Getting the AC to work in Dad’s 1979 280ZX
Once I got the fuel system sorted and some good tires on the car, I wanted to start driving it. However, the HVAC system would not blow any air.
I pulled the lower part of the passenger dash apart and took a look. I found a previous owner had totally butchered the fan motor wiring. Armed with the factory wiring diagram. I eventually sorted the problem. The main relay was missing so I substituted a standard five-pin relay and redid the messed-up wiring.
After replacing a blown fuse, the fan worked properly. Even the variable speed knob worked.
However, even with the fan working, there was no air blowing out the vents. It seemed that no matter where the control lever was set, all the vents were closed.
I began tracing the vacuum lines using the factory diagram and quickly located the problem. I found the line coming out of the accumulator valve was split. There was enough slack to just cut the bad part off and reconnect the line.
This worked fine for a week or so until the vents stopped working again. This time the trouble was the magnetic valve was not opening. I used a test light to determine that it was getting the correct signal, it was just not working. I removed the accumulator from the car and then removed the valve from the accumulator. After hooking up some test leads to a battery and some tapping I got it moving and working again.
Now it all works properly and is controlled by the control lever to choose which vent is active.
The next step was to get the AC compressor working. I used a test light to find that the low Freon pressure switch was stopping the compressor from engaging. I made a quick jump of the switch and the compressor ran with no funny noises. I decided it was worth a shot to see how it responded to a charge.
As I started to hook up the gauges, I noticed the system had a small amount of pressure. Since the car had been sitting for ten years or so, I found this a good sign. I decided to use a can from my stash and top up the refrigerant and see what happened. The gamble paid off as now the system blows cold air out the vents.
Getting my Dad’s 1979 ZX running again and driving my dream car.