there carbs
 
#5 ·
The dark green wire goes to compressor.The light green wire goes to idle up solenoid to compensate for compressor load.The red wire that is cut off,if its coming from the small junction block\fuse,then it goes to the blower relay mounted on fender side of evaporator case.I would send a pic but I am also having trouble resizing
 
#7 · (Edited)
78 wiring

See if this helps 78 a\c wiring Make note this diagram shows both,an a\c cutout pressure switch and a evaporator temp switch.You could have either one, but I have never seen both.These switches cycle the compressor to keep the system from freezing.Peronally I think the pressure switch is the best way to go.Many have a small screw between the terminals that you can adjust for cutout pressure
https://www.c10trucks.com/forums/attachment.php?attachmentid=4004&stc=1&d=1606068595
 

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