Guys, I need to know what type of ac compressor does a 1978 280z have? I have a 280z and it has the original ac compressor but I don't know the brand of it. Thanks

If it's factory AC, it's a Hitachi SWP 123.

Thanks for the quick reply, this is the over view of the compressor http://www.ackits.com/diagrams/Hitachi.pdf. Thanks, I'm trying to add some more r12 to my ac but don't know wich side is my low side, i'm also trying to get some r12 gauges, i have r134 gauges but not r12. Thanks

On those compressors the low side port is on the back and the high side is on the top. Gauges are gauges. All they do is read pressure. What you need is R134a adapters that screw onto the compressor ports. That would allow you to use your gauges you have.

Yeah, i have those adapters but when I open of the manifolds for the low and high side the low side goes all the way to the right and the only gauge that reads is the high side, also the r12 gauge I belive is different on the actual readings. Some one told me that if I used a r134 gauge on a r12 that I could mess up the r134a gauges because of the higher pressure that r134a has, but i'm not so fimiliar.

sblake01, my question is how much pressure should I expect to see from the low side and the high side using the r134a gauges? Thanks

I can only approximate because there are factors like ambient temperature, engine RPM, etc., but generally I'd say 35-44 on the low side to roughly 200-225 on the high side @1500 RPM. The minimun capacity of that system is 1.5 lbs and the max is 2.0.

Thanks sblake01 for all your help, would you happen to know why my ac gauge on the low side goes to retard when I open both the low side and high side on the quick connects but it will read fine if I close the high side from the ac gauge? Maybe i'm doing something wrong? Well what i'm doing is first I connected the adapters to the compressor and yes I had the low side and high side correct then I connected the ac gauge quick connects to the compressor and I open them up from the quick connects and then I open up the valves from the gauge to read the readings. I know that when I try to charge it I should close the high side from the ac gauge. Well sblake01 if i'm doing something wrong please let me know, I just have to get it working because its hot here in texas.

dcruz, just use sblakes comments in #7 as a guideline and not worry about opening the high side on your gauge. Generally, there is a 10:1 ratio (High:Low) - so stay in that range and you'll be fine. TIP: When you are checking/adding refrigerant in extreme ambient temps (like here in Texas), get a garden hose and wash down the Condenser with engine the running. This will dramatically lower the 'Head' pressure or Discharge pressure allowing for better suction. Just watch the pressure and don't over do it!

Andrew, I think the 10:1 ratio would be more applicable in a R134a system. It's a little lower like 7-7.5:1 with an R12 system in my experince. I have a big shop fan that I place directly in front of the car when charging in hot weather. dcruz, like Andrew said, charge on the low side and check your readings with both valves closed. I don't ever open the high side valve on the changing manifold with the engine running.

sblake01, when you say to check my readings with both valves close do you mean the quick connects or the valves at the actual manifold? Thanks

The valves on your gauge set.