'94 Sierra K2500 HVAC Issues

[cc333]

I'm not exactly sure what happened, but when I was running the truck the other day, the windshield was fogged up, so I tried turning on the HVAC to defrost it. Well, the blower came on, but the airflow seemed to get stuck somewhere in between the blower and the defrost vent, meaning no air was coming out of any vent that I could find.

Eventually, as the truck warmed up, it unstuck and the defrost mode began to work properly.

However, the panel vents still wouldn't engage. I got floor and defrost, and hot/cold, but no panel vents. Why is this?

My guess is that maybe the blender door got stuck and the actuator's old and brittle plastic gears blew up, but I don't know for sure. Is it easy to fix? Is the appropriate part still available? Is it possible that it's simply stuck, and warmer weather will allow it to unstick??

Thanks,

c

 

[cc333]

OK, this problem seems to have fixed itself for now.

c

 

[Eveready]

I hold my breath every time I cycle the HVAC functions on mine which is a '93. Thus far (pause to knock on wood) everything works. Likely "old and brittle " covers it. I hope someone will chime in here who has gone through the steps to fix one. It would seem to me that someone could make some bucks by building a rebuild kit for the internals of the HVAC systems on these trucks.

It all goes back to GM building a far better truck than they expected. They expected these trucks to last past one primary buyer (3 years to pay it off and buy another) and possibly one secondary buyer who would wear it the rest of the way out for such uses as ferrying lawn equipment and farm use. None of the long range planning included the truck being in daily or weekly use twenty eight years later for yours and twenty nine to date for mine. The small internal parts were not planned or expected to have that long of a service life.

 

[cc333]

It all goes back to GM building a far better truck than they expected.

Indeed! Where I'm at in the SF Bay Area, I see at least one or two GMT400 trucks everywhere I go, so they're definitely very sturdy and long lived it seems!

It would seem to me that someone could make some bucks by building a rebuild kit for the internals of the HVAC systems on these trucks.

Yes, and if that same someone could come up with a foam seal kit for 97-2002 Ford F-150s, that would probably be fairly popular too (we also have a '97 F-150, and the HVAC system, while it works, is very leaky because all the foam seals have crumbled, leading to somewhat weak output and obnoxious whistling when all but one of the vents are closed).

I hold my breath every time I cycle the HVAC functions on mine which is a '93. Thus far (pause to knock on wood) everything works.

I don't give it a lot of thought (I use it like I would a new car), but I do get concerned when I hear weird pops and creaks when I shouldn't. So far it's been fine aside from my earlier mishap (the subject of this thread), but it seems like the actuators will inevitably succumb to the old and brittle plastic gears, especially if used a lot in cold weather (it seems like when it's warmer, the plastic *should* be somewhat more pliable, and thus less likely to break, but when things get this old, who knows what will happen).

We're just going to keep babying this truck along until we can't (which will hopefully be a LONG time from now). I mean, for the kind of money these trucks are going for nowadays ($75k-$100k), one can almost buy a (very) small house or apartment!

c

 

[someotherguy]

Cleaning and re-lubing the slider mechanisms on the vent position actuator has been covered quite a bit and is the most likely suspect area.

Richard

 

[cc333]

Two years, wow!

Anyway, I'm reviving this thread to say that the HVAC is stuck again, and this time it seems permanent.

It will cycle between defrost and floor, but won't go to the panel vents, so it seems that it's actually partly stuck.

Is it new actuator time?

c

 

[ckylec]

I'm having the exact same issue in my 96 Suburban

 

[GoToGuy]

Try to start with , year, make, model, eng. So we know what you got. Is your climate control manual or electric w/ac ?

 

[cc333]

Try to start with , year, make, model, eng. So we know what you got. Is your climate control manual or electric w/ac ?

Well, mine's probably posted upthread, but for clarity and to serve as a reminder, my truck is a 94 GMC Sierra K2500 with 454, electric controls and A/C.

c

 

[someotherguy]

Cleaning and re-lubing the slider mechanisms on the vent position actuator has been covered quite a bit and is the most likely suspect area.

Richard

Was this ever looked at? All I see is in your post #2 that it "fixed itself" - things don't fix themselves.

Richard