First post. I just bought a 1990 blazer. (very happy). I have a problem with not being able to shut heat off. Blower motor switch works. but in the off position its still pumping heat through vents that are selected. Anyone ever heard of this. The unit has air ( i was told that he never had it working) and it will just continue pumping heat no matter what the switch is on.

???

 

The problem is most likely a broken or disconnected vacuum line. The blend door actuator on the 1st gen vehicles is vacuum actuated. It could also be the actuator itself. It's been a while since I dealt with a 1st gen S10 or Blazer, so this is from (possibly faulty) memory.

Check the vacuum lines first. If you have a Mighty-Vac (or similar) vacuum test pump, you can test the actuator that way, too.

I was looking on YouTube, but all the "how to" videos I saw were for the later electronic actuator. Yours is actually more reliable.

Oh, and welcome to the forums here.

 

Thanks for help. You know what parts are compatible. Can't find an actuator on the net.

 

The actuator is GM Part # 1996700, AC-Delco part # 1571441.

It runs $30-$40. There are no aftermarket versions because that part rarely fails.

Check for vacuum first. Fix the broken/disconnected/missing vacuum lines and yours will probably work fine. If you buy a new one and don't fix the vacuum lines, the new one won't work any better than the one you have. You'll still have to find the issues with the vacuum lines.

It also might be the control in the dash. That is GM part # 16068295, and it's available mostly from $tealerships and online parts operations run by $tealerships.

There's always a disconnected or dry rotted hose. Fix that first.

 

Thanks again for taking time to help me out. Where are vacuum lines going to be connected. I'm assuming one end will be on actuator. Where's does it lead to and connect to. I'm very new to blazers.

 

It's been many years since I've dealt with one of these. I think there are two hoses from the actuator back to the control in the dash, and another one from the dash control, through a few "T" connections and a check valve, eventually back to the engine.

Is yours also stuck on defrost? Or does it switch between the floor vents, the dash vents and the defroster vents correctly?

 

Switches correctly