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GM style climate control question
I'm investigating Suburbans, the 92 to 99 body style. I test drove on the other day that seemed in good shape but was puzzled by sounds coming from the firewall area under the passenger side of the dash, down by the black contraption that I assume is the blower motor/evaporator box. Although the AC worked fine every now and then varying between several times a minute and every couple of minutes there was some kind of noise like a flap that would open or close with a substantial hissing and banging sound. Sorry, no other way to describe it. Not very loud just enough to be noticable over the sound of the vehicle at speed. I'm guessing that might have something to do with vacum actuation of the air flow in these things. Does anyone have any idea if that might be right or if it could be something else? I assume this is essentially the same system used in all full size GM pickups of that era? If so would replacement of this unit be a problem?
- Peter.
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2021 Chevrolet Spark Formerly... 2000 GMC Sonoma 1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021 2002 Kia Rio. Worst crap on four wheels 1981 240D 4spd stick. 389000 miles. 1984 123 200 1979 116 280S 1972 Cadillac Sedan DeVille 1971 108 280S |
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I don't think it's normal because our 97 'burb makes no such noise. Certainly not to the degree that it sounds abnormal. There's a rather long hiss when you turn off the engine with the AC compressor engaged. It can go on for half a minute. I'm told that's normal.
I have to wonder if it's a vacuum system, though. Our 6.5TD engine vacuum pump serves only the wastegate actuator. Brakes have hydraulic assist. Maybe there's an electric vacuum pump for climate control. Sixto 87 300D |
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yes 88 up chevy pickups us an all electric hvac system.
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So if that's the case then it's likely and electrical issue.?
- Peter.
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2021 Chevrolet Spark Formerly... 2000 GMC Sonoma 1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021 2002 Kia Rio. Worst crap on four wheels 1981 240D 4spd stick. 389000 miles. 1984 123 200 1979 116 280S 1972 Cadillac Sedan DeVille 1971 108 280S |
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Or the flap isn't moving freely.
Sixto 87 300D |
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This sounds like a well known problem with GM and Ford HAVC systems. Where they used to use vac servos to move the blend doors they now use stepper motors. They are easy to install (once you get to them, that is) and take up a lot less room than a servo.
Normally they will make a clicking or thunking sound and on GM's will do it even if the key is off. There is no repair; the one that is bad just has to be replaced. I think they run about $70 each for parts. The good news is that it will not get any worse. The bad news is that some of them are very difficult to get to. |
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IIRC........ the recirc door is probably the one misbehaving. R/R the glovebox, actuator is on top of the case behind it...........done!
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Actuator. That was the word i was trying to think of earlier.
You might be able to go to Rock Auto's web site and get a picture of the one you need. The ones I have seen look like big electrical breakers without a switch. |
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Very interesting and useful info as usual folks, thanks. I have not bought the vehicle, I'm merely starting to look around at them as there are a plethora of them going dirt cheap in this part of the wolrd. I've never owned one nor driven one so I figured I'd start testing as many as I could to find out what's what. Might be able to pick one up for a few thousand.
- Peter.
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2021 Chevrolet Spark Formerly... 2000 GMC Sonoma 1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021 2002 Kia Rio. Worst crap on four wheels 1981 240D 4spd stick. 389000 miles. 1984 123 200 1979 116 280S 1972 Cadillac Sedan DeVille 1971 108 280S |
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My reason for wanting one is really only as a secondary vehicle, intended for weekend and family vacation use. So I'm thinking a 2 wheel drive might be preferable as well, both for simplicity and better mpg's. I really can't see any use for a four wheel drive one. - Peter.
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2021 Chevrolet Spark Formerly... 2000 GMC Sonoma 1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021 2002 Kia Rio. Worst crap on four wheels 1981 240D 4spd stick. 389000 miles. 1984 123 200 1979 116 280S 1972 Cadillac Sedan DeVille 1971 108 280S |
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I have two of this body style beyond 1995. A 96 and a 99. THe 96 has 210k on it still clicking along. THe 99 has 150k. The only problems out of either were intake gaskets every 100k. The 96 was at 86k and 192k. I have replace a fuel pump once on the 96. THe brake about every other year. Brake parts for front run about $150 total. pads and rotors, I can change them in a about an hour. Other than that I have no complaints out of either of them. These are big heavy vehicle that also drink gas at a fair clip but not bad considering the size and wight. I run about 12-13 mpg in town and 17-20mpg on the highway. Both 350ci 4X4 models with a 3.42 rear. If you get a 2wd add about 2-4mpg to those figures.
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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K |
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My 05's has been flawless. I have 2 zones, the heat will cook you out on the coldest days and the AC will freeze you to death on 100 degree days. The 2 zones are a must IMHO since most women like it somewhat warm so they can adjust their side and not kill you with heat.
GM seems to do this very well.
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1999 SL500 1969 280SE 2023 Ram 1500 2007 Tiara 3200 |
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As for the split climate, that's not really an issue here. It's always on max cold all the time. This is Phoenix after all. You either need maximum cold or nothing at all. - Peter.
__________________
2021 Chevrolet Spark Formerly... 2000 GMC Sonoma 1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021 2002 Kia Rio. Worst crap on four wheels 1981 240D 4spd stick. 389000 miles. 1984 123 200 1979 116 280S 1972 Cadillac Sedan DeVille 1971 108 280S |
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