Questions for Servicing R12 AC
 

I've done multiple search but could not find the answer I need, most of the threads are about converting R12 to R134, which I am not intending to do... so please help me out.

1. Would the normal AC manifold gauge for sale on the market fit the R12 port fitting? I know the R134 has the quick connect ones and R12 has the threaded ones, so I am not sure if I can use the ordinary manifold set to connect to the R12 fittings. (My dumb ass, figured this out, I think I can just use the adapter for R134 and screw on the current fitting..)
2. I am not replacing any components in the system, but I do plan to pulling a vacuum on it to see if there is a leak, then recharge the system using R12 or Freeze 12. In this case, do I need to add oil to the system?
3. From all the info I've seen, it looks like the can tab for R12 and R134 is different? Can anyone please confirm?
4. I have a JDM RHD FD, how can I tell what compressor it has? And the amount of R12 and oil (if needed) it needs? I think the nippondenso calls for 21OZ of Freon.
5. Am I blind or what, I don't see the AC/Heat service section in the FSM.. I know where the ports are which is near the fire wall behind the intake manifold, but which one is the high side and which one is the low side?

Any one who have recharge their R12 AC system, please chime in with tips..

Much appreciate it.

5. My US market '94 has the R12 system and it still works well. Its heater and AC system are covered in Section G of the 1994 Mazda RX7 Body Electrical Troubleshooting Manual, not the FSM. R134a systems are also covered.

It and other RX7 manuals and wiring diagrams, etc., are available free to download here: Mazda RX-7 Reference Materials

First off, good luck finding R12 unless you're scouring garage sales and flea markets or in the biz. I have 4 cans I saved from my '76 Corvette when I sold it 20 years ago, about $2 when I bought them.. And I'm keeping them since that's what's in my FD. That said, the can adapter on my R12 clamps around the top seam of the can and is then screwed down to seal and again to puncture. The R134 adapter threads directly onto the can, obvs to prevent system mismatch (and sell more parts!) and has the quick connect. My Corvette used to take one can per year, so very slow leak, so I never fixed it. I just EBay'd my gauge set, since I hadn't used it in forever, figuring I'd just use the sight glass in the FD if I leaked down. Do you have the recovery eqpt to reuse the remaining R12? The prices are astounding.

If the gauge set you're buying has this kind of connect (R12/R22), you should be fine. But frankly, you may have lost only enough R12 to prevent the compressor from starting. I'd throw a 12 oz. can in first. When you find it.

https://cimg2.ibsrv.net/gimg/www.rx7...540977d431.jpg

Nothing cools like R12 in an FD. It's like ice coming out of the vents.

You can get R12 on Ebay but you need an EPA license to buy. I don't know if it's still the case, I got my license a number of years back doing an online test - wasn't hard, did it on a slow work day. I've seen plenty of vintage cans for sale recently.

For the can tap, use a side tap -


They work on any can and actually work better than the original R12 can taps.

You can swap out the fittings for the newer quick disconnect fittings. I have heard that finding GOOD ones that don't leak can be tricky.

I don't know if you can still buy a manifold set for an R12 system with the OG fittings. I have one that I bought 20 years ago and I have to use a high side adapter with it to make it work. It may just be easier to convert the fittings.

Also, it may just be worth getting a can of R12 and shooting it into the system on the low side.

Another option down the road is going to R152a - computer duster. Works really well, will cool as good as R12 in our cars. Super long thread with lots of wisdom on the topic -

https://www.rx7club.com/2nd-generati...gerant-964688/

Note that thread is in the FC area and some of the stuff is FC-specific.

Dale

Ahh I see, I will take a look.

Ebay has some old stock R12 as well as Freeze 12, by the popularity and positive feedback, I might just go with the Freeze 12.

For the port, I think I can just buy the adaptor for R134 and screw them on there then should be able to use the gauge set that why.. I think.. But Ima have to hunt for the R12 can tab..

