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post #1 of 8 (permalink) Old 01-25-2016, 05:52 PM Thread Starter
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No heat

Had this problem for some time. No heat. I can get a little warm air out of the vents on WOT in 4th or 5th gear on a long pull, otherwise it just blows cold. AC works properly. All vacuum lines underhood have been replaced (issue was around before and after that), and I'm reasonably sure everything is routed correctly. Car has the manual heater controls and not the digital heater. Where should I be looking for the issue? I'm sure it's vacuum related, but other than vacuum line routing could the issue be something else?

1985 300ZX
1998 Ridiculously built solid axle 4x4 Frontier
2012 Murano LE AWD
2007 Ram 2500 Cummins 4x4
2008 Boulevard C90T
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post #2 of 8 (permalink) Old 01-25-2016, 10:16 PM
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is the vac line into the cabin intact after i passes thru the firewall? Not sure about the manual system but the coolant control valve mounted on the fire wall requires vacuum to close. try pulling the vacuum line off of that and see if you get a lot of heat. get the fsm from xenon be a big help. crimped coolant hose could be a part of it.

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post #3 of 8 (permalink) Old 01-25-2016, 11:04 PM
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I have to ask whether any of the tests from the FSM have been performed, as per my suggestion in the previous thread by Desert Rat on this subject https://www.zcar.com/forum/11-84-89-t...-question.html

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post #4 of 8 (permalink) Old 01-26-2016, 04:35 AM
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http://www.xenonzcar.com/z31/HVACReconditioning.html

Read this. More than likely you will need to rebuild your heater box as all the controls are done via vacuum.


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post #5 of 8 (permalink) Old 01-26-2016, 02:36 PM Thread Starter
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Originally Posted by Mister_T View Post
I have to ask whether any of the tests from the FSM have been performed, as per my suggestion in the previous thread by Desert Rat on this subject https://www.zcar.com/forum/11-84-89-t...-question.html

If only this were in English:


The temp slider just changes the position of the air mix doors. The air mix doors control how much air passes through or bypasses the heater core.
So that the control unit knows the position of the air mix doors, there is a Potentio Balance Resistor attached to the linkage.
The 86 FSM I'm looking at has pretty good diagrams and trouble diagnoses for checking the abnormal condition of "outlet air will not become warm".
Hopefully it is just the solenoid valve pack that is faulty, specifically SV6 and SV7 which are combined into a Double Sided Solenoid Valve ("DSVV"). The DSVV turns vacuum on and off to the actuator that works the air mix door linkage.

The air mix door linkage could just as easily have been operated by a cable, but DSVVs, Potentio Balance Resistors and electrical sliders are more elegant.




Rather than getting the full technical diagnostic procedure from the FSM, I'm asking in an internet forum in case someone else had the same issue and found an easy fix, assuming it may be a common problem.


Where is the DSVV for instance? Does it require dash disassembly to get to or is it mounted someplace I can get to with a screwdriver? And from my other thread, the potential for heat is there. If unplug vacuum lines under the dash I'll get nothing but full heat coming out the defog vents. That rules out any crimped heater hoses, etc.

1985 300ZX
1998 Ridiculously built solid axle 4x4 Frontier
2012 Murano LE AWD
2007 Ram 2500 Cummins 4x4
2008 Boulevard C90T
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post #6 of 8 (permalink) Old 01-27-2016, 02:06 AM
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Quote:
Originally Posted by Desert Rat View Post
If only this were in English:


The temp slider just changes the position of the air mix doors. The air mix doors control how much air passes through or bypasses the heater core.
So that the control unit knows the position of the air mix doors, there is a Potentio Balance Resistor attached to the linkage.
The 86 FSM I'm looking at has pretty good diagrams and trouble diagnoses for checking the abnormal condition of "outlet air will not become warm".
Hopefully it is just the solenoid valve pack that is faulty, specifically SV6 and SV7 which are combined into a Double Sided Solenoid Valve ("DSVV"). The DSVV turns vacuum on and off to the actuator that works the air mix door linkage.

The air mix door linkage could just as easily have been operated by a cable, but DSVVs, Potentio Balance Resistors and electrical sliders are more elegant.




Rather than getting the full technical diagnostic procedure from the FSM, I'm asking in an internet forum in case someone else had the same issue and found an easy fix, assuming it may be a common problem.


Where is the DSVV for instance? Does it require dash disassembly to get to or is it mounted someplace I can get to with a screwdriver? And from my other thread, the potential for heat is there. If unplug vacuum lines under the dash I'll get nothing but full heat coming out the defog vents. That rules out any crimped heater hoses, etc.
I already gave you a link to my site that shows you the heater box as well as the actuator that works the air mix door linkage. Please review this link. Yes you will need to remove the dashboard to get to the heater box and actuators.


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post #7 of 8 (permalink) Old 01-27-2016, 01:34 PM Thread Starter
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missed that link. Will check it out. Thank you.

1985 300ZX
1998 Ridiculously built solid axle 4x4 Frontier
2012 Murano LE AWD
2007 Ram 2500 Cummins 4x4
2008 Boulevard C90T
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post #8 of 8 (permalink) Old 02-02-2016, 05:32 PM Thread Starter
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Kooky thing started working on its own today....LOL Wonder how long that'll last.

1985 300ZX
1998 Ridiculously built solid axle 4x4 Frontier
2012 Murano LE AWD
2007 Ram 2500 Cummins 4x4
2008 Boulevard C90T
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