Hi, I'm trying to trouble shoot something before I start taking things appart. When I step on the gas the AC/Heater which might be blowing out of any of the vents sounds like it goes somewhere in the dashboard and stops blowing as hard out the vents that I have selected for AC/heat to come out of. When I let up off the gas the vents blow hard AC blows cold but Heat now blows cold. I can hear the actuators working perfectly as long as I don't apply the gas, as soon as I apply the actuators move the air some other place. Any ideas? Thanks Max
Krash, yes they are vacuum operated because I can hear and feel that they are vacuum operated. Do you know, off hand, if this requires that I pull the whole dash out or is it easier than that? Just getting an idea, because I can pull the controls out and replace the vacuum hoses. Thanks for looking at this. Max.
I remember our 71 Olds blowing out wrong vents for HVAC setting and finding one hose unplugged under the dash, fixed it right up. Bet there's lots of hoses under that hood, start tracing them. Good luck.
when u take a look under the hood , there oughta be a in line check valve in the vacuum line leading inside .u should be able to pull vacuum from one end but not the other . if you dont see or hear a vac leak this could be your problem . good luck with'er!
You have the most vacuum when you let off the gas and it may be overcoming a leak , bad line, actuator , valve or switch only then. The hot water valve probably isn't opening and letting heat in without proper vacuum too, why the temp is cold when it should be hot. That's unless its the type that holds it closed, then it would be hot all the time without vacuum. The car idle okay?, notice any changes in it? Do you have a factory service manual? Usually they have detailed troubleshooting charts for those type problems and tell you exactly what to look for and how to go about it. If you have a mityvac tool you can check all that stuff for leaks and function, a lot easier than trying to do it with the engine running or by looking at them.
Not sure about your car but on mine there is a vacuum accumulator tank buried in the fender. It looks like a black plastic blimp. That would be another place to check. My HVAC vacuum lines would always crack on the underhood side, right near where they go through the firewall. I've had 3 cars do that.
what did you find out? I've got an 89 and a 90 colony park and fixed both of them up. There is no heater control valve on these cars, so that's not your problem if you have manual temperature control, that particular blend door is also not vacuum controlled. However, for mode (windshield, dash, floor selection) that's vacuum. Like already stated, when you give it gas, vacuum drops a lot. I put a vacuum gauge on my car just for the hell of it-- I get 20" at idle in gear at a stoplight, but as soon as I hit the gas it drops to 5". Cruising at idle on the highway, maybe 10". WOT of course is 0". There is a vacuum reservoir that is supposed to store vacuum just for this reason, and there's a one-way check valve so that it keeps that vacuum. Vacuum reservoir is happily not hidden in the fender, but on an '87, is literally a steel can on top of the driver's side fender. Looks like a tin can from the grocery store! Actually, a leak there is very common! 1990 replaced this with a plastic box. If you can't smoke test, another test is to start the car, and then spray brake cleaner around the vacuum reservoir can. If you hear the engine idle change abruptly, that means it just sucked in brake cleaner and burned it... and if it sucked in brake cleaner, there was a vacuum leak where you just sprayed! I'd smoke test it and look for leaks. And I'd verify that that check valve is working. If it's stuck open, your vacuum operated climate controls are operating on exactly the vacuum level in the intake, be it 20" at a stop light or 0" accelerating on the highway!! It's probably an easy fix just to replace it anyhow; although, you DO need to remove the upper intake to get to it. 2 hours if you don't know what you're doing/ haven't done it before. Excellent time to do valve cover gaskets or egr coolant lines or the pcv valve/grommet/screen while you've got the upper intake off!
