AC Question

[Hank857]

Hello, 1st post here and need some help.

My son has a 90 300 TT ZX and the AC has quit on him. Compressor clicks on, fan blows but no cold air! Hooked up a can of 134 to it the other day, it did take a small amount but thats it. The AC was workin but we have been trying to hook up a couple of things and I need to know IF the AC vents are vacuum controlled?

He installed a short shifter, we added some driving lights and we are trying to tie into the boost system for an AM gauge. During the light install we blew a fuse and had fun trying to find the box and then we ran a wire under the dash and that is why I need to know if we may have dislodged a hose someplace. Also blew a fuse when we had the radio out for the shifter install! So again thats the question, how are the doors actuated on these cars?

Also where is a good place to hook into for the boost gauge? We found a vacuum source but that is all it does show vacuum no boost. Saw a picture in the files here that shows the boost line to a sensor on the driver side and it comes apparently from both turbos. Is that the place to T into?

Again thanks in advance, I am sure we will be back.

[es.biggs]

For the AC, try getting pressure readings for the low and high sides. Separate readings for before the car is started, and while the car is running with AC on.

[marty1mc]

First, Welcome. Second, the AC control system is electric not vacuum. There are 4 motors that control air flow and water (for heat). One is a mode door motor and controls where the air comes out, def, vent, floor. It is located on the heater box (up and to the left from the accelerator pedal). The next two are air mix motors, they are located under the heater box. They control the air flow through the box and shut off the coolant from entering the heater core. (The heater box needs to be removed to get these out. They are also no longer available from Nissan). The last one is a vent door motor. It controls fresh/cabin air and is located on the right side of the car, attached to the fan motor box.
I see you added R134a to the system so I am assuming your son's system has been converted? Did you add it to the suction port? The suction port is the port that is on the large tube on the right side of the engine. The small tube is the high pressure side and NEVER try to add there.

If you suspect the air isn't getting through the system, then I would look at the ac box. There is a resistor block that controls the fan motor speed that is mounted to the side of the box. It is located on the passenger side, just under the glove box. You may want to remove the glove box to get to it (not hard). The pull the resistor block out and either get a temp reading on the expansion core or feel it by hand to see if it is cold.

Here is a link to the online Factory Service Manual. It has an AC section with diagnostic procedures you can run to help narrow down the problem.

http://www.300zx.co.uk/cgi-bin/manual.cgi

[Hank857]

OK thanks for the replys. As to the hi/lo the guy that checked the system was an AC guy said it all looked OK.

Now are the electrics hooked to a particular fuse? I have ordered a manual on CD but wont be here for a week or so, and as I indicated we had some blown fuses to mess with. The AC was working well prior to the fuses getting blown so that now leads to the question, where are these diverters fused at?

Thanks

[marty1mc]

Here are two diagrams, one with the wiring layout and one that shows where the fuses are located...

http://www.ttxtz.com/tech/lee/Wiring-Co ... _32-39.gif

http://www.300zx.co.uk/tech/fuse-translation.htm