XenonZcar.com - Z31 Getting Hot Air From AC even when set to cold temps

On the Z31 300zx there was two different designs of the Air Conditioning system used, A manual system used on the GL models that used sliders for adjustment and an automatic climate that was offered on GLL models as well as the 50th AE. This system was Digital and used sensors to monitor and adjust temperature and air flow.

We will be discussing the problems and fixes for both systems on this page.

Hot Air From A/C Vents

Commonly this is a vacuum problem without any one particular cause or fix.

  • Any leak in the vacuum system can cause not only problems with the heating and air conditioning, but other engine performance related problems as well.
  • Check the 2 vacuum lines at the fire wall on the passenger side for cracks and leaks. One goes through the fire wall and supplies the climate control solenoid array with vacuum. The other vacuum line controls the water cock.

There are also 3 vacuum lines that run back along the fender well to the vacuum canister. Check all of these vacuum lines for cracks and leaks.If they seem hard and brittle replace them. If you look closely at these lines you will find that all or most are color coded with a stripe. At the canister there are 3 vacuum lines, One with a blue, one white and one red striped line. Once you have identified both ends run a new line and pull the old one out. White goes between the manifold source and port M on the vacuum tank. This port should have a one-way valve built in to it. Blue goes between the water cock and the magnet valve on the vacuum tank. Red goes between the interior door controls and a live feed from the tank, sometimes labeled as F. Any remaining ports should be plugged. This may or may not fix the particular problem you are experiencing.

Click image for larger image.

Sources used on this page:

  • 1984-1988 Nissan 300ZX Factory Service Manual
  • Written by: Frank Zemaitis,
  • Water Cock Image by: PulseCode of Z31performance.com