SIXSLUG

I just noticed that cap Sherrifav8r is talking about was quite brittle and cracking pretty badly last time I was underhood on mine. That would be a good place to look for a vac leak and a cheap repair. It sounds like a blend door problem to me. When I had critters in my old Ford it always kicked bedding fibers out the vents and smelled like vermin.

neveragain

I have been having these problems as well. At -43*C the cab was down right cold. Since everyone has checked most of the items. Has anyone measured the voltage to the fan motor. Someone put a multi-meter on DC Volts and measure the voltage to the fan on different settings please? My suspiction is that the control (three *****) the contacts are heated you may find that if you take it apart some or all of the copper buss is some what blue. This will cause a voltage drop before the fan so less air flow. Too cold here to do that yet. -5*c for a high. Were is spring???

rriddy

I checked the vacuum lines, and found one cracked. So I replaced it all the way to the hvac box. Still same flow. It honestly sounds like it is flowing out of somewhere in the fan area, but for the life of me I cant see or feel it. Maybe a blend door? I just had the whole box out and apart and there was nothing in there(vermin orthe like) I'm at a loss on this. The intake side was all clean as well. The fan motor and cage are new. This thing spins like a prop plane. It should be blowing me out of the seat. I'm almost to the point of putting in a whole new box.

Thundercraft

I hope you find a really obvious reason because I too have the same complaint.

When it was really cold, I was very thankful for the bum warmers.

I know that there is good flow going through the cores, as there is a good amount of water coming from the evaporator. (I almost always have it on mixed floor/defrost to keep the windows from fogging up).

Stamey

I was going to ask if the fan sounded like ti was blowing as loudly as your Dad's truck, but I guess you've already answered that.
The next thing I'd be tempted to try, and I'm not even sure how I'd accomplish it at this point, but would be to get some sort of smoke into the system, likely through the cowl, to see where it comes out. I don't know that there is a "smoke" that would be pleasant to flood your truck interior with. Even as much as I like that black smoke from my tailpipe I don't want it inside the cab.
Anyway, are you sure you have vacuum inside the cab? It might sound stupid, but I found the vacuum line on my 96 plugged up with some kind of plastic (I have no idea what it was or where it came from) and I was getting no vacuum inside.
To test this you may have to pull the selector switch out of the dash to see that vacuum is getting all the way to it, then you can check the outputs from it and see if vacuum is being transferred through the vacuum switch to the various actuators that operate the doors.
The sloest actuator you can check, if memory serves, would be above the accelerator pedal on the end of the HVAC box. It is for the dash vents. If it is getting vaccum it tells you that vacuum is getting all the way into, and through, the vacuum switch in the dash. This could be done before you pull the switch out of the dash.

Chris

rriddy

Yeah I thought I was finally on to something with the vacuum lines, but still the same. I have vacuum in the cab, I can watch all the traps open and shut according to where the selector is. What is the possibility of the blend door? I'm grabbing at straws, but I really can't think of anything else. It really sounds like it is flowing up till the evap/heatercore/blend door area. I'm thinking at this point I'm going to pull the box out and put it on the bench and operate it with a few dc supplies and a vacuum pump and see if it's in the box or what.

Busboy

Hi all, the blend door doesn't block air, it's between the evaporator and the heater core. All air goes through the evaporator and the blend door directs air either straight into the duct work or through the heater core or a combination of the two. Have you checked the vacuum actuator on the drivers underside that has two vacuum lines on it? Red on the end and BROWN on the side. The actuator is the "Heat/defrost" actuator. Make sure the vacuum lines are hooked up correctly and check both vacuum ports with a vacuum pump to see if you have a partially leaking actuator.

Have you by chance changed the rotary vacuum sw in the dash? They may look the same but they operate differently. I am assuming the fan turns the correct way? A fan running the wrong direction will give lots of noise but next to no air flow.

Good luck for now, I gotta go fix the rad and the AC on a ricer that took a bunch of debris through the front on the highway, what a mess .

xtoyz17

Busboy, I don't directly need help but have a few questions you may be able to answer since I foresee others asking the same thing.

1) ***** are different how? Year to year? Different body styles?

2) What sort of vacuum is the actuator expected to hold?

3) Don't you know better than to help ricers?

Junkdude

The fan motor could have been made wrong and is blowing backwards. Can you reverse the polarity and see if that makes a difference.

Busboy

xtoyz17, (1) the ***** are the same it's the vacuum sw that are different internally from an AC to a NON AC. They look the same and the vacuum fitting fits but are ported differently. (2) the vacuum actuator should not bleed off any vacuum as it is a sealed chamber. (3) the ricers are mine that my wife and kids drive so I kinda gotta fix em.

rriddy

OK guys, I finally got it. The fan was in fact blowing backwards. But to my surprise i plugged the factory fan back in and the factory wiring was reversed. That explains why it was always so low, I guess I never really noticed it for some reason. After switching the wires this thing will blow you out of the truck on two. Very nice to have sweaty feet instead of frostbite. I kind of feel silly for not trying that earlier. But, I do have the dash removal down to a science. Thanks for all of your guys help, now I can start my adrenaline install.

Stamey

HOLY SMOKES!!!!
That's unbelievable. Never heard of that happening before.
Glad you finally found it because it sure never crossed my mind.

Chris

Busboy

Glad you found it...Some fan motors actually have a jumper that you have to connect either one way or the other to get the correct motor direction. Not factory but aftermarket.