ok I finally found a harness at the junkyard but im a little confused. The donor vehicle was a different year but the setup looks identical so I snatched it. Im not sure if the different years used the colored wires in a different area. on my model the light blue plugs into the top connector of the resistor and the pinkish brown plugs into the middle whereas the donor harness plugs in opposite? The Dark brown on my original harness is cut and the donor plugs into the slot that is empty on my resistor. was thinking of wiring it directly to that open slot and see if I get any lower speeds. The green wire appears to go to the ac canister which im assuming is the condenser? which I don't have on my vehicle. wondering if I can bypass the green wire completely. Any ideas if the Dark Brown wire not plugged to resistor might possibly be my culprit?
You're good to go. The same resistor stack was used with the C60 system from 73 -91 (P/N 336403).
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However, you are correct about the wiring colors - there was a change over the years. But it only effected the 12 volt power supply (the one at the top of the "pyramid"). It was YEL in earlier models, but at some point it was changed to BRN/WHT. The color of the other three leads remained the same: LT BLU in the middle, DK BLU on the bottom left and TAN on the bottom right. Exactly as shown in the images that Andy provided.
Here is your original schematic:
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An example using the 1986 system diagram:
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Just a little advice: the wiring in your truck is a mess. I would disregard everything associated with it (i.e. wire colors, terminal connections and especially - the splicing methods used). Butt splices are bad medicine!
BTW - there are no GRN leads involved in the blower control circuit. The LT GRN is 12 volts to the low side control switch (located on the filter/drier). There should also be a DK GRN that exits the control switch and then supplies the compressor clutch with power when pressure in the low side rises above 46 psi. When it drops below 25 psi the power is cut off.
Control of the refrigeration cycle (on and off operation of the compressor) is done with a switch that senses low side pressure as an indicator of evaporator pressure. During air temperatures of 60-80°F, the equalized pressures within the charged air conditioning system will close contacts of the pressure switch.
When an air conditioning mode is selected, voltage is supplied to the compressor clutch coil. As the compressor reduces the evaporator pressure to approximately 25 psi , the pressure switch will open, de-energizing the compressor clutch. As system equalizes and the pressure reaches approximately 46 psi , the pressure switch contacts close, re-energizing the clutch coil.
