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i dont have heat in my truck 1980 4x4 its like the vents dont work right i v checked heater core and water valve there fine just not blowing hot air in the right place need help please

I had this problem in a different truck. The core was plugged up.

Try disconnecting the heater core lines (from the other end, leaving the lines hooked to the core) and putting a garden hose on one to flush it out. Run the water both ways until the discharge is clear.

i tried blowing out the heater core and i got heat but its like the vent is stuck open and it wont switch over to heat

Do you have a manual? If not , just look around on the sides of the heater box for anything that looks wrong.
Look where the control cables come from the knobs, and follow them to where they go. Are they hooked up? If yes and you think it's a door problem, it could be a broken door internally. This happened to me on my '72 GMC 1 ton.
Move the knobs do you hear and thing moving? Are they hard to move or very easy? Just use common sense and start with the basics. Process of elimination.

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OK, I'm over it. Where's the beer?

thanks for the help i ll try that next

Also, is the blower fan running?

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OK, I'm over it. Where's the beer?

yes the blower motor is working fine thanks for the help

The '78 I have has an earlier vent box/heater control in it. I have no idea why, but it does. Anyway, there are a couple of levers on the pass side which control the direction of flow. When it's working properly, the slider controls move these levers to switch between the vent, defrost and floor heat. What I have to do is to push the slider to defrost and then reach over and make the lever on the heater box move. It's a pain, but once I've got it set I usually just leave it.

Anyway, it's easiest to just crawl in the pass side, and watch the levers while you move the sliders. Watch what happens, and see if the cables are moving but the levers aren't, etc. If the core isn't plugged and the blower is working, it's just a matter of pushing the heater box levers until you get the dampers open in the pattern you want (floor, defrost, etc.). It sounds like the end of the slider cable that should be hooked up to the levers has come disconnected. The other thing that can happen is the clip that holds the cable in place will come off, and then all that happens when you move the slider is that the cable bows without enough force to move the lever.

With the fan on, do you get cold air coming out of the vent below the sliders? If you do, then the levers need to be moved around until you close the outside air intake. Just getting that damper to close will help a lot with heat in the cab.

Hope I haven't over complicated this, it's pretty easy to figure out once you start looking at it.

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"If we did the things we are capable of, we would astound ourselves" - Thomas Edison

i v looked at all that but i'll look again maybe i miss something thanks for all the help