Electronics Need help wiring something up? Thinking of adding an electrical component to your car? Need help troubleshooting that wiring glitch?

Heater controls

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Old Jan 27, 2004 | 01:36 PM
  #1  
90Iroc's Avatar
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Joined: Oct 1999
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From: Greenwood, IN USA
Car: 1990 Iroc/Z
Engine: LB9 305 TPI
Transmission: Borg Warner 5 speed
Heater controls

When I turn the heater on, all I get is front defrost no matter what setting I put it on. Even when I tried to put it on A/C. Last summer the A/C worked perfectly. What does this and how do I test parts to see what's bad?
Thanks guys

Brandon
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Old Jan 27, 2004 | 08:54 PM
  #2  
87PontiacBeast's Avatar
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Joined: Sep 2002
Posts: 390
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From: hazlet NJ
Car: 92 firebird
Engine: 305 tbi
Transmission: t-5
i have the same exact problem.
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Old Jan 27, 2004 | 11:20 PM
  #3  
3gc's Avatar
3gc
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Joined: Jul 1999
Posts: 917
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From: Long Island NY
Car: Z28
Engine: 350 TPI
Transmission: 700R4
Sounds like a vaccum problem not an electrical problem. I was just doing some research on this subject earlier today. I found both of my hvac vacumm lines melted. One of them connects to the intake for engine vaccmm, the other connects to the heater control valve. When the engine vacumm line isn't plugged in defrost is the default. So check to make sure that line is good. It's the purple line on the back on the heater controls.
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Old Jan 28, 2004 | 11:14 AM
  #4  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Often the switch, which controls where the vac is applied, leaks. Pull the control out; the switch in question is the one to which the vac harness attaches. If vac is present there, I assume you've found the culprit. Cured my problem anyway.

JamesC
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