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Thread: A/C irratic function
10-14-2012, 06:11 PM #1
A/C irratic function
i have a 1990 k1500 4x4 with 5.7 engine.
sometimes, in the past, with the a/c on, it would blow about 50% out of the vents, and the other 50% either out of the dash or down by the trans tunnel. i would hit on the lower unit, and the (flap) would close and it would them blow 100% out of the vents.
but now its doing something different. its blowing about 25% out of the vents, and i can hear the blower blowing, like deep inside somewhere, but nothing is coming out from the trans tunnel vent or the defrost..
what is going on here ? anyone have this happen to them before ? cant figure this new problem out.
10-14-2012, 07:01 PM #2
The air is diverted using doors (mode doors), you may have one sticking.
The newer trucks use electric motors, before that, the motors were operated by vacuum, I don't know when they changed over
Try searching the site for mode doorsRay
'09 Avalanche LTZ - Black
'05 Envoy XL (sold)
10-15-2012, 03:08 AM #3
thanks much.. i will search for "mode doors", when i get home from work..
10-15-2012, 11:00 PM #4
I've done both the passenger and driver's side actuator replacements on my 2004. Sadly I have no clue if that knowledge translates/transfers to a 1990 K1500. :(
10-16-2012, 03:12 AM #5
after searching on here and the internet, yes, it seems as if the mode door actuator is my problem.... it really only pops up every few months or so, but i think i will replace it anyways, since it is so easy to access....
10-21-2012, 03:06 PM #6
ok guys, it was good all week, and acted up today again.
earlier in the week, i marked the actuator thats over the trans tunnel, on the left side of the box. i marked it when it was all working fine, blowing 100% out of only the vents.
today when it was acting up, blowing less than 50% out of the vents, but nothing out of the defrost or lower trans tunnel opening, for the heat, i looked at my marks and that actuator is opening in the same position as when it was working fine, so it cant be that actuator.
i found a drawing and see there is a "temperature actuator" thats located in the middle of the unit. could that be my problem ?
on that drawing it does not show a right side actuator, mounted right next the the blower motor, on the passengers side...
what does that actuator do ? again, my drawing i found online doesnt show that actuator.
the cooling system is working fine, dripping a lot of condensed water through the drain tube and onto the ground.
its driving me crazy....... please help.
10-21-2012, 06:01 PM #7
I wish I knew how to help you, but my knowledge is limited to the 99-06 (and 07 classic) years, as that's what I own and have worked on. :(
10-21-2012, 06:02 PM #8
10-22-2012, 05:21 PM #9
i laid up under the passengers side dash today and that actuator really looks like a pain to change out. no room to get at the screws. i have marked the position its at when its working correctly, so next time it acts up, i will see where the shaft is in relation to my mark.
also i figured out that the next time it does act up, i will try cycling it through the three positions of defrost, vents, and lower trans tunnel vent, to see it i can "un-stick" it and get it blowing through only the vents.
just dont want to change it out, since its so hard to get to.
10-22-2012, 08:30 PM #10
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