HVAC Problem.

[ArthurC]

So today driving home in a winter storm I noticed the defrost stopped working and I had no ventilation coming out of any of my vents no matter what I selected. My immediate response to this normally would be the blend mode actuator wasn't moving - but I've replaced it and I manually tried adjusting the blend doors by hand. My blend doors have been jamming for quite some time now.

So this is the situation:

- Driving down the road I lost my defrost with no real notice. (it may have been blowing weaker than it should've been, but I didn't notice)
- I tried changing to all different vent types but couldn't get air out of any vents.
- I stopped at the next gas station and checked over the actuator which was in fact moving in a full range, and I manually tried moving the blend doors which they seemed to be free and moving (unless they are broken)
- I fiddled with it for a good 45 minutes with no results.
- Went into the restaurant and had a quick bite to eat (maybe 45 mins with truck not running)
- Returned to the truck, started it and immediately had ventilation again.
- 5-10 minutes down the road I lost ventilation again.

Anybody have any ideas? Is there any vacuum system that's attached to the HVAC on our 95-98 trucks? Did my blend doors break?

1998 k1500

 

[Eveready]

Since the problem is intermittent I would look at the electrical connection to the motor that runs the blend door. I have no personal experience but have read somewhere that this connection can come loose or become dirty and cause that sort of problem. Since it works part time the issue is more likely to be electrical than mechanical IMHO.

I expect others with more experience will comment further. Please let us know what it turns out to be.

 

[ArthurC]

Yeah I will for sure. When you mention the blend door do you mean the blend mode door? (The one by the gas pedal)?

I don't know if it's electrical as I tried manually moving the blend mode doors by hand and I still couldn't get any air moving anywhere.

EDIT: Got up this morning, checked the truck and it's blowing air again. When the truck warms up it slowly loses it's ventilation.

Yesterday's trip home was a disaster wiping the window every 3-4 minutes. Hoping we can figure this out.

 

[evilunclegrimace]

There is a blend door motor up against the firewall behind the fan mounting area. Check to make sure that it is opening fully.

 

[ArthurC]

Okay will do. Is that the one for the recirc? Or is it a completely seperate one? If I press recirc it opens the vent and changes the sound completely but still no air flow.

 

[east302]

The three actuators are electric, so there’s no vacuum control on them.

It seems like it would be something with the actuator by the gas pedal, as this one directs flow from floor to panel to defrost. If the linkage arms are intact and the notched dial rotates (roughly) from 10:00 to 2:00 position, then that should mean that the control panel is correctly signaling the actuator. I’d then wonder if you have something dislodged and stuck in there, blocking air flow intermittently.

I remember there being some foam seal in the air box but it could just as easily be a dislodged damper. See if there’s any means for removing the bottom of the housing and looking up in there. Otherwise, you’d be looking at rotating or pulling the dash to get in there.


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