I was test driving a 2nd gen (an '88 I believe) with a buddy of mine a month ago or so and every time he would floor it the vents would start blowing heat. There was plenty of coolant, so I don't think it was related to there being any kind of shortage of that. He didn't buy it, but I am curious to find out why it did that because my '85 300ZX does the same damn thing. Anybody else have this problem?

 

^ this hasn't happened to anybody else?

 

Could be a couple of things:

loose screw in the logicon (sometimes the face looses a screw when the plastic get old) and it shorts out the temp sender for the air mix motor. Replace or rebuild Logicon.

Loose connector to air mix motor. Re attach connector properly.

Aftermarket radio wires routed incorrectly and a caught on air mix motor and/or accel pedal.fix wiring run