The HVAC system on my 95 4X4 LS has been driving me crazy, and it’s getting to be a short drive. I bought the truck with about 160,000 miles on the clock, and from the start I wasn’t able control the HVAC system so that it would direct all the warm air onto the windshield in the defrost position, or all the air to the floor in the heat position. There was no difference in the vent output whether it was set to the defrost, blend, or floor heat control positions. No matter where the control was set, the amount of air coming from the vents was the same. This was cause for concern because during bad winter conditions, I couldn’t keep my entire windshield clear of snow & ice buildup. I had plenty of heated air, I just couldn’t put it all on the windshield, or all on the floor. So in search of a solution, I visited my friendly local bone yard, and robbed the vacuum actuators from a partially disassembled 97 Jimmy. Upon tearing into my blazer’s HVAC system, which requires the complete removal of the dash assembly, I vacuum tested the actuators and found the cause of the problem to be a leaking lower actuator. It connects to a door and controls the heat, blend, and defrost air. I replaced it with the good one from the bone yard. This cured my HVAC problems, and I was a happy camper again, but not for long. Unfortunately, the problem returned after about a year and a half, so I went to my Chevy dealer and was surprised to find the actuators were still available and ordered two new ones. They’re called upper and lower vacuum actuators, and I figured that since I was going to have to spend another 4 hours of my life tearing into the dash, I might as well replace both of them and put the problem in the past permanently with nice new GM parts! The total cost was $35 for the pair. Well, after installing them, the lower vacuum actuator failed after three months. I called the dealership with the news and they ordered another part for me for free. I installed it and everything worked as designed again until a couple weeks ago when the actuator failed again. I have yet to contact the dealership because my blood pressure is still a little high and I might say or do something I might regret. I’d like to get this thing working properly again, but don’t want it to become a yearly ritual. I’ve read other threads about broken doors etc and this is a different problem than what I’m having. Should I look at trading up to a Hyundai?? Anyone else experienced this problem or have a solution that doesn't involve explosives?

Thanks

 

Yours is a 4x4 model, correct? If so, have you noticed fluid in the vacuum lines? If so, this is generally not good for the vacuum system and can weaken the rubber diaphragms in the actuators. There was another thread I read recently where a guy kept having to replace his 4x4 actuator under the battery tray because the diaphragm kept ripping. He had noticed fluid, but didn't know why it was there.

 

Thanks for the link. It pretty much nails down the problem I keep having. I did some checking and found no ATF in the vacuum tank on the hood, but the vacuum lines at the transfer case switch were wet. I haven't pulled the fill plug on the transfer case, but the trans has lost fluid in the past so I expect to see it overfilled. I'm not happy about it, but I wouldn't have anything to talk about if nothing ever wore out!