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 vac 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 vac tank.Red goes between the interior door controls and a live feed from the tank, somtimes labelled as F. Any remaining ports sould be plugged. This may or may not fix the particular problem you are experiencing.

Sources Used on This Page: Writen by: Frank Zemaitis, 1984-1988 Nissan 300ZX Factory Service Manual,