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Looking for some help with a heating problem. The heat appears to be on all the time regardless of where the cold/hot lever is. It mainly blows out of the defrost and seems to increase with acceleration. 1986 non-turbo 300zx with a/c but depressing that button doesn't seem to change anything. The fan switch and motor work to get it even hotter so I leave that off. Any ideas?

Thanks.

Rick
 

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yes, vacuum leak. you could have a leak under the dash (ouch) or in the engine compartment. check the engine compartment for split or disconnected vacuum tubes (you might also hear hissing). I have a website that shows where teh vacuum tubes under the hood go but Im at work and cant get to my computer. sorry.
 

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Very high possibility as sportdriverGT says. I had and a lot of us have had vacuum leaks that cause this problem. First look under the hood on the passenger side hoses. It seem they get really brittle there and crack causing the leak. I would say that the engine compartment is more suspect than inside do the extra heat imposed on the vacuum tubes there.

Inside near the driver footwell is a vacuum distribution center. Maybe you kicked a hose loose .... or busted off a connector there with your foot. That is less likely. After that all you can do is listen or start replacing the tubes "one at a time" Let me express "one at a time" If you get them mixed up it's heck to straighten them out.

Good luck.
 

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Find the heater valve at the back pass side of the engine and wire the lever up to stop the heat...then fix the vac leaks and so forth?
 

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I am having the same problem, from what I have found out there is a default positon that blocks the air and forces heat through the defrost vents., What I am trying to find out is what makes the door stay open?
I have already changed all the vac hoses and tested the vac system.

z4life
 
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