# '85 300Zx A/C or Engine heating issue.



## Narche (Sep 2, 2004)

I hope you'll all excuse me if I don't come across in the most technical manner. My longstanding forté has been hands-on PC work, and I decided to broaden my horizons into vehicles, to which I have not quite mastered.

Here's the crux of my problem. I recently purchased an '85Zx and I'm having a problem with the engine "leaking" heat through the air vents into the car. I apologize for not having the exact information on hand, but the engine itself is not running abnormally hot. I replaced the thermostat a few weeks ago, thinking that may be the issue.

Now I know that the A/C unit is not charged, however the fans are operational and the control panel is responsive. The only problem is that when the engine warms up, it in turn warms up the passengers. I currently live in Southern California, so you can imagine the agony of cruising down the already crowded and congested freeways in 105 degree weather and having 120+degree air coming through your vents.

Does anyone have any suggestions as to what may be the root cause of this issue? I'd like to be able to do the work myself, however if it's a serious issue, I'm not at all opposed to having to take it in for professional service.

Thanks in advance.


----------



## Zen31ZR (Mar 24, 2004)

Make sure your temperature selector is turned all the way down. I keep mine at 60 degrees for all but the coldest days. You may also wish to see if the "recirc" function works , I think A/C mode has to be selected for that. That should cut off all outside airflow. Play around with it , don't be shy. If the digital temperature readout is still working , see what ambient temperature the car thinks it is. A malfunctioning temp sensor (It's up on the roof , inside the dome light housing) will cause some unusual problems of this nature. If it's 100 degrees out and the temp readout says its 50 , well there your problem. It may also be an in-dash malfunction , but those seem to be kinda rare. My 85 still works perfectly and the car itself is not in the best condition.


----------



## ccog425 (Sep 16, 2004)

I had the same issue with my '85 300 as well. I found the problem to be a faulty vacuum supply to my heater contol valve. The job of the heater control valve is to shut off coolant flow to the heater core.when the valve is open hot coolant continually flows through the heater core, allowing only hot air through the vents. the valve is vacuum controled, therefore if the vacuum supply is disconected or leaking,the valve cannot properly shut off coolant flow. 
check the vacuum line to the valve for leaks.(the heater control valve is located on the coolant line that supplies the heater core,near the firewall on the pass. side.)If the vacuum line is connected and no leaks are found,you might want to check the solenoid valve that controls vacuum to the heater control valve.

hope this helps... :thumbup:


----------



## '85 fairlady (May 1, 2004)

my best guess is it's a vacuum line when that shit gets old it becomes briddle and stiff and breaks get you self a hanes repair manual.


----------



## 0341TODD (Nov 15, 2003)

Mine does the same thing- its the vacuum lines- mine are shot by I say screw it- I live in florida and I just drive with my window open- I dont want to rip my dash open and it doesnt get cold here so Im just going to bypass the coolant lines running into the car so I dont have hot ass air coming in on me.


----------



## asleepz (Feb 24, 2004)

Mine is just the opposite. I never get any air that comes in when I don't want to. But my AC wouldn't go through. So I ripped my condensor and pump out and most of the lines. And I run with no t-tops and windows down when it's hot but I still get heat and defrosters so I am good when it does get cold.


----------

