Low air flow through dash vents.

[Kelly Mac]

I have a 86 C10, with factory AC. I have been working on getting the AC and Heat to work correctly, this forum has been lots of help. So thanks. My dash vents dont blow enough air. This includes the two on the passenger side and the one in the gauge bezel. My AC blows cold with real good flow from the floor vents and from the defrost vents. I have good heat from the defrost and the floor vent when needed. I have checked my vacuum actuators and they move as they should.
I was going to seal up any gaps with HVAC tape and foam and do the blower motor upgrade. Anyone have any other ideas on what could be going on?

 

[1987 GMC Jimmy]

Your high fan speed works so we can eliminate a bad relay? Go ahead and check the vacuum line coming off the back of the intake. It should split two ways at a check valve and one side should go to a tube by the evaporator case. If the line is disconnected or if the check valve is damaged, especially, or if the check valve is not there, your issue will most definitely come up. If this doesn’t fix you, I’d go behind the dash and check the ducting to make sure it’s connected properly. I’m willing to bet it’s the first thing, though. I’m assuming the duct on the last vent is disconnected since you didn’t mention it.

 

[yevgenievich]

there is a diverter door accessed from inside the cab by taking the vent cover off the hvac box. Very often the plastic piece that actuates it brakes.

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[Kelly Mac]

Thanks, my plastic is new but the plastic door connected to it via a metal rod, seems to be broken. It was blocking the metal door from opening up and letting the AC air through the dash vents. I'm looking around for another heater/ac box to see if my door really is broken. Also, on max AC my recirculation vent opens, but it closes on Norm AC, is this correct?

 

[1987 GMC Jimmy]

Thanks, my plastic is new but the plastic door connected to it via a metal rod, seems to be broken. It was blocking the metal door from opening up and letting the AC air through the dash vents. I'm looking around for another heater/ac box to see if my door really is broken. Also, on max AC my recirculation vent opens, but it closes on Norm AC, is this correct?

Yes, MAX is the recirculating air setting, and NORM is the ambient air setting.

 

[Johnnye23]

Anyone have a part number for the diverter door plastic arm ? Thanks