My compressor does kick on and AC is cool, but not cold, especially when outside temp is high or the car is stationary, so I am more leaning towards evac the whole system and put the correct amount of Freon in there. I dont want to accidentally overfill the system..

Freeze 12 from what I understand is a pain in the ass. I would do R152a before going that route.

With the system on full blast, look at the sight glass that's on the receiver/dryer near hte battery. If you see bubbles, the system is undercharged. If you add R12 in, you just add until the bubbles stop.

It would be worth having a manifold though to see at least the low pressure reading and also have a knob that you can stop/start and regulate flow of refrigerant into the system.

Dale

"My compressor does kick on and AC is cool"
Ain't broke. At worst you're low. Or maybe a blend door problem? <= WAG

"With the system on full blast, look at the sight glass that's on the receiver/dryer near the battery. If you see bubbles, the system is undercharged. If you add R12 in, you just add until the bubbles stop." ~ Dale

^^ This. R12 can tap and hose - https://www.ebay.com/itm/353433433822

For a R12/134 substitute I have been using the chemicals from http://www.es-refrigerants.com/ for many years.
They use to list the two desperate but the mixture is the same for both 12 or 134.

Which kind do I need to buy? I looked thru their website about compatibility, but I guess due to legal reason, they are not very clear if their products are compatible with r12...

sounds good!! thanks for all the info!

Thanks for all the info Dale, I looked thru the thread you posted, but does r152a mix with r12? or do i have the evac the whole system?

Short answer is you'll need to evacuate the system when switching refrigerants - mixing refrigerants is never a good idea and typically results in poor A/C performance.

Also, depending on what refrigerant you're switching from/to, you may also have to flush the system to remove the old lubricant and replace it with what's compatible with the new refrigerant. Refrigerants like R134A or R152A/duster gas are not readily miscible (sp?) with the mineral oil lubes normally used on old R12 systems, so when converting it's best to flush all the reused components and get a new dryer. Also the 134A & 152A refrigerants will tend to rot out the black O-ring seals used on R12 systems, so it's best to replace them all with the green HBNR O-rings which are compatible with all 3 refrigerants (R12, 134A and 152A)

I restored the A/C system on my FC (stock A/C system) and charged it with R152A duster gas, works great. Also restored the A/C system in my FD, but that restoration involved a mix of OEM FD parts and some generic A/C bits (all plumbing, dryer and condenser). I'm using R134A in the FD, and it works well - about 40*F air coming out of the vents on 85~90*F days. You can read about my FD A/C resto work in my build thread here, starting on post #12 - https://www.rx7club.com/build-thread...oject-1149941/

There's a LOT to know about AC, it can hurt your head pretty quick. I know a heckuva lot about it and there's still stuff I don't totally have the knack of.

That said, I would see if there's some way to get your hands on some R12 and charge the system back up. May even want to call around in your area and see if any shops stil can work with R12 or know someone who can do it on the side. That's hands down the least amount of work needed to get the AC going like it should.

Changing to a new refrigerant just involves a ton more work. As Pete said, you do need to change the oil and possibly the O-rings in the system which is a substantial job.

You can have the car converted by a shop to 134a but with the car as it sits you will be disappointed. 134a in the FD's system gets cool but not cold. To get it truly cold you need to upgrade the AC condenser - the "radiator" at the front of the car - to one that has more capacity and heat rejection. That starts getting into custom fittings and lots of fab work. Pete's thread will give you a good idea of the work.

If you lived up north where a hot day is 85 degrees and 50% humidity, a 134a conversion would be fine. I bet in SC you have swampy weather like we have in Pensacola with upper 90's and 90% humidity - you need a system that can really push out cold air.

The other alternative refrigerants (Freeze-12, ES-12, etc.) have been used by some with luck but I don't have first hand experience with it.

Dale

Any chance it may have already been converted? I'm sure if it was done by a pro it would be labeled as such. :dunno:​​​​​​​

Thanks Pete, I will def check out your build thread!

Thanks Dale, I will more than likely go with recharging it with R12 than switching to other refrigerant.

I dont think so because the ports are still the old R12 style port.