Quirky HVAC System - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 11-03-2006, 01:40 AM   #1
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Default Quirky HVAC System

My HVAC system seems to be working rather odd, ever since i bought the car. The vents seem to stay stuck in the defog position for a long while until the car has sufficiently warmed up (say 20 minutes), even if the auto-control is set on floor or body vents only. I read somewhere that this is a feature that adjusts the vents and blower according to engine temperature, (so as not to blow cold air in your face on a cold day) but it seems a little extraordinary to me.

Is the system operating properly? Also, the blower seems to be a little weak. Is that just a common thing with these cars since there is more ductwork to push air through? The blower on my old Escort pushed air out much faster compared to my Bonnie.
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Old 11-03-2006, 10:43 AM   #2
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Is your inside getting good vacuum from under the hood? Check hose at right side of car next to the air conditioner dryer unit (quart size silver tank). There'* a small 1/8 inch diameter slick black hose that has a T. One lead goes to the storage under the right front fender in front of right wheel. One lead goes back to intake manifold. One lead goes to the inside of the car.

Does motor have lots of mileage and wear causing lower vacuum?

There is a connector inside the car that can deteriorate and has little nipples of thin plastic that covers over the vacuum opening inside and blocks vacuum from door motors. This can be bypassed. The dash vents work requiring one motor to block off flow from heater at bottom and another door to close the door that keeps air from going out defroster.

If you need to find if you have good vacuum, take off hush panels under the dash. Run motor and switch from one setting to another every 10-15 seconds. If you can't hear the motors swish as vacuum goes into and out of the motors, turn off car motor and push a button to change from setting to setting. You should have enough vacuum for 3 or 4 changes before the storage tank is depleted.

The connector that has plastic that softens and blocks vacuum (air) flow is behind and under the glovebox. It has 7 connectors IIRC, each with a 1/8 inchplastic line of different colors.
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Old 11-03-2006, 12:03 PM   #3
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Quote:
Originally Posted by imidazol
The connector that has plastic that softens and blocks vacuum (air) flow is behind and under the glovebox. It has 7 connectors IIRC, each with a 1/8 inchplastic line of different colors.
I agree with imidazol, sounds like a vacuum issue at this point. The vacuum connector he'* talking about under the glovebox area actually has 6 connections with 5 vacuum lines going into it - one of the connections is empty. There is a procedure for fixing collapsed nipples on this bb, do a search for it. BTW, if you had a '93 you wouldn't get collapsed nipples because the plastic is more rigid - lol!

Also your low airflow could very likely be caused by a clogged heater core. There are also procedures for cleaning this here, search for it or wait for one of the superposters to give you the link!
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Old 11-03-2006, 12:47 PM   #4
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Quote:
Originally Posted by SSE Motorhead


I agree with imidazol, sounds like a vacuum issue at this point. The vacuum connector he'* talking about under the glovebox area actually has 6 connections with 5 vacuum lines going into it - one of the connections is empty. There is a procedure for fixing collapsed nipples on this bb, do a search for it. BTW, if you had a '93 you wouldn't get collapsed nipples because the plastic is more rigid - lol!

Also your low airflow could very likely be caused by a clogged heater core. There are also procedures for cleaning this here, search for it or wait for one of the superposters to give you the link!
I assume the SSEi has the dual auto air.

He didn't say how many miles. I could be low engine vacuum because of problems in the motor. It could be a cracked storage tank for the vacuum. It could be several things.

You're right, it could be a plugged heater core (can that be checked by taking out the blower motor?) And the blower motor might not be running right after lots of hours of use. Knocking on the blower motor while it'* running might loosen the rotor and make it speed up if a bearing is rubbing. does the blower motor slow down gradually when power is turned off? Quick stop might mean lots of friction.

It could be a vane in the heater duct not moving like it should and partly blocking air flow. I'd have to hear the sound of the blower to really make a guess.
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Old 11-10-2006, 04:11 PM   #5
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I had this exact problem for some time and finally it stopped changing airflow altogether and is stuck on defrost. I plan to work on that this weekend since all of my other car problems seem to be fixed for now. If I find the problem I will post it here.
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Old 11-10-2006, 06:05 PM   #6
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Ok.. we need the nipple post and whatnot.. Off to get info for you guys.
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Old 11-10-2006, 06:09 PM   #7
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Ok.. here'* a link. You must read the ENTIRE thing.. there will be a quiz later and if you read it all, find the nipple link and read that..

Then you will spend almost no time diagnosing or fixing the issue. If you don't read it all.. you'll be at this for days

http://www.bonnevilleclub.com/forum/...highlight=hvac

I know..it'* 7 pages.. It'* worthy.
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Old 11-11-2006, 12:48 PM   #8
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Wow, good read.

Are the pictures from that thread available anywhere? I got a lot of red x'* that probably used to be invaluable information.
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Old 11-11-2006, 12:51 PM   #9
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Uh.. hang in ...lemme check with Echo.
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Old 11-11-2006, 02:51 PM   #10
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Okay so I've checked vacuum for the purple line by accessing the T under the Maxifuse panel and blowing into it. There was no leak. So I moved on to the programmer per the write up. I have removed the female connector and am looking at six nipples. They are all very soft and flexible, although none broke when I removed the female connector. The repair article referenced in that thread says to remove the programmer. Is this necessayr or does just the soft nipples have to be replaces with healthy 1/8" vacuum line? That appears possible without removing the programmer. If the programmer must be removed, how is this done? I see no way to remove it. No bolts or anything. There is no access of any kind from the glove box.

Any idears?
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