yumyum1667

I need to replace the long hose that connects from the compressor all the way to the front of the car. While I am in there I am considering just going ahead and converting to R-134.

R-12 is getting harder to come by through my mechanic buddy.

How difficult of a job is the conversion? For now I would rather not spend huge bucks on the AC upgrade. I only drive on the weekends so I don't need it to be ice cold all of the time. August does suck in the south though.

UberXY

Just replace all the o-rings in the system ($10) and then make sure you evacuate and flush before refilling.

I just went back to R12 from R134a on my '84. Cools a little better.

R12 is still widely available, even on ebay.

rusnak

The two types of oil are not compatible. You should also change the receiver dryer, the valve fittings, and possibly the expansion valve. 134a does not work as well. Try to find R12 online.

whalebird

Simply evacuate and recharge with 134. Do not fool with all the o-rings unless they are leaking, the drier, and exp. valve all will work fine. 134 is not as efficient, and r12 is these days may be recycled which is bad. There are oils redily available that are compatible with both freons and should be used upon conversion.
I may get flamed for this responce, but I have it on the highest authority that this is the way it is done; and I have done these conversions for over a decade with no problems to date.

Makmov

As stated not that hard to do, but on the earlier 911 for 134a I beleive you do need to add an expantion vavle, which is non existant on a 911 originally.

whalebird

Oh yes. A compressor, and an expansion valve (otherwise known as a restriction) are the two principle componentrs in an AC circuit. All 911 AC systems have an expansion valve. On the earlier cars it's next to the evaporator inside the smugglers box.

Makmov

I guess I was under the impression that the early non factory air didn't have an expansion valve. R134a runs at more pressure... maybe I am wrong.

rusnak

I *think* the expansion valve might have a smaller orifice on a 134 expansion vslve.

I do not recall if my R12 had a larger valve, but I do know that I have a 134a valve on there now. What happened is that my conversion did not work, and after several trips to different shops, I bought the equipment and figured it out.

So, I don't recall what originally was on there. But there was a lot of kludge in there plugging things up initially, that I had to flush out. I lost a few r/d and x-valves during the process.

Makmov

the kludge usually comes from stop leak.

If your R12 system is working I'd just spend the money to put R12 back in. It runs lower pressures and is a lot more efficiant and we all know how these 911 are. They system is designed just a little too small to be really effective.

So what you end up with a lot of times is a system too small for R12, and you put 134 in it and it's not as efficient so it doesn't work as well, and then run 300+ psi that will find every weak spot in the system.

If you do have a bad R12 system that needs major work just do a full proper 134a conversion with a high effeciency evap. new drier because that is where all the crud collects, and then you will like find the balist risistor has failed.

rusnak

makmov, you're probably right about the 134. If I were to do it over, I'd stick with R-12 and just hover the ebay, craigslist, etc ads.

I was cleaning out the farm tool shed two days ago and I found a box of R-12. So it's going into the SC, which still has the old factory bits on it like a time capsule.

I think the kludge might have been old junk that was not properly flushed out, or whatever. I didn't use stop leak. In fact, I only buy the straight 134a, not the seal conditioner crap, etc etc.

yumyum1667

Thanks for all of the advice. I spoke with a local shop and they also suggested sticking with the R-12 which still seems available with some digging.

The shop also mentioned Freeze 12. Is that a good substitute?

Ed Hughes

An expansion valve, or a capillary tube is one of the 4 major components of a refrigeration system. It's what turns high pressure liquid into low pressure liquid going to the evaporator. But, I've never heard of a cap tube in a car's a/c system.

rusnak

There is a capillary tube that goes to the evaporator, but it closes the switch for the compressor. Entirely different obviously from an expansion valve, which will clog if there is any fluid which contains solids. The idea as I understand it, is to have droplets at the expansion valve, and gas after that, in the evaporator tubing.

Ed Hughes

That is a thermostat not to be confused with a capillary tube metering device. Yes, the part you describe uses capillarly action to work, but is apples and oranges to the one that goes on the system. Again, an expansion valve or a cap tub will take high pressure liquid to low pressure-then its on to the evaporator where it turns to low pressure gas, thru the compressor to high pressure gas and then to the condenser to become high pressure liquid. 4 stages of refrrigerant in the classic refrigeration loop. I've sold commercial refrigeration for a long time now, the only time I see cap tubes to meter refrigerant is on low-end or budget commercial refrigerators. Domestic units are prevalent with this too.