austinrx7bill

Hi all.

First, the naive-sounding title notwithstanding, I do know what I am doing with auto AC systems -- but only R134 systems. I have done everything from a complete flush to compressor, expansion valve, receiver-dryer, condenser, evaporator and sensor/switch replacements on probably a half dozen cars, just never one with R12.

The RX7 (82 GSL) I bought 18 months ago has an AC system. I am assuming it is original and that it hasn't been converted to R134 (there is no label indicating such a conversion).

When the AC is "on", the compressor clutch engages and the temp drops an imperceptible few degrees (no more than 5), so there is a little refrigerant in there otherwise the pressure switch would keep the clutch from engaging, right?.

According to the label, the compressor is a Sankyo-575.

Both the low and high side ports are on the compressor itself rather than on the suction and pressure hoses as is more typical of "modern" cars. Neither are marked.

It looks like both ports are threaded schrader valves, however, one of the ports (see pictures) appears to have an adapter on it, perhaps to allow it to be filled with R12 or R12a (or R134) using an R134 quick connect.

Installing this R12 threaded-to-R134 quick connect is typically how R12a (propane based) refrigerants are filled (also, when systems are upgraded).

Both the threaded schrader and the threaded-to-quick connect ports have blue "low pressure" dust caps on them, so that's no help in figuring out which is which.

If I had to guess, the port with the quick connect adapter on it is the low port, but before I blow myself up by putting high pressure into a can attached to the wrong port. I am just hoping for some verification on this forum in case someone knows positionally, which port is which.

Thanks in advance for any help.

midnight mechanic

blue is low, it is cool to the touch, it is where you stick the freon in

rubber gloves prevent frost bite, safety glasses and squeeze bottle of soapy water too because there is always slight spray when connecting/disconnecting

84rtaryrcket

it appears the compressor is labeled it looks like the "s" designates suction(low side) the "D" designates discharge aka the high side. so looks like the conventional quick connector is the suction line.



im almost ready to tackle my AC next, r12 currently ill be swapping over to 134a. i can live with it robbing a little power when i can keep cool on a hot summer day!

austinrx7bill

Aha, very good observation, Mr. Holmes.

I took that extra picture of the ports from a slightly different angle to try and capture both the stamped S and D.

Glad you caught it. And agree with your interpretation. Does your RX7 have the same compressor?

I finally got my gauge set back from my brother and the low (blue) hose screws right onto the "S" schrader valve.

Under the assumption that the quick connect adapter is R12 to R134 quick connector, I tried to get both the high and low side quick connect on that adapter just to see if one fit and the other didn't, but that darn insulated suction hose is in the way and I didn't know if it was soldered onto the aluminum "clamp" that secures both the suction and discharge pipes to the compressor and didn't want to bend it.

Does anyone know if those pipes on the aluminum clamp are fixed or whether they'll swivel/twist a bit in the clamp?

And do you have some sort of part list or other guide that you're as a how-to for the R134 upgrade?

84rtaryrcket

For me I'm going to pressurize the system with nitrogen to leak check with bubbles or my leak detector. Then I will replace all orings and the receiver drier. And if I have to, the hoses although I hope I don't have to. And I will buy the conversion adapters to go from r12 connections to 134a quick connects.

Then once I have flush and leak checked the system and replaced the accumulator and got all the old oil out I will replace with the appropriate amount of refrigerant oil and 134a. Then smile when it's 90 out and in ice cold 😬

Oh i do hvac for a living so this is a walk in the park.

austinrx7bill

what about expansion valve and pressure switch? I thought those had to be replaced as well? Guessing that the expansion valve is at the firewall but inside the engine compartment, haven't traced the receiver/dryer yet.

I am a master at flushing AC systems (super OCD about it, so that doesn't scare me, though I have never flushed compressors but rather always replaced them.

Given the r12-to-R134 adapter on low side, I am now now sure whether the system is still R12 or the previous owner upgraded it to R134 (and no way of tracking him down I don't think), so I think as a first step I am going to try the RedTek R12a, propane based, allegedly compatible with both R12 and R134, and see what happens.

84rtaryrcket

The expansion valve is cheap enough I will probably change that too

austinrx7bill

But the new expansion valve will have to be one for R134, not R12, right?

And I thought that R134 operated at a higher pressure than R12 so the pressure switch needed to be changed as well?

t_g_farrell

iTrader: (1)

It probably has 134a in it. I would refill with 152a (DustBuster), its the same cooling curve as R12 and cheap, cheap, cheap. I always replace the dryer, all washers with green viton washers, expansion valve is a good idea, and hoses if an old car, completely evac everything out of the system, reassemble and pull vacuum and let it sit at least a couple of hours or overnight. Then fill. The pressure switch will work fine for all these refrigerants as far as I know. Make sure to use mineral oil or something that won't interact with the 134 at least.

Jose Mercado

do you know what other compressor is compatible to this one? my compressor is also converted over to 134a, but I need a new compressor, and I cannot find one like this, meaning a sd 575.

midnight mechanic

"It probably has 134a in it. I would refill with 152a (DustBuster)"....sounds like a good idea, but how do you make the connections?

dustbuster for keyboards available at Office Depot and Staples? Right????