Look on page 142 in this link.

A/C & Heater - ???Gary's Garagemahal

That's for a 86, but a lot of it was the same. I see a brown white power wire and a brown/orange going to the blower motor. The blower motor would probably have large fat wires, since it shows a 30 amp fuse for this circuit.

 

The colors sound right as the 2 in a loop are brown/orange. You unplug them and plug in the brown/white wires into them.
I don't want to cut the tape open to see if there is a junction splice that picks up the black/yellow & green/purple that end up in the engine bay.
It's just Strange I have all them cut brown/white wires and they don't go to anything.
thanks
Dave - - - -

 

Thanks Dave,


As happens more than once it helps but also adds more questions.
I see C606 & C606A is the loop of the standard harness and when adding AC they unplug them and plug in this AC harness.


This harness besides having the br/o wire changes at S603 to a br/w.
Now after the "AC/Heater function selector switch" the wire out is br/o (blower motor) and gr/p for the AC clutch side.


What I don't get is why all the br/w cut wires in my picture and where do they go to.
Does the AC harness have it's own plug and you don't use the standard harness plug?
I have to dig out all the control panels and see if the fan switch plugs are different as I don't remember seeing any place on the AC panels to plug in all the br/w wires.


Closer but not there yet.
Dave ----

 

Ok I "think" I may have found the answer I need on the cut wires of all places LMC site.
Truck Parts and Truck Accessories


It looks like the fan switch is the same for AC and non-AC systems as does the plug/pig tail.


My thinking has been and still is you un-plug the BR/OR looped wires and plug this AC harness in to the 2 looped wires.
The AC harness has a fan switch plug that after unplugging the non-AC plug from the fan switch you now plug this AC plug into the fan switch.


If this is so, still need someone to confirm the 2 plugs, I can buy a new pig tail and splice it onto the wires but brings up another question.
What is the pin out of the wires to the switch?
Anyone have that other page (page 151?) in the link for the switch pin out and does it include the AC harness?


Thanks
Dave ----

 

All of my FoMoCo documentation - including wiring diagrams - is all in plastic tubs/storage bins someplace, I really don't know where other than in what was a bathroom at one time.

Fuzz - you might go ask on Gary's site, here's a link to the HVAC section of the 1981 EVTM hosted on his site:

Heating, Ventilation, & Air Conditioning - ???Gary's Garagemahal

What you say - in general - sounds familiar... I remember the AC harness piggybacks onto the main harness but IIRC the AC harness changes some functionality of the fan switch, e.g. the fan is never allowed to turn all the the way off while the AC is on to keep from forming ice in the cooling system. Regardless, the AC harness is just an add-on, and you route the heater blower motor circuit appropriately (kinda fat, single-conductor plugs IIRC).

The brown/orange color combo sounds familiar for the heater fan.

Dealer-added AC is a whole other installation, with an additional blower motor just for when the AC is on; I'm sure the installation makes sense in somebody's mind but I didn't like it.

 

Did you look at page 101 in this link?

Component Testing - ???Gary's Garagemahal

 

Thanks guys
When I get on my computer, on phone now, I will check the link out.

Gary did try and help but the colors did not match up. I may need to pull that AC / cut wire harness out to check it better on the bench and then come up with a game plan.
Thanks again
Dave - - - -

 

Dave, I did look at that information before but did not "look at it" as it did not have the color wires I was looking for
BUT..........
I just looked closer at page 100 and it does list the same color wires under the "terminal locations" (pin out?) but I don't know where that would be in the truck?
It kind of looks like it would be part of the AC switch panel but when I gave a quick look at it I did not see any other fan/AC switches that would take a plug.


If it is a plug for a switch I don't think it is the fan switch as it is a different shape. The fan switch plug looks like the one on page 101.


I really need pull that part of the harness to get a good look it all.
Dave ----

 

I looked at the information again and I got it!
the cut wires go on the end of the HVAC selector switch.

Thing is the links pin out of the socket/plug is square and mine are in a line.
I am closer than before!
Thanks guys for the help.
Dave G.

 

Being closer than before is a Good Thing.

 

Gary and another member posted up the pin out for the in line plug.
Also a link to said plug but they list 2 that look the same but give no details on them.
I will make a post on the part numbers to see what one is right.
Dave - - - -