How about vacuum leaks? On my '87 the air would turn to defrost with heat because of a vacuum leak usually at the reservoir.
Randy
stang1 wrote:
>
>> I have a problem with the automatic climate control in my '96 300ZX.
>> When I first take it out of my garage, the A/C blows ice cold and
>> gradually warms up while driving... the air blowing out of the vents
>> then seems as warm as the outside air within 10 minutes. I suspect
>> that the heater and a/c are actually running together, and that the
>> time it takes for the air to become warm is the normal time it usually
>> takes for the heater to warm up.
>
> Try warming up the engine with no A/C and then turn it on. it it still > does
> this "cools for 10 minutes" cycle starting with a warm engine, you could
> have a bad suction throttle valve.
>
> Otherwise like someone else sugested, perform a diagnostic check of the
> climate control system. I've seen very few problems with them but seen a
> BUNCH of bad suction throttle valves.
> --
>
> Steve
>
>formatting link