AC wiring issue now!

[El Chapo]

Hey out there these wires got tangled up in the fan blade apparently it was unplugged and moved while working on other things. Can you tell me where these wires end up/ get plugged into the connection to the canister is there see picture, but don’t know where the other end goes to or even what the connectors look like. Is this harness available I’ll need to replace or reman one with the right connectors.

Thx🤦🏽‍♂️

[Gary Lewis]

Oops, posted before I was done.

That switch is the Clutch Cycling Pressure Switch in the schematic below, and the LG/P wire goes back into the cab to the A/C controls and the BK/Y wire goes on to the compressor.

[El Chapo]

Oops, posted before I was done.

That switch is the Clutch Cycling Pressure Switch in the schematic below, and the LG/P wire goes back into the cab to the A/C controls and the BK/Y wire goes on to the compressor.

Thank you is that harness available somewhere do you know the part number or at least the connectors?

 

[Gary Lewis]

Thank you is that harness available somewhere do you know the part number or at least the connectors?

I don't know the part number of the harness nor the connectors. But you should be able to splice yours back together.

[FuzzFace2]

I don't know the part number of the harness nor the connectors. But you should be able to splice yours back together.

I dont know if the 81 AC harness is the same as yours or not, I am thinking not but .........

So first the 81/ 300 six harness for AC is a plug & play to a non-AC truck.

On a non-AC truck IIRC the blower motor wiring behind the dash is plugged together to work the blower motor.

You unplug this connection and plug in the AC harness and a wire or to to the HVAC control IIRC and the rest go out thru the firewall to the low PSI switch, carb kicker switch and the compressor.

Now why I say not is the early & later model compressors use different plugs and I think between six & v8 the compressors are in different placed? Also I dint know what EFI and non-EFI would do for the kicker going to the carb like on mine to raise the idle when the AC is on?

So as Gary said it mine be best to fix what you have unless you can find a harness for a truck just like yours year & motor size.

I know you can get the compressor pig tail for the later ones as I had to get one as I am using a later compressor and 2 wire clutch (power & ground). The 81 york compressor was a barrel type plug and the clutch grounded thru the body of the unit.

The carb kicker wire has a spade plug on it to fit the solenoid on the carb.

I dont have a solenoid (yet but have not been looking) so the wire just hangs out in the engine bay for now.

Hope that helps a little.

Dave ----

[El Chapo]

I dont know if the 81 AC harness is the same as yours or not, I am thinking not but .........

So first the 81/ 300 six harness for AC is a plug & play to a non-AC truck.

On a non-AC truck IIRC the blower motor wiring behind the dash is plugged together to work the blower motor.

You unplug this connection and plug in the AC harness and a wire or to to the HVAC control IIRC and the rest go out thru the firewall to the low PSI switch, carb kicker switch and the compressor.

Now why I say not is the early & later model compressors use different plugs and I think between six & v8 the compressors are in different placed? Also I dint know what EFI and non-EFI would do for the kicker going to the carb like on mine to raise the idle when the AC is on?

So as Gary said it mine be best to fix what you have unless you can find a harness for a truck just like yours year & motor size.

I know you can get the compressor pig tail for the later ones as I had to get one as I am using a later compressor and 2 wire clutch (power & ground). The 81 york compressor was a barrel type plug and the clutch grounded thru the body of the unit.

The carb kicker wire has a spade plug on it to fit the solenoid on the carb.

I dont have a solenoid (yet but have not been looking) so the wire just hangs out in the engine bay for now.

Hope that helps a little.

Dave ----

Thank you guys a friend helped me figure out my ac wiring issues looks like the previous owner had bypassed the switch and had relays and was running it in a single speed.

So now my issue is that it’s blowing air mostly through the top of the dash like in defrost mode and very little is coming out the vents. As I move the lever control back and forth it doesn’t seem to have any effect. I checked vacuum lines and from I can see they are ok and in place. Any suggestions?

