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Heater / A/C Damper Doors

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bmooredeer

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Hi CK5 Community!

I have 89 Jimmy and have been experiencing some issues with the heater and blower motor.......long story short I replaced the blower motor 4 times in the last month. Original replacement was dead out of the box, second motor worked for a week, and 3rd replacement was dead out of the box - 4th time the charm?

The first three motors were all the same model/brand/serial numbers which I'm assuming were on the same shipment from China - 4th was from Napa and a bit different.

Now that I have the 4th motor installed and running there is no air blowing from the vents but the motor is pushing air on all 4 speeds. I removed the glovebox and duct behind it which got me into the bowels of the dash. There are two damper doors in the dash-
***The door connected to the hot/cold lever on the dash assembly seems to work great and controls the damper door set farther back closer to the blower motor and heater core.

***The door directly behind the duct I removed inside the glove box (some post refer to this as the "mode" door) seems to not be working correctly. There is a little white piece of plastic that is broken on this door which I will replace (saw this on some other threads) but my bigger question is-

What controls this mode door? It doesn't appear to me that fixing this broken plastic piece will correct the problem - should there be some sort of linkage from the actuator above this door to the other "damper" door cable??

Is this vacuum controlled? One item to note, when I replaced the blower motor there is a small cooling tube about 4 inches long that would not reach the outlet on the new motor so I plugged it - as a check with the heater running on high I connected a small vacuum to where this went into the heater duct and it did not make the air blow any harder.

Sorry for the long message - this is my first post here and I'm hoping to get this fixed once and for all!!! Thank you!
 
The mode door is driven by vacuum. I don't remember exactly how it's set up, but there is a vac can on top of the duct work. It's possible a vacuum line is cracked or just pulled loose. I don't know how the doors would get positioned to block all airflow. Are you sure the inlet to the blower isn't blocked? Most have a fresh/recirc flapper near the passenger foowell that is vacuum driven. Otherwise air comes from the cowl area, which could be covered with snow and ice this time of year.

The little hose on the blower motor is to cool the motor windings. If your new motor isn't set up for that, you can only assume that it doesn't need it.
 
Somewhere on here I think, there was talk about replacing that little plastic piece. Apparently not your only problem, but if it is, the post should be here somewhere.

If the motor has a vent on it, really need to try and get it hooked up. It will take some time (depending on conditions, how often you use it, etc) but eventually dust getting into it will cause issues.
 
dyeager535 said:
If the motor has a vent on it, really need to try and get it hooked up. It will take some time (depending on conditions, how often you use it, etc) but eventually dust getting into it will cause issues.
Click to expand...
I took his description as no vent hole on the aftermarket motor. So the only thing to do is block the opening in the plenum.
 
Blue85 said:
I took his description as no vent hole on the aftermarket motor. So the only thing to do is block the opening in the plenum.
Click to expand...

"when I replaced the blower motor there is a small cooling tube about 4 inches long that would not reach the outlet on the new motor"

I guess the OP will have to fill us in. Outlet on the new motor led me to believe there is a hole, but that the motor itself was clocked wrong.

No idea if cars used the exact same motor, or if it was "clocked" differently. Mechanically and at least at a casual glance externally, they are the same motors.
 
Thank you for all the replies! In regard to the damper door I've ordered a new plastic piece and had my mechanic take a look at the vacuum system, they found a "pinched" line that will hopefully correct the issue.

On the blower motor the hole is "clocked" differently as described below, I've plugged the motor hole as well as the plenum hole. From my understanding the cooling provided by the hose from the plenum is very minimal and not essential - is this best left open with a longer re-routed hose?
 
Maybe you can clock the motor differenty relative to the mounting plate to line up the hole? Or maybe you can swap the motor onto the mounting plate you took off?
 
I'd run it. GM never installed/designed something that wasn't necessary. If it cost them $.02 for every vehicle, they cared.

Not saying it will fail due to that, just that it's there for a reason, and wouldn't be had they not found that issue. Since it's on all the AC equipped rigs AND heavy duty heater optioned trucks, it has to do with the motor...the only way to make them spin faster in the same package is change the motor windings, which must increase heat and eventually lead to failure/problems.
 
Hold your hand against that motor after it has ran for a while and feel how hot it gets. It's needed.

Martin
 
Thank you for all of the updates! I replaced the white plastic clip and the motor was still not pushing air - turns out that I had a counter-clockwise motor. I replaced the motor with a clockwise unit, the cooling tube has been realigned and everything is working great.
 
Bringing this back from dead similar problem will bring vacuum pump home tomorrow and test door and line for vacuum.
 
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