Well I just noticed this after trying to get heat throught the vents on my truck. My hands got cold one day & I changed the vent setting to "VENT", nothing happened, air still blew through the DEFROST vents, then I switched it to FLOOR because my feet were cold, & it STILL blew out the defrost vents.

What can I do to fix this?
I am sick of driving around with gloves on!

I just picked up a 91' F350 & the vents all work just fine, so it isn't operator error

Thanks.

Garrett

 

Trace the vacuum line from the little plastic manifold screwed to the firewall above the R exhaust manifold over to the R hood hinge area, and the branch to the reservoir glued to the evaporator cover. Sounds like you have a leak somewhere. Try routing a new line straight off the manifold to the one going into the fan housing to see if that eliminates the leak.

 

my '89 is doing the same thing ...when I move the selctor there is no resistence...( i dont know if there should be ) it seems to me that the cable is broken ( if there is a cable) the vacume motor works ...I would check yours ..I dont know what else there is to check ..I would do what Steve says and replace the lines..

 

I'm going a bit nutso with a similar problem. My heater was sometimes on, sometimes not. Blower is always working when I turn it on regardless of heat. The core itself is hot, but cold air blows from around it into the truck. I replaced the thermostat last week, thinking it was the problem. When I reach into the housing I.e., into the glove box and to the left, I can feel a door there that opens and closes when the control is turned to AC or Vent area. It opens when turned to heat. Any ideas? Once again, thanks

 

chas1234
If you have an "A/C" button with a blue light in it, your system is totally cable-operated, except the "Max A/C" (fresh/recirc) function which is vacuum. That's '87-?89 only.

On all others with A/C, everything is vacuum-operated except the temperature which is cable.

 

Steve what should we look for (I dont have any AC by the way) again mine is stuck too and it would be nice to have the heater system (I am sure 3006rocks) wants to know too...

 

When i bought my 94 the selector didn't work. The guy had a pice of rope tied to the door to pull the door open to change were the heat went. Under the hood i found directly behind the plenum on the pass side there was a t- fitting one line to engine, one to the vacume selector on the heater box and a broken end. I found the broken plastic hose fliped up under the plenum behind the strut that superts the plenum. If im not mistaken the hose is red. I just riped out the 1/2" that was snaped off in the t-fitting and slid the hidding tube in and wraped it with electrical tape. have had no problems since.

 

I don't know enough about the heat-only systems to tell you anything specific, but just trace the control (cable or vacuum line) that doesn't work; all the way to the intake manifold if necessary. It's not an electronic system, so you'll be able to see whatever's messed up if you dig deep enough.

 

Check the connections to the vacuum reservoir which is probably mounted on the passenger side fender, behind the air pump. Good luck!

 

On '87-96, the "coffee can" reservoir on the R wheelwell is ONLY for the EGR & smog pump valves. The one for the ventilation system is glued to the side of the evaporator housing facing the R exhaust manifold inside some silver insulation.

On '80-86, the spherical plastic reservoir on the R wheelwell is for the ventilation.

 

My 1990 F150 (302) doesn't have a spherical vacuum reservoir attached to the evaporator cover, I'm not saying it never had one but it certainly doesn't any more. My ventilation controls receive their vacuum source from the "coffee can" on the passenger fender. It might be worth checking out the other vacuum containers (especially the one behind the smog pump) in case someone has tapped-in to one of them for an alternative vacuum source. Just a thought.

 

truckfan
Reread my post: the spherical reservoir is '80-86. Yours uses the one glued to the evaporator cover for the ventilation system and the coffee can for the EGR, TAB, & TAD.

 

My '86 Bronco is only blowing out the vents. No resistance from the selector switch. Should there be cable hooked to this or is it totally vacuum controlled? It has A/C, but is currently non-functional.

 

On our 1982 Ford E150 351W V8, it will not blow heat and air will only come out on defrost.
Previous owner messed up with the vacuum hoses. I've traced all the vacuum line hoses going to the Air vent, heat/cold controls. I found two very small vacuum lines at the upper center of the firewall (looking at the engine in front). One of the small vacuum lines was broken and I just put a plug in it. The other small vacuum line is connected to a T-fitting. One end of the T-fitting is connected to a small plastic reservoir and one end of the T-fitting has hose but not connected to anything. What I did was connected that unconnected hose with a T-fitting to the cruise-control vacuum hose source.
It worked after that. We have now cold/heat, selector for defrost, lower vent, front vent.

 

I think maybe its your selector motor. (couldent be really positive) having the same problem i can change my vent to blow cold or hot air or what speed i want it to come out but cant change off of defroster. There is a control motor back in the dash it would require taking the dash out but i think if you change that you'll be free to select the output.