HVAC fan weak?

[great white]

My 98 has had (what I would call) very poor HVAC fan performance since I purchased it.

My 89 would damn near blow you toupee off, but my 98 has barely more than a popcorn fart at full blast.

first, is this normal for the newer style dash? The blower just can't seen to provide much air. I can hear the fan working it's butt off down under the dash though.

I beleive (if the manual schematic is right) all the air has to pass through the AC evaporator before it enter the rest of the plenum, be it AC or Heat selected.

If so, is it possible that my evap has been mostly clogged by debris?

I do know that I'm constantly pulling leaves and tree droppings out of cracks and crevices on this truck.

Anyone ever experience that problem?

maybe I'll see about dropping the dash today and have a look.


I just can't believe the fan output is this weak....

 

[WarWagon]

Check the connectors at the blower motor and the pesky connection above it for burn out. Blower motor may be spinning slow due to worn brushes or binding bearings.

Pull the blower motor and check the evaporator. Then vacuum it with a shop vac and brush and or small extension wand. Best to just cut the shop vac hose or disassemble it. Then use the hose end to get the dirt piled up on the bottom.

Next you use scrubbing bubbles and a garden sprayer with a towel on the floor below the HVAC unit drain pan. Try and not flood the drain pan too often. Use a small nylon brush to clean the surface of dirt if it is really bad. Construction or farm off road vehicles are this bad.

The recurc door can give you trouble staying in outside air or being forced to outside air due to a weak door position motor unit.

 

[great white]

Check the connectors at the blower motor and the pesky connection above it for burn out. Blower motor may be spinning slow due to worn brushes or binding bearings.

Pull the blower motor and check the evaporator. Then vacuum it with a shop vac and brush and or small extension wand. Best to just cut the shop vac hose or disassemble it. Then use the hose end to get the dirt piled up on the bottom.

Next you use scrubbing bubbles and a garden sprayer with a towel on the floor below the HVAC unit drain pan. Try and not flood the drain pan too often. Use a small nylon brush to clean the surface of dirt if it is really bad. Construction or farm off road vehicles are this bad.

The recurc door can give you trouble staying in outside air or being forced to outside air due to a weak door position motor unit.

true enough.

My recirc door is failed in the outside air position.

I don't think it's effecting much as that's where I would want it anyways. I don't use "max ac".

 

[diesel65]

The fan should have some force, more than likely the evap is covered with debris. As warwagon said pull the fan motor.

 

[WarWagon]

Max AC can come on wanted or not and blow your hat off if the AC pressure gets high enough on some models.

 

[iamdave0887]

I know when i bought my blazer the blower motor was very slow. I thought it just needed a little re-greasing after sitting so long until i opened it up. One of the brushes was non-existent and the wire that is supposed to be attached to the brush was sitting against the commutator. It did spin, but very slowly.

It was cheaper to buy a new blower motor and transfer the squirrel cage wheel to it from the old one, than it was to attempt to fix the old one.

 

[great white]

My fan spins just fine guys.

It can be heard jamming away down in the dash and responds fine to switch selection.

I need to get in there and see what's hanging around.

Wouldn't surprise me to find a near solid mat of crap in there.......

 

[great white]

found my problem:

Pulled out the Fan motor and stuck my hand in the plenum.

I couldn't even feel the evaporator fins.

All I could feel was a thick furry mat!

Sure enough, the core was plugged solid with dog fur. It had to be 1/8" thick chocolate lab fur. Sheesh.

There was no chance it was coming out with the vacuum either, it was packed in with dust and dirt and deep into the core. I pulled out the resistor module and tried to blow compressed air back through the core.

Spent the rest of the dash doing the dash flip and tearing apart the HVAC box. I ended up pulling the fan box off the main hvac plenum and pulling the fur out with a dental pick.

Fun Fun Fun......:rolleyes5:

 

[great white]

All right, new question (well, questionS):

The dog fur mat is gone and there's decent air flow, but the core is still very dirty and it occasionally blows a puff of dust as it comes loose.

Anyone see a problem in shoving a garden hose in the duct and washing out the core?

The duct drain works fine (ac water drains fine).

If I keep the flow reasonable and a tray over the carpet things should rinse out just fine, right?

Anyone ever try it? Any cleaners you've used with a water flush?

*edit*

Hmm, reading up my own thread it seems warwagon has a bit of experience with this.....

 

[WarWagon]

Short blasts with the hose so the drain can keep up... And this is from the blower motor side.

You may want to pull the plastic air intake grill from below the wipers between the hood and windshield and check out what is in there. Also there are two drains for this. One is behind the coolant bottle held in with 1 screw. The other is on the driver's side. Just a plastic part with a flapper on it that can plug with pine needles etc. This drains the area below the wipers. Grease the wiper pivots and replace the washer hoses while you are there.