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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 08-13-2007, 11:38 PM   #1
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My brother-in-law just bought a 92 Bonneville and he can only get air through the defrosters. He says he has vacuum at the ports under the dash. I suspect a control door is stuck - any suggestions?
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Old 08-13-2007, 11:44 PM   #2
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Billboost will testify to my favorite suggestion:

Look for a vacuum line going into the firewall to the left of the brake master cylinder. There should be a black box there with a vacuum line running from it to the TB area. That one supplied vacuum to the HVAC system.
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Old 08-14-2007, 03:38 AM   #3
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had the same problem and the vacume line was off right at the black box in the engine bay.
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Old 08-14-2007, 08:26 AM   #4
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Great - thanks - I will have him check out your suggestions...
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Old 08-14-2007, 09:36 AM   #5
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If you have vacuum confirmed inside then there is a good chance there is a bad vacuum actuator. Although it is fairly uncommon.
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Old 08-14-2007, 11:20 AM   #6
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Missed that part. Could this be the valve behind the glove box?
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Old 08-14-2007, 11:59 AM   #7
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There are 3-5 valves which I've never gotten into. Unfortunately I don't think most of them can be accessed w/o pulling the dash. Although..the dash is an easy thing to pull.
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