Hello all,

So I recently had the AC replaced in my truck, which is a 1982 f-100 XL with factory AC. It's blowing cold as ice and I'm super happy with it. But of course, something had to go wrong. I was in the parking lot earlier today and I went to turn the AC from off to MAX/NORM. Which turns the AC on and the air blows through the vents. Well, I heard something snap and there is no longer tension in the handle. There use to be resistance to actuate a door but it seems like that is no longer connected.

Now, when I turn it to MAX/NORM now, the AC Still turns on and defaults to blow on the windshield and floor. It still blows cold. And it turns off as it should. But the air does not blow through the vents anymore. I snooped around behind the dash and everything seems to be in place. The black/blue wire that goes to the air door actuator still has a vacuum, but the actuator doesn't move.

Could it be that the actuator is bad? Or did something come loose that adds vacuum?


Okay guys here what happened. There is a actuator that is spring loaded, that diverts vaccum to and from each like running the air from the blowers to wherever you want them. It fell apart completely. So I was able to salvage one from a junk yard. I got super lucky.


So here we have the switch that broke (without the black selector disc)

Here is the part number.

Here is how I got the damn thing out of the dash. Without this guy I would have been lost. Haha.


I don't believe this is the right part but it looked like this when it was put together.

 

On the control panel, only the upper lever (hot/cold) directly controls anything external. It moves a push/pull cable that moves the heat blend door, over by the glove box.

The lower lever operates a combination electrical/vacuum switch, attached directly behind the face panel. It sounds like either the lever itself has broken, or the switch has failed. On my '84, this combo switch is Motorcraft YH380. Not sure if '82 had the same part number:



https://www.rockauto.com/en/parts/mo...er+switch,4248

 

Awesome. It is the bottom lever. I'm assuming the switch broke. But apparently I can't find any part that is compatible with 1982 f-100. Because for some reason it's different. I'll keep looking though. I appreciate the response. And you've pointed me in the right (hopefully) direction.

 

Does the bottom lever have an OFF position at the far left? If so, does the fan turn on and off properly with movement of the lever? That would indicate the lever mechanism is intact and moving the electrical portion of the combo switch, but something internal has failed on the vacuum side.

Hopefully somebody will chime in with a correct part number for 1982.

 

If it is just the switch, cable, or vacuum actuator/ vac line, you are lucky, just fix and replace. If not, the HVAC diverter door hinge has broken and you need to tear down dash a bit to replace it with a metal piano hinge from home depot. Ask me how I know.

 

Check the vacuum lines that come out of top of the A/C box under the hood. When the system looses vacuum it defaults to the defrost and floor. We had this issue and it ended up a cracked line. They are hard plastic and had broke, we spliced them with some small rubber vacuum line and it corrected the problem. Hope this helps.

 

Hope it is not the hinge and that "snap" is not a good sign but more checking needs to be done.

Yes I would check for vacuum starting at the motor and working your way in.

I had 1 of the 2 plastic lines crack right were it passes thru from engine bay to the cab.
I knew I had a problem because it was working when I drove it into the garage and I did noting in that area.
I was able to check for vacuum, I had vacuum on the bay side but none inside.
There is a clear connector behind the glove box. Motor running pull this apart and see if you have vacuum there if not fix it.
I ran rubber hose thru that bushing between bay & cab and hooked them to what was left of the plastic line inside the cab.

If you do have vacuum at that point I would pull 1 of the lines off a vacuum motor and check for vacuum there by moving the control and checking.
If no vacuum then yes the control is bad. If you do have vacuum recheck that vacuum motor that it is not moving. I believe you can also move the arm the motor moved by hand to see if it is stuck.

That is how I went about checking my system and I had to go from scratch as the PO cut the HVAC control out of the dash and sold it before I got the truck.
Good luck
Dave ----

 

I should also point out I think there are 3 different vacuum control parts for the 80 - 86 trucks
I forget the year break down but IIRC you can run them it just that the displays are a little different or was it the vacuum ports?

I know this as there is a heater hose vacuum valve that can be added to close off hot water to the heater core to help make the AC colder.
One of the ways to hook up the vacuum to turn off the water and have cool air out the vents with out the AC and the other you can not.
On mine you can not so I found out when I went to hook up the valve.
So the valve is off when on MAX AC and that is fine with me. If I find it is to cold and need to add a little heat I move the control to Normal and I can then use the temp control lever.
Dave ----

 

Are you talking about the door for the four vents on the face of the dash, the one with the plastic hinge? I doubt the hinge broke, because when it does the door flops loose inside the plenum and can’t seal off the duct. You’d get air from these vents all the time, but he has described just the opposite.

This actuator is spring loaded to close the door so you get defrost for safety in case of a loss of vacuum. Even if the actuator failed, or vacuum was lost (broken line, etc), I don’t think you’d feel any change in effort at the control lever. However, he did describe a loss of resistance when he moves the lever, as if the innards of the switch are not connected anymore.

 

If it was easy to pull the control, IT IS NOT, then I would say pull it to check.
When mine stopped working I was going to pull it to check and after getting part of the dash apart and not seeing a way it came out I looked to see if the control was getting vacuum and that's when I found the cracked line at the pass thru plug.



Dave ----

 

I am so glad I didn't have to do that haha. explanation in OP.

 

Awesome job on the fix and posting it up. to avoid the below for someone else: