arke

I have a 88 13B. The A/C compressor actually works but the air is only slightly cool. It needs to be recharged. It still has some old R-12 in it. Has anyone ever converted their system?

professionalpyroman

I converted my 89 over this last spring. First question is how much work do you want to put into it, and how much skill do you have? Second question is do you want to get the R12 system back up and running correctly instead of converting it as R12 is more efficient for your equipment?

arke

If I were able to get some R-12 I would simply charge and go. Unfortunately it is very hard to find R-12. I have no problem changing dryers O rings and even the compressor. However in the in order to change the condenser coils I have to disassemble the entire dash. I don't want to go there. I am not expecting ice cold air, I just want it to be somewhat cool to take the edge off of real hot days. This is not my everyday car. Only a Sunday Funday car. If you have any experience converting the system. Please let me know what new parts to install along with the typical valve replacements.

professionalpyroman

Good deal. Well, even though you don't want to take the dash out, I would still recommend it to do the job completely. It's not too bad, about 8 bolts I think, 2 on each end and 4 in the middle. Then just disconnecting wires until you can remove it.

These are the steps I did for mine. I'm writing them up this way so that this thread can be useful to anyone wanting to know what I did.

1. The first step is to depressurize your system. Dispose of the coolant in whatever responsible manner is required by your state.

2. Next, gently disassemble the system. These aluminum lines like to get stuck together over 30 years. Use brake line wrenches instead of open end or crescent wrenches to undo the fittings. Penetrating oil won't help with any corrosion between the aluminum lines and steel fittings, but it may help things stay moving once you get the fittings broken loose.

3. Remove all components of AC from car, including compressor, condenser, dryer, evaporator, anything that contained coolant.

4. Clean all tubing and coils using an evaporating cleaner, parts cleaner, alcohol, whatever, so that the mineral oil from the R12 system is removed and no residue is left inside the tubing.

5. Buy a new dryer.

6. Either buy a new compressor, or rebuild the one you have. The compressor I had was a Nippondenso 10p15c compressor. If you have a different one, you may have to do some more research. This portion is made to reflect the work I did on my compressor. This compressor is full of mineral oil. The FSM says to drain the old oil and put new in, but since mineral oil is not compatible with R134, I had more work to do. The oil compatibility chart for Denso compressors can be found here DENSO Auto Parts | Products | AC Compressors. It listed mineral oil as the oil for my compressor. However, oil used for the R134 systems is listed as ND8 which is a PAG oil, and is required in twice the amount for the compressor. This is a "close enough" guess, so continuing on from here you are responsible for your own system. The ND8 oil is equivalent to a PAG 46 oil for R134 systems and is readily available.

Following this, I disassembled the compressor using the instructions in the FSM found here RotaryHeads.com - 2nd Gen RX-7 PDF Technical Manuals FC3S. I did this in a clean environment so I didn't contaminate the inside of the compressor. I cleaned all the individual parts, removing the mineral oil. I replaced all the old BNR compressor o-rings with new HBNR o-rings, found here Arizona Mobile Air, Inc. | Automotive Air Conditioning Parts & Equipment and reassembled. I poured in the amount of ND8 oil used for the R134 system setups, using the closest guess from the chart, about 4.1oz.

7. Reassembled system using HBNR o-rings to replace the old BNR o-rings using an o-ring kit bought at O'Reillys. Made sure to use lubrication when reassembling tubing joints. Also put oil in new dryer as specified in FSM

8. Reinstalled dash

9. Installed conversion valves for high and low pressure ports. Evacuated system using vacuum pump and gauges from Harbor Freight (take a coupon before you buy them). Left under vacuum for a week to check for leaks (daily driver, so gotta have AC).

10. Charged system to R-134 operating pressures using gauge readings and procedures per manual.

Done.

Also, if you are having blower fan problems, there are threads on here about rebuilding the fan amps and replacing the driver transistor. I did it all together and this was worthwhile to me. This is what I did for my car and it worked. You do however take responsibility for your own vehicle here, as this is a modification and not a repair. Good luck.

arke

That is the "Full Monty". I don't like doing things half way, and it sounds like this may also be my approach. I can't thank you enough for going through all the description.

NCross

iTrader: (18)

The shops I've worked at do conversions all the time without the need of replacing any parts (as long as the system functions and has no leaks). Put R134a adapter fittings on it and charge with 10% less than the factory spec for R12. If I were you I wouldn't waste my time DIY with AC in a can crap as it will not pull a vacuum (meaning you will always have air in the system and not the proper amount of freon... Have a shop do the work because you will want a good AC machine to pull a good vacuum on the system and add exact amount of oil and freon to the system. As both a service writer and a technician I would quote the job out at about 1.5 hours plus freon and parts. so depending on shop rate between $2-250.

professionalpyroman

NCross quoted you an accurate shop price if that is an option for you. That's what it cost the local shop to service my R12 system before I converted it. The compressor seals blew shortly after that service, so that's why I decided to rebuild the entire system. The R12 service is definitely a good route to go. If you were to rebuild your system using the steps I described, but stick with the required mineral oil as a lubricant, you can have a shop vacuum and charge the system with R12 for the $250 and have a more efficient AC. However, given the systems are 30 years old, would still recommend new o-rings and dryer.

scathcart

Relisys190

iTrader: (4)

My car has 152a and it blows ice cold. Duster gas. Yes duster gas and 3oz of ester oil. Evac the system first and go from there.

Relisys190

iTrader: (4)

Great thread works perfect!

NCross

iTrader: (18)

I'm sure 152A works close to 134A, but too bad it's mildy flammable. More-so than 1234y. You still need to figure out a way to vacuum the system or it will not be up to its full potential. I have had several converted systems (three of which being RX-7s) and if they are leak-free and function fine otherwise you will still get cold air on a hot day. Just change the fittings and gas it up with a real AC machine with 10% less charge than the under hood sticker says.

scathcart

Relisys190

iTrader: (4)