Heater problem, not much air blowing out

[93fordturbo]

My truck has decent heat, and supposedly a/c, but I can't switch from vent to defrost to floor, and the air that does come out isn't fast at all. It seems slower than what the low setting would be. It has a new blower motor, any ideas? It seems like it pushes air a tiny bit faster after it runs a while, but I could be wrong.

 

[IDIoit]

check the vacuum lines, sounds like the blend doors are not workin right.

can also jump the blower motor wires to 12V to see if its the switch?

 

[93fordturbo]

Seems like the vacuum is good, how much vacuum should I have. What wires do I jump now?

 

[IDIoit]

just the blower motor wires.
i havnt looked at my blower motor in some time, but there has to be 2 wires that lead directly to the motor itself.
possibly remove the blower motor completely and bench test it.
could be something simple as the bird cage spot welds broke and its not flowing air.
while youre there, you can inspect for birds/rats nest in the cowl

 

[crash-harris]

There is a white vacuum line that runs to the valve that is visible on top of the ductwork underhood, tucked near the passenger fender. The line is notorious for degrading and basically turning to powder.

As for the fan speed, there is a resistor unit in the ductwork in the area under the glovebox, maybe a little closer to the center of the dash. It uses different resistors for different speeds, so pull it and see if any of the resistor coils are burnt. I had this problem with Bruiser when I first got her and the resistor unit turned out to be the issue with the fan speed.

 

[IDIoit]

There is a white vacuum line that runs to the valve that is visible on top of the ductwork underhood, tucked near the passenger fender. The line is notorious for degrading and basically turning to powder.

As for the fan speed, there is a resistor unit in the ductwork in the area under the glovebox, maybe a little closer to the center of the dash. It uses different resistors for different speeds, so pull it and see if any of the resistor coils are burnt. I had this problem with Bruiser when I first got her and the resistor unit turned out to be the issue with the fan speed.

note:
dont know much about the OBS, except for the fact that the brick nose has less vacuum crap.
not saying this couldnt be the issue, but he does own a OBS

 

[crash-harris]

There's a good point. @93fordturbo are we discussing the '93 or the '85?

I'm also not as versed with the OBS configurations. The Bronoc we have here is an OBS, but seeing as how we decided to nix the project, I haven't eyeballed the little differences between it and my bricknose trucks. IIRC, that vacuum line is there from 80-96/7. The resistor units are slightly different between bullnose, bricknose and OBS...I think, so don't quote me on that.

 

[mblaney]

The symptom for the resistor fault is the fan will only work on the highest (no resistor) fan speed. Resistor network can sometimes be salvaged by fixing corroded connections.

Pull blower motor and spin the squirrel cage by hand; tight? take it apart and lube it up. You should also be able to hear the blower fan at the different speeds; chances are that if the motor is tight the lowest speed setting won't even spin it.

 

[93fordturbo]

It is the 85. The blower motor is only a couple months old. And when key is on, but engine is off, I can hear different speeds. Just isn't forcing much air

 

[crash-harris]

Mine burnt out the middle 2 speeds. Ultra low and high only. IIRC Autozone is now stocking the resistor units. When I did mine I had to find a good one in the junkyard. I looked up A LOT of parts for 80-91 Ford trucks when I worked for AZ