spray around your vacum hoses with ether.
vacumm leak problem.
there is a vacumm leak .
Im haveing the same issue. Im assuming it is a vacumm leak causing it.
there could be more than one factor it sounds like the actuator is bad or if your blazer has partial vacumm control then you could have a vacumm leak
If it has the vacumm operated climate control check for a vacumm leak under the dash. Also check for proper operation of the vacumm valves operating the doors. Usually if the system breaks the control will default to the defrost position and vacumm leaks are a common cause.
Vacumm leak
You have a leak. You need to find and repair the leak.You have a leak. You need to find and repair the leak.
Most likely caused by a vacumn leak. check vacumn lines an vacumn hoses first. then check for loose intake manifold bolts. Bolts should be tightened to recommended torque. these are some of the simple fixes but a vacumm leak can be hard to find. you can try listening for a hissing sound but to me it is hard to hear while the engine is running. repair books recommend using a couple feet long rubber fuel line to hold one end to your ear while poking in the area(s) where the leak may be coming from. I would first just check the manifold bolts and the vacumm lines for cracks.
look for the leak once you find it you will know were the leak is have a great day =)
A vacumm.
Yes, there are some manufactures that sell an accessory pack that you can purchase seperate from the vacuum.
Disconnect the vacumm line at the throttle body. If fuel is spurting from the vacumm line then the reg is bad.