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Old 03-17-2014, 04:09 PM   #1
oltronj
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heater problems

Does anyone have some pointers for troubleshooting the vacuum operated heater doors on a 91 GMC Suburban? Just bought it and the heater just always blows a little out of the dash almost like something is stuck but it won't change to the floor or the defrost. I know it is all vacuum operated. Just looking for some tips and tricks if anyone has any.
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Old 03-18-2014, 04:32 PM   #2
68Timber
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Re: heater problems

Lots of good info here.
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Old 03-19-2014, 10:51 AM   #3
Ski-me
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Re: heater problems

Look at the blending door and the infamous "broken tab".....
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Old 03-20-2014, 09:51 AM   #4
oltronj
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Re: heater problems

Got onto it last night and found a few rotten vacuum hoses and it's working now. All I have left is to figure out why the blower won't go to high. Thinking a bad relay or something, if anyone has ideas on that I would appreciate some guidance.
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Old 03-20-2014, 11:09 AM   #5
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Re: heater problems

Quote:
Originally Posted by oltronj View Post
Got onto it last night and found a few rotten vacuum hoses and it's working now. All I have left is to figure out why the blower won't go to high. Thinking a bad relay or something, if anyone has ideas on that I would appreciate some guidance.
There is a silver, rectangle relay mounted on the heater box (or next to it) inside the engine bay. A lot of times this goes bad making the high fan not work. You could try a junkyard one or get a new one at Autozone or Napa.

http://www.autozone.com/autozone/par...er=946055_0_0_
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Old 03-20-2014, 07:22 PM   #6
oltronj
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Re: heater problems

I found one at a junkyard and will give it a try thanks.
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