A/C manifold gauge inquiry

So I'm looking to buy a set of gauges so I can fiddle around with the AC in my Nissan. Its an R12 system and I just happened to acquire some of that magical stuff. I see some gauges are for R-12 R-22 and R-502 systems. I understand the scales on those. But some gauge sets claim to also do R134a, which would be nice to have. BUT, the gauges on these sets are different and don't make sense. Of course it would help to have a manual. But do youse guys have a set of gauges for both types of systems or do you wing it. I've seen some R-12 sets that have adapter fitting for r-134a, but the gauge doesn't have a scale for r-134a. Sorry for rambling. It's past my bed time. Any advice is appreciated.

Scale? A pressure gauge is a pressure gauge last I checked.

They all read in PSI and BAR.

The main differences between the types of refrigerants as far as the gauges are concerned are how they hook to the service ports. Most gauges have r12 fittings with r134 adapter fittings screwed into them so they can do either or. The pressure ranges are pretty close to the same.

Kenny_McCormic wrote: Scale? A pressure gauge is a pressure gauge last I checked.

On both gauges, there are scales that show pressures for the various refrigerants.

Do you mean they show temperature equivalents for various refrigerants? I never look at those, a thermometer in the dash vent works better and I would be looking up the proper charge pressure for the system anyway.

It may not be a good idea to have just one manifold set, maybe have one for r12 and one for r134a. R12 uses ester oil and R134a uses PAG oil. It's hard not to get some of the oil in your manifold while it's hooked up. I have heard (second hand so not guaranteed accurate) that mixing those two oils results in some goopy mess.

On the scale thing, you can learn what psi the different refrigerants run at and just read the psi on the gauge. You don't need the gauge to tell you what psi you should be at.

Im not exactly sure what is going on here but if you need your gauges to explain to you how to repair an HVAC system, you dont need to buy gauges, you need to take an HVAC class.

Vigo wrote: Im not exactly sure what is going on here but if you need your gauges to explain to you how to repair an HVAC system, you dont need to buy gauges, you need to take an HVAC class.

Actually I had already thought of that and checked into it a bit today. The system in question I suspect is just a little low and just needs a boost. I wanted the gauges to check on its current state. I had a thread about doing a R-134a conversion a while back, but decided I want to stick with R12.

Look up Eric the Car Guy's videos on youtube. They're great for the basics.

I've got a set of old R12 gauges that are surplus to my needs. $25 + shipping and they are yours. PM me if interested.

IIRC those different "scales" are for R12 or 134a behavior equivalency, to give an idea of what to look for if you aren't used to working with R22 and R502.

Basil

I will be sending you a message.

I think my problem is about to go away. I took my truck to a local indy frame and alignment shop to have the front end aligned. They were working on a SCHP cruiser's AC. So I asked with they could help me out and they will. This shop is pretty low pressure, unlike the best AC shop in town that likes to bend your over the desk. Cuz they can.