R12 amount?

[rpsharpe]

Does anyone know the amount of R12 to fill an empty A/C system on a stock 1986 CJ7 with a AMC 258 i6 / 4.2l ?

I know this is a good time to change to 134a, but I have R12 and am old fashioned....

 

[hdgapeach]

Three cans, maximum. Usually two will get it about right if it's not a total charge replacement. You really need to have a set of gauges so you can monitor the pressures while it's filling. If you're not sure of what pressures you need, a pressure chart ain't a bad thing to have. The ambient outside temperature affects the required pressures you'll be looking for.

 

[rpsharpe]

Roger, I have gauges. I need to repair system leaks first, vacuum test, then charge. I just didn't know how many cans I needed.
Thanks.

 

[hdgapeach]

Three ought to get it done, with some left over. You considered converting to R134A?

 

[wm69]

R134 in an OEM system took a little over 2 cans. I converted my OEM system. Worked great till I got a pinhole in the condensor. Gotta get that repaired and recharge it.

 

[rpsharpe]

Yes, I considered change to 134. I figured if this doesn't work, then I'll spend the $350 to convert.

 

[hdgapeach]

WOW! Didn't realize it was so expensive. All the conversions I've done amounted to changing all the black O-rings out to new ones that are 134 compatible. I've only had to change out one accumulator that I remember. It needed changing before the conversion.

I don't know what all is involved with the Jeep conversion. I've only swapped Fords over.

 

[rpsharpe]

Good point...

That price was from a mechanic I respect and has always given me an honest price. Receiver/filter & O-rings make sense - I wonder what else is included in the price of $350???!??

 

[wm69]

Ummmmm. the factory CJ doesn't have O rings in it. Flanged fittings.

When I bought the Jeep it was missing the line from the condensor to the compressor. I replaced it and simply vacuumed the system down, put the R134 fittings on the back of the compressor, and charged it. Blew ice cold for about 5 years until I got a pin hole in the condensor.

 

[rpsharpe]

Nice! Now I have my next project. I have gauges and a vacuum pump.

I knew the hose I was replacing (from receiver/filter to evap) had flanges, but didn't think about the other hoses since they were already replaced. I hope it has no other leaks.

BTW, I found an small, old repair shop in Allentown, PA (Avenue Motors) that made the hose for me while I waited. They had all the old R12 fittings in stock which was nice because I replaced the service valves on the compressor as well since they were not functioning well. I'm just waiting for the low pressure switch to come in the mail and I'll put it back together and test for leaks.

Thanks for your help.

 

[wm69]

I would flush the system out while you have it apart. I didn't do that with mine, but no telling how long it had been left open. I know I got lucky with mine. Now that I know all the components work when I take off my condensor to have it patched I'm going to flush the rest of the system out and refill with new oil and R134.

 

[hdgapeach]

Late reply, I know. I've been out of town a couple of days.
I was assuming the extra expense was due to compressor compatibility or something. Never heard of that, but I reckon anything's possible.

Good info to find out that there's only flange fittings and no O-rings. Flush system, replace accumulator / receiver-dryer (whatever you want to call it), tighten it all up and give it a charge.

When I was turning wrenches for Mazda, air conditioning was a dealer installed option. We never vacuumed the systems down after install prior to charging and not once did we have a problem. Called for three cans. Two for the charge and one for the tool box ! Had quite a stock of "Freon" for a long while.

 

[rpsharpe]

For anyone following this thread or who will need it in the future:

A stock A/C system takes three cans of R12.
Use a manifold gauge set and pressure/temp chart to charge.
Replace receiver/drier and low pressure switch (both cheap)
Jeep Air is a good source of info and will make hoses you can't find.

Finally, while I used R12, if you are doing any A/C work now is a good time to convert to 134a. Your CJ likely has all flange fittings (no O-rings). Call Jeep Air and they will tell you what you need. I decided to use R12 because I had it....a search on eBay reveals R12 I selling for $30-$40 a can. Ridiculous....