New member here. 86 Bronco, with heater and A/C. The dashboard vents and the floor vents both push air all the time, in heat or A/C mode. The vacuum motor up under the dash is working, the flat pushrod is going back and forth but whatever it's connected to isn't doing much if anything. Plenty of vacuum. Does this sound like the little deflector door hinge has failed? Do I really need to remove the dashboard and plenum to fix? Think I might just learn to live with it,

 

I'm not sure if I understand, but I will mention that the only time the doors are closed and the fan is off is when the slide control is set to off. NOT THE FAN CONTROL! I dont like the fumes when going through a tunnel. I use to turn the fan control to its lowest setting when I entered a tunnel thinking that was off. But that just slows the fan. If you are at highway speeds, it hardly makes a differnce. (the air is forced in.) You must slide the A/C control to off.

 

One other thing. The door is sprung shut. The vacume holds it open. Usally the complant is the door shuts when you want it open. (weak or leaking vacume) Yours may have a broken spring.

 

Welcome to FTE

There are three vacuum motors on 1980/86 F100/350's & Bronco's with factory installed Integral A/C.

D9AZ18A318C .. Vacuum Motor (Motorcraft YH350) / A/C Heat Door / Located on Plenum Chamber, one port.

EOTZ18A318A .. Vacuum Motor (Motorcraft YH362) / Recirculating F/A Door / Located on Evaporator, one port.

EOTZ18A318B .. Vacuum Motor (Motorcraft YH363) / Defroster Door / Located on Plenum Chamber, two ports.

All these vacuum motors are controlled by the following:

E1AZ19B888A .. A/C Vacuum Control Selector Valve Assy (Motorcraft YH360) / Fits: 1983/89 F100/350 & Bronco.

This valve bolts to the backside of the A/C Heater control panel, all the vacuum lines connect to it.

When you slide the levers on the control panel, this valve (is supposed to) open one door and close another.

This valve also has the "kicker" switch mounted to it that turns the A/C on.

Look at the ends of the rubber vacuum hoses where they attach to the ports on the vacuum motors to see if all are connected.

Plus...the ends of these hoses tend to crack apart due to age.

 

Thanks for the info. My fresh air/recirculate door is working fine. That's accessed from under the hood on the pass. side. near the blower fan.

The problem I'm having seems to be with the one that controls air flow between the dashboard vents and the floor vents. When I slide the control between those settings, there isn't much change from dash to lower outlets, but I can hear movement in the ducts like a door is trying to close or open. Most of the air flows from the dash in either position.

I can see an actuator above and to the right of the transmission hump under the dash. It's moving in and out, and I can hear the door moving, but no change in air flow. So far I haven't spotted the other under dash actuator, I'll look again. I have a couple of manuals for the truck, and in the Haynes I see an illustration of the plenum assembly and vacuum motors, but it's a blown apart shot and I'm not clear on the actual location and orientation of the two under dash motors.

All the vacuum lines seem good at the controller, and no hissing noise under there with the motor running. I'll get back out there and take a closer look for the other actuator.