[Gary Lewis]

Thank you guys a friend helped me figure out my ac wiring issues looks like the previous owner had bypassed the switch and had relays and was running it in a single speed.

So now my issue is that it’s blowing air mostly through the top of the dash like in defrost mode and very little is coming out the vents. As I move the lever control back and forth it doesn’t seem to have any effect. I checked vacuum lines and from I can see they are ok and in place. Any suggestions?

The system defaults to Defrost w/o vacuum. So my guess is that something in the illustration below is disconnected or broken. The vacuum hoses shown as 17A543 need to be connected, and it isn't unusual for the one going through the grommet at the firewall is broken.

[mat in tn]

The system defaults to Defrost w/o vacuum. So my guess is that something in the illustration below is disconnected or broken. The vacuum hoses shown as 17A543 need to be connected, and it isn't unusual for the one going through the grommet at the firewall is broken.

there is a simple method that ford used containing a circuit of vacuum operated motors (diaphragm type) which gets controlled through a vacuum switch in the dash control panel. the switch in the control panel gets vacuum from the engine off of a tee on the firewall connected to the intake manifold. i know i said simple but after you study it a little you will get it . if any part is disconnected the vacuum loss will allow the motors to relax into their "normally off" position the same way a relay relaxes when de-energized.

that said look over all vacuum hoses from intake to firewall and you will notice one which is about 1/8"-3/16"that enters the cab through a flex conduit along with some wires entering above the factory ac box close to the heater core hoses. that is the one feeding control vacuum to the switch. obviously if this change happened after working on something, focus on the area you were working in. next if you did not work on any part in the dash then its possible the vacuum switch has deteriorated. but if it was working before then its most likely a mishap that you can find easily. 40 year old plastics are very fragile!

[El Chapo]

there is a simple method that ford used containing a circuit of vacuum operated motors (diaphragm type) which gets controlled through a vacuum switch in the dash control panel. the switch in the control panel gets vacuum from the engine off of a tee on the firewall connected to the intake manifold. i know i said simple but after you study it a little you will get it . if any part is disconnected the vacuum loss will allow the motors to relax into their "normally off" position the same way a relay relaxes when de-energized.

that said look over all vacuum hoses from intake to firewall and you will notice one which is about 1/8"-3/16"that enters the cab through a flex conduit along with some wires entering above the factory ac box close to the heater core hoses. that is the one feeding control vacuum to the switch. obviously if this change happened after working on something, focus on the area you were working in. next if you did not work on any part in the dash then its possible the vacuum switch has deteriorated. but if it was working before then its most likely a mishap that you can find easily. 40 year old plastics are very fragile!

Wow you guys are rock stars!! Know your stuff I probably would have given up on this retirement project and gone back to woodworking. And it was as y’all have pointed out broken line on the firewall I must have done that while doing other things maybe I get so focused that I forget that everything is easily broken in a near 40 year old car. Again thank you thank you both Gary & Mat. I would love to meet you guys someday in real life.

Peace… Steve “ el Chapo”

Ps good timing it’s gonna be 100 degrees later in the week here 🥵

[FuzzFace2]

Wow you guys are rock stars!! Know your stuff I probably would have given up on this retirement project and gone back to woodworking. And it was as y’all have pointed out broken line on the firewall I must have done that while doing other things maybe I get so focused that I forget that everything is easily broken in a near 40 year old car. Again thank you thank you both Gary & Mat. I would love to meet you guys someday in real life.

Peace… Steve “ el Chapo”

Ps good timing it’s gonna be 100 degrees later in the week here 🥵

Dont feel to bad I was also working in the engine bay and the HVAC was working 1 min. and not the next

I started checking for vacuum and had it up to the firewall in the engine bay but not inside the truck?

After an hour of checking I found the plastic line broke as it went thru the rubber grommet.

Had a heck of a time trying to push a rubber hose thru to get vacuum to the HVAC controls.

Dave ----