Heat/cold knob

LML

Hi from sweden!

Just got a 86 b2000 cab plus.
I noticed that the knob for the temperature was broken since it only pushed out hot air.

I fixed the control switch since the plastic was cracked and the cable had become unattached.
Now i see the cable move the linkage below with only a slight improvement to the air temp (still blows warm air on the cold setting)

How common is it that the damper plate gets stuck and how do i easily diagnose it without taking the whole assembly out.

Car doesnt have ac

Red91EFI

LML

My dash knob with the cable also quit working and I just move the hot water valve by hand . I'm too lazy to take the dash apart and replace the knob and cable.

MazdaMitch

Not very common that I know of I wonder if the metal cable is slipping somehow.

LML

MazdaMitch cable and gears are fine they move the linkage so the flap arm bottoms out as if i would do it with my hand.

Temp knob goes to last "mark" on either side but not all the way is that how it should be?

MazdaMitch

LML best I can remember when I pulled my dash and replaced the heater core and resealed everything with new foam that it does close all the way.

Maybe that's what's wrong is yours is missing foam it does disintegrate over the years.

LML

MazdaMitch yeah i figured that too, so it lets the warm air escape into the cab

MazdaMitch

Well now that I thoroughly read it better I may have a better understanding of what you're talking about and there is a hot water valve basically near the gas pedal that the cold and hot knob operates.

What this does is prevent or allow hot water into the heater core.
When set to cold no hot water flows through the heater core it just holds water and just not constantly flowing therefore it's not constantly hot.

If your valve is not working or broken stuck in one position to where it's only allowing the flow of hot water then of course it's going to be hot you need to check that valve it's near the gas pedal under the heater core.