I have a 1996 s10 4x4 blazer everything on heater works core is good blower is good switches when on the road for a while the heats stops blowing out you can hear it and it just barely comes out and its hot its just like the door is closed up on it is there a tip trick or a bad part how hard is it to get to any help is much apreciated!!!!!

1996 s10 4x4 blazer 4.3 v6 right at 200,000miles well taken care of daily driver

 

Vacuum leak behind the dash maybe? When there isn't enough vac to hold the door open it defaults to closed maybe? Then at idle it creates enough vac again to reopen it.

 

Thats what i was thinking. Is there more than one? and now a location? know where i can get that info? besides going and getting a hanes manual?

 

Save your money on the Haynes manual, unless you need help with an oil change
Inspect the vacuum check valve, vacuum lines and actuators. As mentioned, if there's a vacuum leak in the system, it will default to full heat and air flow will switch to defrost. There are 4 different actuators under the dash, 2 of them are dual function. The heat/defrost blend door is the first to change position with low vacuum. It's located just above the gas pedal, next to the transmission tunnel, and has a blue and a red vacuum line connected to it.

 

yeah the flow stops all together comes out nowhere just very lightly and can hear blower running

 

Set the mode switch to defrost and see if it acts up. If it doesn't, you have a vacuum leak.

 

Ok the defrost quits too does that mean its an actuator? or both maybe? I have noticed the switching process is very slow it takes a good 40 seconds to a minute to get to full defrost

 

Had same issue, I had 2 seperate leaks under the hood... One located at the check valve to the vacuum resevoir (in my fender, may be a stand alone on a 96)

The other was on the passenger side by the fire wall, it was a really flimsy tube that was maybe 4 in long and 's' shaped.

 

Ahhhh, new information
1996 4WD uses a vacuum switch on the transfer case for operating the clutch on the front axle. Both HVAC and 4WD share the same vacuum system. There is a seal inside the vacuum switch and if it leaks, it can suck transfer case fluid into and throughout the entire shared vacuum system. If it sucks too much fluid in, the HVAC actuators, and the axle actuator will operate slowly. Start by checking the fluid level in the transfer case, make sure it's level with the bottom of the fill plug hole, (uses DexronIII fluid). Next, remove the 3 vacuum lines from the vacuum switch. The switch is located on the driver side of the transfer case, inboard and slightly above the front driveshaft yoke at the case. If transfer case fluid runs out of the lines or switch when you remove the lines, the vacuum switch needs replacement. The entire HVAC & 4WD vacuum system must be cleaned out, including all affected actuators, lines, mode switch, reservoir etc.

If fluid does not run out of the vacuum lines, do a happy dance and inspect the vacuum lines, check valve and reservoir, starting at the engine.

If the lines appear OK, put a tee with a vacuum gauge at the vacuum reservoir and kink off the line going to the transfer case vacuum switch. Idle the engine to build up vacuum in the system. Shut the engine off and make sure the vacuum does not drop for about 10 minutes. Repeat this procedure for each position on the mode switch, this will check all actuators and lines under the dash. If there are no leaks, kink off the HVAC line and repeat the procedure for the 4WD vacuum system.

That ought to keep you busy for a while Post your results.

 

Mine did that to, I have a 97 4x4 s10 Blazer, the blower was bad, somthing with the coil in the blower motor.