I'm going to be installing a new AC compressor soon,
should I convert the system to R134 or use R12 (which I have a supply).
The guy that will be charging the system after I change the pump says
I should just use the R134 because it's easier and the performance will
be identical anyway.
What would you guys do?

 

R-12 for sure, it will run much colder than r134.

 

I agree with Montana2x2 r134 is not as efficient as r12 and you will lose some cooling, I don't know if cooling or ease of future service is your main concern around here it is getting hard to find someone that will service r12 anymore.

 

If you go to the R-134a you will have to flush the system and install the new valves compatible with R-134a and like previously posted you will loose efficiency..

There is a new refrigerant compatible with both R12 & R134A it is called ES12a. Here is a link to it:

http://autorefrigerants.com/co00033.htm

 

I installed a new compressor on my 91 and converted to 134a, the compressor lasted two days. And the conversion was "by the book". I suggest sticking with the R-12 as long as you have a supply.

 

I would go with the r134a conversion. If done properly (which isn't hard) it will do a fine job of cooling, and will be cost effective in the long run as r12 is very expensive if you can find any. As for r134 being less efficient, the opposite is actually true. The only place this can be a problem is if the condensor is marginally sized, but this won't be a problem on your truck. I have done lots of r134 conversions and know from experience that they will cool just as well as r12, maybe better. I would steer clear of "drop in replacement" refrigerants because they are all blends of multiple gasses which travel through the system at different speeds, and bleed out of the system at different speeds eventually leaving only r134a in many cases anyway.

 

I switched to 134a about 10 or 12 years ago and it worked fine until yesterday, when a line blew. Got one coming so I get to do it again.

 

I would stay with the R-12, DICHLORODIFLUOROMETHANE.
That is what I have in mine and my register temps usually run around 20* but it has the ability to get much colder.

I even have the owner/ tech of a local AC repair where I get some of my parts scratching their heads.



There looks to be plenty of it on Ebay

http://cgi.ebay.com/30lb-R12-R-12-Fr...3A1%7C294%3A50

R-134 is bad in traffic, without an auxiliary fan on your condenser the head pressures can get excessive and blow the relief on the compressor or stress the hoses until something blows.

Also remember that when a line blows or anytime the refrigerant is vented rapidly the oil will leave the system with the gas, you need to flush out all of the oil and replace the factory amount.

I have tried a lot of R-12 alternates that all claim to cool better than R-12 but I have personally never gotten lower temps than with R-12, so far the best drop in I have used is ICOR.

Jim

 

Holy crap thats cold a/c Jim... I wish i could feel it through my computer.

they sell R12 on ebay. I don't know why people say its hard to get....

 

Well, for starters that particular link is local pick-up only in Chicago, and you need an EPA cert (which I assume most people don't have).

Is there any on there that will ship/sell to CA, and not require a cert ? ( I Cant search from here)

I would gladly pay $100 for 30lbs, and switch back. Our systems take what... a little over 3lbs to charge ? Shops around here wanted over $300 to do it.

In my limited experience R12 has always worked better than 134. Even our newer cars that came with 134 from the factory don't seem as cold as a properly functioning R12 system.

 

C3H8 (propane) works pretty good.

 

What Jim Lane said... Head pressures are what ruin R12 converted compressors and there are a refrigerants that you can use with lower pressures than R134A.

This refrigerant works well and is compatable with the r12 system, no flushing etc.

http://autorefrigerants.com/co00033.htm

 

I'm very confused by Jim's temp ??? I thought sub-freezing would return liquid to the compressor which isn't compressible. Is that thermometer broken?
Does you evaporator freeze? If that's R-12, what's your low and high side pressures when you indicate 5 F??

M

 

Just last week I had to replace my A/C compressor because the front bearing seized, I bought a brand new one from Napa for $374.49 plus Freight Ouch but I needed my air conditioning.

I also replaced the receiver/ drier.

Here is a Pressure Temperature Chart this will tell what the pressures will be at any given temperature. See at 80* ambient temperature R-12 should be 84.2 PSIG





See what I have static.



Now here are my pressures @80* ambient with the evaporator blower on High and only the engine fan was the only ram air to the condenser.

At this time I was not checking the vent temperatures.



This is interesting, the factory charge should be 44 ounces of R-12, and I charged the system only until the sight glass cleared. It was charged at 2 pounds or 32.0 ounces.



I later went for a ride and checked the performance; this was around 8:00 P.M. after a short ride at 75 MPH.

The blower was on the second click down ,High for you or only Med for because I have my blower on a full power relay.



Today it was probably 100* and after a couple of miles the inside vent temperature would only get down to 25* so I need to check and adjust the charge and see if I need a few more ounces.

I am going to install an electric fan on the condenser so I can have consistently cooler temps in slow traffic.

Yes the thermometer is accurate and is calibrated using the ice point method.

Jim

 

What is confusing?
Freezers and Chill Plates will produce temperatures well below freezing and they still have gas returning to the compressor.

No my thermometer is not broken, I have several and they are all calibrated using the Ice Point Method, if you are not sure what that is check this.

http://www.myflorida.com/dbpr/hr/for...s/5030_062.pdf

Yes my evaporator has occasionally frozen up but that will usually only happen if I have the fan on low speed, it has done this maybe 5 or 6 times that I can remember.

Yes it is R-12 and I would have to go back and find the pictures from the last time I charged the system to see what the pressures were, but in the post above it would produce temps of 10* with about a 70 MPH ram air.

Also if you have read my post you will know that I have removed my Cycling Switch so I can control the compressor from not cycling off when it thinks it might ice up, I can push the system to its lowest possible temperatures. It seems that I control the ice up with a constant flow of air over the evaporator coils.

If I am on very long trips we will usually be wearing a jacket in the cab because it can get uncomfortably cold and I will take it off MAX A/C and temper the air with the heater.

I also find that I have to turn the side vents away from the steering wheel because they will freeze my knuckles as an added bonus I can direct the left hand vent onto my drink holder and I will always have an ice cold drink.

I am thinking about installing an adjustable thermostatic switch to the clutch circuit with the capillary bulb inserted into the evaporator coil so I can adjust the temperature I want and make my freezer more user friendly.

Also for those of you who convert to r-134 the amount of oil in the system is critical, not enough and the compressor will suffer and too much you will get poor cooling no matter what the charge.

My new compressor took 2.0 ounces after I drained out the oil that it was shipped with.

Jim