Community Forums

dynoguy · 12-28-2022, 09:00 AM

Wonder if someone could direct me to a schematic for the HVAC system. I believe I have a blend door issue and want to see where its at before I tear the dash apart.

sandy1 · 12-28-2022, 10:54 AM

I would start with checking vacuum lines. The system defaults to defrost vents only if there is a vacuum leak. Vacuum pump and accumulater are located on firewall above generator on drivers side. You can disconnect line from acculimator and cover to see if vacuum builds up and pump stops. Then follow line inside firewall. Remove panels in from of passenger seat. Following line it will go to a small vacuum/electric solenoid (common failure part) line from this goes to back of dash air selector. From selector colored vacuum lines go the actuators on dash doors. As you come to each connection disconnect and see if vacuum builds up and pump shuts off. If it doesn’t the leak is between where you last tested to current location. You can check each actuator. Most parts are available from acmeair. Dash control is Chevy with heated mirror switch. You can pm me with any questions

andy29847 · 12-28-2022, 11:16 AM

andy29847 · 12-28-2022, 01:47 PM

I agree with Sandy that the most likely candidate is the vacuum system. The vacuum pump is on the firewall, behind the generator slide, located near where the throttle is on the other side. It is aggravating to remove. It attaches via bolts through the wall, and you have to remove the steering column cover and peel down the carpet to get at the fasteners on the inside. Normally, the pump will run some to pressurize the tank when you first start the system. The sound from the pump is audible from inside the cab. Below is a photo of the vacuum pump and another from inside the cab where the vacuum pump mounting bolts go through the wall.

dynoguy · 12-28-2022, 02:31 PM

Quote:

Originally Posted by andy29847

I agree with Sandy that the most likely candidate is the vacuum system. The vacuum pump is on the firewall, behind the generator slide, located near where the throttle is on the other side. It is aggravating to remove. It attaches via bolts through the wall, and you have to remove the steering column cover and peel down the carpet to get at the fasteners on the inside. Normally, the pump will run some to pressurize the tank when you first start the system. The sound from the pump is audible from inside the cab. Below is a photo of the vacuum pump and another from inside the cab where the vacuum pump mounting bolts go through the wall.

This is definitely running on mine. this is where I'll look first. Thanks.