Hi. I have a small issue with my a/c in my '94 zx. Every thing works great, the climate control dash pod is excellent. Yet when i push auto/aircon the compressor wont enguage. I can short the compressor relay in the engine bay and it enguages fine. is there another unit or relay before the one in the engine bay? theres no signal to the a/c relay to energise it from the dash pod. If i overide the relay and get the compressor going, still no cold air and the system is charged with gas..... i assume theres more to it than rigging up an external relay and switch? any help would be appreciated, i cant find the wiring diagram anywhere online
The air conditioner amplifier may be faulty (the Aircond. computer). There is also a fuse under the bonnet near the relay for the air conditioner. Shorting out the relay so the clutch engages will be enough to blow cold air (as long as you also have the blower going (just checking that). Failing that, then you may have other issues such as a buggered compressor or a blocked tx valve. My Air con amp (computer) is buggered, and I have a separate cabin mounted switch that creates a path to earth for the relay. and that works fine. You may find some benefit in this thread http://www.aus300zx.com/forum/showthread.php?t=280337&highlight=aircon I ended up getting the tx valve done, but also had a faulty compressor. I got mine fully rebuilt for A$605 + install. Expensive task at the end of the day. All up over $2k to fix, but now it blows at down to 3 degrees
Thanks for the help pexzed. It definatly wont blow cold air with the compressor going. and the system is charged. So........i might pull out the dash (f*%k what a pain that is!) and get a fridgy to check the tx valve etc.... being a 1994 mode i guess an issue like this could be expected. Does anybody know where the a/c computer is located? im guessing that there must be a faulty valve or amplifier, i am not sure if the valve is electronicaly controlled or thermaly.
2nded ... what pex said also check the low pressure switch just behind front bumper (right behind drivers headlight. That can cause probs like you have... I, like Pex (I think either Pex did it first and I followed or vice Versa) bypassed the climate control of the aircon with a separate switch. Its actually not that bad a mod as it stops the climate control automatically engaging the aircon compressor (which robs power/economy).
You can get the airbox out without pulling the dash. You'd be better off getting a 2nd hand airbox with a known working tx valve, (from a car that had a working air con) The tx valve units are not serviceable in the Z32, and genuine replacements are $400. By definition, a TX valve means Thermal Expansion valve, it has no electronics. The amplifier is tucked up behind the centre console dash facia and on the drives side from memory?? correct me if I'm wrong
Got the issue sorted if anybody has had to bypass the relay and setup a seperate sw to run the compressor. A common part that fails in the aircon is the low pressure cut out sw, by either renewing or bypassing that pressure sw, the entire system will funcion normaly
Just thought I'd provide a update on this thread, covering a recent aircon problem that I have had sorted. On a drive back from Melb on a stinking hot day some months ago, the aircond just died within a second - fans and electrics all working, just no cooling. After taking the Zed to about 5 firms around ACT/NSW, none of them wanted to get involved without going down the "convert to R134a" route, with the consequent many-dollars, many-hours attached. So, I finally tracked down an excellent tech who would work in the system without conversion, is this how it went. Turns out, the air-con compressor wasn't being fired. When we bypassed the relay, we found that the front pressure valve wasn't letting the compressor start. When we bypassed that, we found there was no cooling, even with a compressor going. So checked further, and there was no R12 gas left. Then when checking leaks using a nitrogen pressure test, we found a blow-off valve had indeed blown off. So he replaced the blow-off valve (ruined BTW) with a plug, so it can't blow off in future - in his opinion, the pressure values already in the system should provide all the protection required. Finally, he found that the air-con thermatic fan had seized up and wasn't able to spin at all. So the real story is that the thermatic fan had seized, which caused pressure to build up in the system due to insufficient cooling at the front condensor (which turns the gas back into a liquid, reduces pressure, and send cold into the cabin). Being a 42deg day, the pressure built until the blow off value blew, releasing all R12. Then the front pressure value worked by shutting off the system. Then the air-con computer worked by not allowing power to the relay to fire the compressor. All good stuff, yeah! Prior to filling the system with fresh drop-in (for R12 systems) gas, we pressure tested again. It went to 380psi, which for a 25 yo car, is better than the pressure that can be held by newer/expensive models. So, whilst he fixed the air-con and regassed it, I still have to replace the air-con thermatic fan - which I can do. Sometimes, doing bypasses for switches and electrics may not be the right thing to do.
