Heat on all the time - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 9 (permalink) Old 06-26-2017, 09:34 AM Thread Starter
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Heat on all the time

Hi, I have an 86 turbo, with digital controls. The air conditioning does not work, and I have full heat coming from the vents all the time no matter where I set the temp controls. If anyone has any ideas I would appreciate your help.
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post #2 of 9 (permalink) Old 06-26-2017, 11:51 AM
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Does your car have a digital or analog dash?

1984 300zx non-turbo
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post #3 of 9 (permalink) Old 06-26-2017, 01:31 PM Thread Starter
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Hi, It has the digital dash and climate control
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post #4 of 9 (permalink) Old 06-27-2017, 09:46 AM
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you most likely have a vacuum leak.. under the hood on the passengers side behind the headlight it the vacuum tank. there is a vacuum hose with 2 wires near it. this controls the heat valve. the heat valve is located on the passengers side by the battery you can try and run a new hose to it. but i would recommend replacing all the vacuum hoses.

http://www.thumper300zx.com/z31/vacuum/vacuum.htm
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post #5 of 9 (permalink) Old 06-27-2017, 01:42 PM
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replacing vac hoses may solve your issue (and you should do it anyway) but if the digi control box not working right as is mine you need to get vacuum to the coolant control valve. I used the wiring going to the headlight washer pump which I never used for anything except " hey look what it does" to gawkers. mounted a rocker switch in the center console that turns the vac switch solenoid valve on the vac tank mounted up on rail right side of eng room. when I need heat I flip the switch to energize the vac solenoid and voila heated fluid enters the system. No heat when I flip it off. or just run a vacuum line to the coolant valve. look at the valve when the engine is running if it is in the down position it is wide open. only has two modes open or closed. needs vac to close. failure mode is wide open and lots of heat in the cabin.

86T, 350 Nismo 08 (#1415) gone but fondly remembered 81T, 83T, 83, 85T, 86T, 96TT

Last edited by rogerz; 06-27-2017 at 01:45 PM.
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post #6 of 9 (permalink) Old 06-29-2017, 07:20 AM Thread Starter
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Thanks for your help! I will update my post once i get it fixed.
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post #7 of 9 (permalink) Old 06-29-2017, 07:21 AM Thread Starter
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Quote:
Originally Posted by rogerz View Post
replacing vac hoses may solve your issue (and you should do it anyway) but if the digi control box not working right as is mine you need to get vacuum to the coolant control valve. I used the wiring going to the headlight washer pump which I never used for anything except " hey look what it does" to gawkers. mounted a rocker switch in the center console that turns the vac switch solenoid valve on the vac tank mounted up on rail right side of eng room. when I need heat I flip the switch to energize the vac solenoid and voila heated fluid enters the system. No heat when I flip it off. or just run a vacuum line to the coolant valve. look at the valve when the engine is running if it is in the down position it is wide open. only has two modes open or closed. needs vac to close. failure mode is wide open and lots of heat in the cabin.
Thanks for your fix! That's a great idea....
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post #8 of 9 (permalink) Old 06-29-2017, 07:59 AM
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http://www.xenonzcar.com/z31/hotairfromac.html


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post #9 of 9 (permalink) Old 09-08-2017, 08:10 AM Thread Starter
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Fixed

Thanks to everyone who answered my question. It was the vacuum line going to the watercock that was cracked and leaking. I cut the line back to a spot where it was not cracked and brittle and connected it back on....problem solved.
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