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Wow . Ton of info, I tested the switches again and in MAX THE FAN DOES NOT OPERATE. Max only ! I too can operate the ma fan on HIGH ) switch from max to defrost several times(back forth) to get max operating correct . And yes in vent the fan operates .As stated before when I put it in max I actually hear the compressor kick on(as in norm).but no fan ,swap it to norm fan acts as it should( usually on high) .Oh and a few times I have had it in max WHILE traveling down a rough dirt road it will quit .I did not mean to confuse any one with the blend door issue that I experienced a few years back Thanks TR
It sound like you have something totally different than what we have happening to us.
You may need to pull the whole control out of the dash and give it a good look over to see if you can find something.
Maybe that leg if I under stand it right works the fan switch part and if it is worn maybe that is the cause?
I have a broken control for my 81 and this weekend I will have to take a closer look at it (if I remember to) to see if I can see something.
Have you checked the wire connections on the resister next to the blower motor?
Dave ----
Fuzz, I was saying years back I experienced the problem you were having and it turned out to be my blend door issue.(Mine if going from off to max AC will not blow out vents I have to go to normal then max AC to blow out vents.)
I lived with that here in the south summer heat for many years( daily
driver) until I had enough! I never knew if it would come out the vents floor or defrost Good luck TR
Fuzz, I was saying years back I experienced the problem you were having and it turned out to be my blend door issue.(Mine if going from off to max AC will not blow out vents I have to go to normal then max AC to blow out vents.)
I lived with that here in the south summer heat for many years( daily
driver) until I had enough! I never knew if it would come out the vents floor or defrost Good luck TR
Other than looking at that leg for wear I don't know what else it could be as everything seams to work other wise. I don't have the dash pad on so I guess now would be the time to look into this
Originally Posted by Black Ford XLT
Weird , I know but haven't touched anything .Trust me ,when I do I will make sure it will be posted as a fix for future searches .TR
I was getting my AC prepped to see what else it would take to get going. I was checking to see if I had 12V at the pressure switch in MAX AC per manual - I did not. Troubleshooting ultimately revealed that the AC compressor tang on my vacuum switch was gone. Regardless of selector position, it would never close and kick on the compressor.
Crazy idea:
Someone has been in there before and plugged the harness in upside down. In essence this would just swap switch contacts so that now the short contact is your compressor and the long contact is your blower. At some vacuum switch position, the small ramp will kill the blower even as the compressor still runs. I was surprised that I couldn’t find anything other than the harness length to prevent this - no shape, tab, offset, or other feature to prevent this. It struck me as odd because it’s rare in the automotive world.
If your blower works in VENT but the compressor clutch isn’t powered, a harness swap is unlikely. I told you that idea was crazy!
If you take it apart, I’ve had good luck placing a spring clamp on one side of the spring near the lever stem and gently prying 3-4 of the spring nut teeth up enough so the nut loosens. On the way back I use a socket over the spring nut to drive it back onto the lever stem.
Unless the bottom wings are some sort of plug pilot, I can’t recall another feature to prevent rolling the connector 180 degrees.
Now you have me going to look mine over as I had EVERYTHING apart moving from 1 truck (AC) to the other AC (non AC) to make it AC.
I did see the AC wiring harness is an add on to the factory harness.
I guess besides looking that plug over I should jump out the PSI switch and put my system in AC & max AC to see if I get power out to the compressor wire.
My system is still apart, no compressor or hoses, but best to test now than when I am or a shop is trying to charge it.
Dave ----
Now you have me going to look mine over as I had EVERYTHING apart moving from 1 truck (AC) to the other AC (non AC) to make it AC.
I did see the AC wiring harness is an add on to the factory harness.
I guess besides looking that plug over I should jump out the PSI switch and put my system in AC & max AC to see if I get power out to the compressor wire.
My system is still apart, no compressor or hoses, but best to test now than when I am or a shop is trying to charge it.
Dave ----
I vacuumed tested my unit on the bench by applying vacuum to the inlet port and capping all ports but the one that should be applying vacuum to its vacuum motor and seeing if it sucked air in. It's a repetitive process since most positions send vacuum to multiple motors, but helped confirm vacuum was going to the right places in the right vent selector positions. Unfortunately, I did not continuity check the vacuum electrical switch through all its positions, so it was halfway back in the dash before I realized I had a problem with no 12V to the AC pressure switch. I really only got to looking because the PO ran a wire direct from the AC compressor clutch through a 30A fuse and SPST toggle switch. It wasn't powered, but I assume he/she was going to essentially hardwire the compressor clutch through a switch. I also noticed the pressure switch output to the compressor clutch was cut off at the harness. Got to love hack jobs.
For removal, I fought with attempting to disconnect the electrical harnesses with the unit essentially still in place, which was a disaster. I then read where it's easiest to pull the ashtray, remove the floor ducting (two 1/4" head screws), remove the control head *****, and then push the unit back toward the firewall and pull it out from underneath the dash. There's still not a ton of room, but it is easier to disconnect the wiring harnesses that way. I did have to loosen the temperature control cable off the unit before pushing it back as it's too rigid. There's one spring nut on the stem the cable wraps around and one screw (another 1/4" head IIRC) that secures what's essentially a cable clamp to the control head. That screw head generally faces at a 45 between floor and firewall so get your contortionist on.
Last edited by packagerjr; Jul 9, 2019 at 08:12 AM.
Reason: errors
I don't have a radio, dash pad top, glove box or any of the bezels in place so all is easy to get to.
I just never thought to jump the psi switch put the control in AC & max AC to see if I had power on the compressor wire.
Dave - - - -
Update ,finally took my AC controls out of the dash, as my Max-ac position quit altogether. I could not manipulate the slide switch to make it work any longer. (Few years back I had replaced my blower switch as it looked burned .) The same has happened to my temperature blend door lever switch.Kr98664 had the same problem(above) as I wanted to check before I ordered this switch. The listing on the switch is motorcraft #E1AH-19D961-BA OR motorcraft YH380 . The prongs are burned along with the body of the plastic .This is not the fan switch as some retailers have it advertised .Others have it listed as heater control switch or damper door switch..i shall post pictures or this switch soon Thanks TR
This is not a very common failure in these trucks, so you should be able to find a good one in the junkyard. Here is a list of junkyards in South Carolina that say they have one.
Dave, in the last picture (last thread)the 2 screws hold the part Motorcraft #YH380 ,that I need .I found that part on eBay ,but the connector that slides in to this part is also burned.perhaps I may find the connector at one of these bone yards.(it’s part of the wiring harnes)
The yh380 is actually a switch that has 4 metal prongs and (it uses a slide hooked into the back - from the actual control slide) and apparently it control the vacuum along with fan etcc .. I am still learning and this is a lesson . Two of the yards you posted I have been at and I am glad to know I can also get a controller if needed ,Thanks a ton TR
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fan on HIGH ) switch from max to defrost several times(back forth) to get max operating correct . And yes in vent the fan operates .As stated before when I put it in max I actually hear the compressor kick on(as in norm).but no fan ,swap it to norm fan acts as it should( usually on high) .Oh and a few times I have had it in max WHILE traveling down a rough dirt road it will quit .I did not mean to confuse any one with the blend door issue that I experienced a few years back Thanks TR
