AC not blowing hard

[Steve A]

X2

With the A/C off can you get the fan to blow down at your feet without the defrost blowing, can you switch to defrost and no air at your feet? Can you switch to vent and shut off the other 2? I'm guessing you can't shut off the defrost. I too don't know where the hell those doors are, someone else will have to chime in.

Sounds like 2 different problems. Check that vacuum is available at the control panel and from there to the blend door actuators. As for the blower motor not blowing hard, check the wiring to the speed resistor mounted on top of the air box behind the glove box.

 

[PlayingWithTBI]

Check that vacuum is available at the control panel and from there to the blend door actuators.

What year truck is this? My 88 doesn't have vacuum controls - all electric.

 

[wrenchjockey23]

I have the same problem. I have a 98, so some may be different. ( older had vacuum?) I found the electric mode actuator works fine it’s just that one of the rods has popped off at the box. This is located at the drivers side of the heater box assembly and can be seen by crawling under drivers side dash and looking up and forward. Kinda near the accel pedal stuff etc. The linkage rod and it’s central cushioning spring is still there, just not connected at the box. I realized the “ lever” that the linkage connects to was not sticking out of the box. Hoping it had simply fallen off I found the linkages ( the mode actuator has two ) and they each came with their “lever”. I found these on Amazon lol. However, the lever just slides in the hole in the box and does not connect to the flap inside. I’m guessing it’s time to take the dash out to find out why the flap ( door ) has fallen into the box. This condition allows some blend door action on one rod but doesn’t move the further most forward door ( defrost vent). Yeah, with the right conditions it frosts the left side at the wiper area and is difficult to manAge while driving. For now, I lay something up there to block the air from hitting the windshield. Hope that helps. Oh, the linkage number for the front defrost door is # 52487132 . Also, if anyone has gone further than I have any advice is appreciated. I have toyed with cutting the side of the box to access but not sure I want to butcher this up. Oh well, soon I’ll likely pull dash. I just diagnosed this last week.

 

[achevyman1956]

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[achevyman1956]

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The second arm is definitely connected to another door. This box is a spare I took off a Tahoe today


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[east302]

I’d suggest replacing the doors while you have it apart. The rubber on the lowest door of mine rotted, so it leaked air through the floor vent. The foam on top of the case can be replaced as well, if it’s like mine it’s probably crumbling and going to leak air.

Also, take a look at the foam border on the evaporator coil, it should prevent air from bypassing the coil when the case is closed up. Mine didn’t, so I used weatherstripping to build it back up. If you’re replacing the coil, and you might as well, the water screen on the downstream side is just glued on.

The crushed fins are from my over-aggressive cleaning over the years, apparently, so heads up to anyone else.

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I’ve hated the a/c in this truck for ten years. Air flow was like a mouse fart and it never cooled very well. After replacing everything in it, it works awesome now.


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[Schurkey]

That foam is evil. The foam on my truck deteriorated into jelly and dust. Could not warm the cab in the winter because the foam seal between the metal of the cowl and the plastic of the air box/HVAC blower case had rotted out. There was more cold air blowing past the seal than there was hot air coming out of the heater duct.

Tore the dash apart, replaced all the foam I saw (it was all rotted--gooey and falling apart--with strips from a roll of home weatherstripping foam, and when it was back together, I had to turn the heat down because I was roasting in there.

 

[achevyman1956]

That foam is evil. The foam on my truck deteriorated into jelly and dust. Could not warm the cab in the winter because the foam seal between the metal of the cowl and the plastic of the air box/HVAC blower case had rotted out. There was more cold air blowing past the seal than there was hot air coming out of the heater duct.

Tore the dash apart, replaced all the foam I saw (it was all rotted--gooey and falling apart--with strips from a roll of home weatherstripping foam, and when it was back together, I had to turn the heat down because I was roasting in there.

What exactly kind of weatherstripping did you end up using? the box is actually fairly simple to take apart. Its just the process of getting to it.

 

[scott_williams2]

Ok y’all sorry for the late reply but the new blend door actuator definitely helped. It blows noticeably harder and it actually switches air to differnt vents on their settings as it should now although the defroster still blows 24/7. It’s not as good as I’d like it blow but i understand it is a 20 year old truck. I’ll try some of yalls suggestions to make it better thanks!!!

 

[Schurkey]

What exactly kind of weatherstripping did you end up using?

I bought a roll (or two) of generic closed-cell foam-with-applied adhesive.

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But I don't remember what thickness I used. Perhaps 1/8", perhaps 1/4". I guess it would be easy enough to look at the existing foam to judge it's original thickness, then buy replacement foam to match.