Hey everyone, been lurking on this forum and using it as a resource as I work on my first gbody that I recently bought, decided to join to request some help. I'm not new to working on vehicles, but I haven't owned a carbed vehicle before, nor have I owned anything older than 1989. My Cutlass is a 1982 so it's about a generation older than anything I've really dived into. I have two of the typical HVAC issues going on. They are, (1) only hot air comes into the cab, no matter whether the temp setting is at 65 or 85. And (2) air only blows out the windshield and floor vents, not the dash vents. Splitting these up into the two respective issues:
1. Only Hot Air in Cab
As far as I understand, changing the temp inside the cab is done via two systems. One is the cable system that is right behind the glove box. I've heard this can break pretty easily and often needs repair. Took my glovebox out and tested this cable unit, it seems like it's working. I don't see anything broken. As this is my first gbody, I may be missing something. This is detailed in the video linked below. The other system that I believe controls the heat in the cab is the vacuum-actuated valve on the heater hose that goes from the engine to the heater core. This is a grey vacuum line. I assume the function of this is that when that valve receives vacuum, the valve closes? Or is it the opposite? I also showed this in the video, but there is no vacuum here when the hvac control is set to the lowest temp setting. I believe I forgot to test whether there is vacuum when the hvac controls are set to the highest temp. What am I missing here? If you have suggestions on how to diagnose, let me know.
2. Blend Door Not Working, No Air out Vents
As far as I understand, the "default" hvac blend door setting is to divert air to the windshield and the floor. So if your blend door isn't working, that's the default state it'll basically revert to. And if you want air to come out the dash vents, this is a vacuum-operated thing. My research has led me to believe this is that purple/pink vacuum line that goes through the passenger side of the firewall and connects to the vacuum ball that is to the passenger side of the engine in the engine bay. There is a vacuum line connector behind the glove box as well, as shown in the video. I removed the purple line from it, and the engine side of that line does have vacuum. It's not a lot, but there's some. Not sure what else could be the problem with the blend door not working. I have not yet removed the center dash vents to lubricate the blend door in the dash. I may have to figure out how to do that. Any suggestions would be great.
Video I recorded of the issues, might be helpful if I've worded things poorly above:
Thanks in advance for the help!
EDIT: For future readers, it seems I have what's called a Tempmatic heater/AC system. Some of this stuff may not apply if you have the regular heater system. If your original temp control has red/blue and hot/cold indicators, you have the regular hvac system. If you have the number 65 to 85 on your temp control, that's the Tempmatic system.
1. Only Hot Air in Cab
As far as I understand, changing the temp inside the cab is done via two systems. One is the cable system that is right behind the glove box. I've heard this can break pretty easily and often needs repair. Took my glovebox out and tested this cable unit, it seems like it's working. I don't see anything broken. As this is my first gbody, I may be missing something. This is detailed in the video linked below. The other system that I believe controls the heat in the cab is the vacuum-actuated valve on the heater hose that goes from the engine to the heater core. This is a grey vacuum line. I assume the function of this is that when that valve receives vacuum, the valve closes? Or is it the opposite? I also showed this in the video, but there is no vacuum here when the hvac control is set to the lowest temp setting. I believe I forgot to test whether there is vacuum when the hvac controls are set to the highest temp. What am I missing here? If you have suggestions on how to diagnose, let me know.
2. Blend Door Not Working, No Air out Vents
As far as I understand, the "default" hvac blend door setting is to divert air to the windshield and the floor. So if your blend door isn't working, that's the default state it'll basically revert to. And if you want air to come out the dash vents, this is a vacuum-operated thing. My research has led me to believe this is that purple/pink vacuum line that goes through the passenger side of the firewall and connects to the vacuum ball that is to the passenger side of the engine in the engine bay. There is a vacuum line connector behind the glove box as well, as shown in the video. I removed the purple line from it, and the engine side of that line does have vacuum. It's not a lot, but there's some. Not sure what else could be the problem with the blend door not working. I have not yet removed the center dash vents to lubricate the blend door in the dash. I may have to figure out how to do that. Any suggestions would be great.
Video I recorded of the issues, might be helpful if I've worded things poorly above:
Thanks in advance for the help!
EDIT: For future readers, it seems I have what's called a Tempmatic heater/AC system. Some of this stuff may not apply if you have the regular heater system. If your original temp control has red/blue and hot/cold indicators, you have the regular hvac system. If you have the number 65 to 85 on your temp control, that's the Tempmatic system.
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