Heater blend door.

[mavtricks71]

1986 k10 w A/C ............When my truck is running and on the heat setting ….is the front vacuum door supposed to close? im confused as my trucks apart....is it designed for hot air to come through the a/c registers in dash or only at your feet and defrost area at top?

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JUST LIKE THIS...IS THIS CORRECT???

 

[mavtricks71]

I wanted to say when I run through all the cycles all the vent doors open and close in all the right cycles. OTHER THAN when I put it on heat the front door closes diverting heat to floor.
WHATS RIGHT WHAT WRONG? HES HAVING EXACT OPPOSITE PROBLEM LOL

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[75gmck25]

GM made minor changes to the HVAC over the years, so the controls and door operation vary a little from year to year. For each year of truck, there is an HVAC control table in the shop manual, so you can download and read that page to see how it is supposed to work. However, I will warn you that the GM engineer who made this table seemed to also want them to be a test of reading comprehension. I've read through mine many times over the years and still have to go back and figure it out again each time.

For example, the table shows some vacuum port numbers that are completely plugged, or connected with a jumper passage in the factory vacuum connector on the controls. So what is the point of telling me about plugged/connected ports if its built in to the connector and there is no way to change it?

Bruce

 

[HotRodPC]

Do keep in mind, you have 2 blend doors too. 1 for Hot and Cold, and 1 for directing the air to floor, Bi Level or Defrost. You have vac diaphrams that control the doors. On my 86, one of those doors has both a push diaphram and a pull diaphram. Whichever one isn't working correctly. So I can turn on the defroster and it works fine. But then when I go to turn it off defrost and go back to the floor or Bi Level, it won't go back until I shut the truck off and lose vacuum. Then start it back up and it's back to the floor or Bi Level. But, as said, there was a little change on the operation of the air handler along the way. But do keep in mind, some of the diaphrams are pushers, some are pullers. And do make sure you're working with the correct blend door.

 

[HotRodPC]

I wanted to say when I run through all the cycles all the vent doors open and close in all the right cycles. OTHER THAN when I put it on heat the front door closes diverting heat to floor.
WHATS RIGHT WHAT WRONG? HES HAVING EXACT OPPOSITE PROBLEM LOL

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As I said above, there's pushers and pullers. I wonder if he doesn't have 2 vacuum lines reversed. He could have one line going to a pusher when it should go to the puller, and on the puller when it should go to the pusher. I'm fairly certain, 85 is same as my 86.

 

[mavtricks71]

As I said above, there's pushers and pullers. I wonder if he doesn't have 2 vacuum lines reversed. He could have one line going to a pusher when it should go to the puller, and on the puller when it should go to the pusher. I'm fairly certain, 85 is same as my 86.

Let m ask this when the switch is in the "Economy Vent" mode will heat come out of the a/c vents? Again this is my first k10 and it's apart.