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My truck has the original Ford R12 AC compressor and was converted to 134 approximately 5 to 7 years ago. It worked "OK" but never really got cold. The system was opened last year when I completely disassembled the truck however I did take care and protect it from dirt prior to reassembly. Now with summer really turning up the heat, I decided to recharge the system and started by replacing two of the three hoses as well as a new orifice tube. Now I'm not an AC guy, however our son does work in the commercial HVAC world with access to all of the proper tools. Neither of us are familiar with auto ac systems. He understands how they work but unfamiliar with how much refrigerant and oil should be used... We removed both of the old hoses (one on the high side and one on the low side) and covered the hose connection points with a clean rag then purged the system with nitrogen which produced a gurgling noise and sporadic spitting of oil into the rags. He then connected his vacuum pump and this ran for approximately two hours. Again this started with a mist of stinky oil from the vac exhaust which cleared within the first half hour. Then after running for the two hours and holding vacuum to confirm no leaks, he used the vacuum in the system to pull 19oz of r134. Then I started the engine and the compressor would cycle on and off. He added a 7 oz can of PAG oil and compressor continued cycling on and off. Next we added a 12oz can of r134 and compressor ran constant with low side gauge reading 30psi but air temp coming out of vents was 65 degrees. Tried adding another 12oz can of r134 however system would not take it. We're guessing we added too much oil or the compressor is shot? Need help please!
Not Cool!
- Thread starter catbird7
- Start date
Could be a few things. Which pag did you use? Some compressors are sensitive. Over charged, or maybe pulled vacuum at wrong point and pulled debris backwards? Maybe some mineral oil from the r12 system was pushed into compressor?
If upgraded to 134A it should only take 7oz to 10oz of 46, which is what the first few 134a systems used.
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If upgraded to 134A it should only take 7oz to 10oz of 46, which is what the first few 134a systems used.
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If on ports should be ok. How far are you from zip code 08873
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I'd get it evacuated with an automotive a.c. machine, put in less oil, try to recharge before you go replacing anything.
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junk
Full Access Member
What was the high side pressure running?
31oz of charge is low I believe. Now did the 7oz can of oil have any freon in it? I've read and been told you charge R134 to 80% (numbers vary) of what the R12 charge was supposed to be. On these trucks I think the R12 charge was 44oz but have seen higher depending on data source.
On my truck I charged it to 30oz of freon. It was cool, but not cold. I then added freon while checking temps. I did this as 2000 rpm. I had a vent thermometer in my dash and used an IR on the drier/accumulator under the hood. I charge it until those thermometers read the same. In my case I was able to hit 32 degrees.
If you high side pressure is under 175 or 150 I'd be suspect of the compressor. Also if your charging in the heat and humidity you probably need a big fan blowing through the front.
Good luck.
31oz of charge is low I believe. Now did the 7oz can of oil have any freon in it? I've read and been told you charge R134 to 80% (numbers vary) of what the R12 charge was supposed to be. On these trucks I think the R12 charge was 44oz but have seen higher depending on data source.
On my truck I charged it to 30oz of freon. It was cool, but not cold. I then added freon while checking temps. I did this as 2000 rpm. I had a vent thermometer in my dash and used an IR on the drier/accumulator under the hood. I charge it until those thermometers read the same. In my case I was able to hit 32 degrees.
If you high side pressure is under 175 or 150 I'd be suspect of the compressor. Also if your charging in the heat and humidity you probably need a big fan blowing through the front.
Good luck.
The oil was in a can similar to the r134 however it was just PAG oil no refrigerant. Did not take note of the high pressure reading from last night. We'll start this evening by reconnecting the gauges and I'll fire up the engine with ac on and verify high side is greater than 175 before proceeding. If so, we'll remove everything as Danielle suggested and start over without oil.
Definitely put oil in, just try closer to the 7 to 10 oz of spec, not 19 
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BDCarrillo
Full Access Member
+1 on the big fan blowing on it. You can also hose off the condenser. The low pressure sensor can also be jumpered to prevent it from short-cycling as you fill 'er up.
typ4
Full Access Member
Did you replace the drier? If not, that is a must, it holds some oil. I disconnect things, blow thru evap and condensor to push out oil, remove compressor and drain it, stand on end, ports down, rotate shaft, oil comes out. Reconnect everything add 4-6 oz oil to comp, rest in drier. 2.5 cans of 134a and it should work good.
needlenose
Full Access Member
I would do exactly as has been suggested. Especially starting over with a fresh drier and *no* oil in the system(meaning flush it). Then charge with oil. Put 1/3 in suction port of the compressor and rotate the compressor clockwise(from the front) after you hook up the lines. Put the rest of the oil in the drier. Vacuum, then charge with refrigerant. Preferably with scales if you can rent them. Make sure to purge your lines between cans. Add .5oz loss per can plus 1oz line loss per complete charge to your weight.(or something close to that)
Not trying to be an alarmist, but look the compressor over for oil leaking. I was misinformed on the oil charge one time and it started pushing oil out around some of the bolts(not on a Ford). I was 50% over. If the system was not flushed and you added 7oz, you may be considerably over. The condenser won't cool as well with a high oil charge and may be contributing to the poor performance.
I would strongly recommend that you flush out any old oil(better to just replace if you can). If the system sat unpressurized for any considerable length of time there is probably a lot of moisture bound to the oil. You really want that out.
Not trying to be an alarmist, but look the compressor over for oil leaking. I was misinformed on the oil charge one time and it started pushing oil out around some of the bolts(not on a Ford). I was 50% over. If the system was not flushed and you added 7oz, you may be considerably over. The condenser won't cool as well with a high oil charge and may be contributing to the poor performance.
I would strongly recommend that you flush out any old oil(better to just replace if you can). If the system sat unpressurized for any considerable length of time there is probably a lot of moisture bound to the oil. You really want that out.
Thanks to all for the helpful replies, unfortunately this is the height of AC service season and dad falls somewhere below the almighty dollar! Therefore my "AC guy" (son) worked late last evening and didn't fit me into his schedule....... Hopefully we'll have time this weekend to evac the system and start over better informed thanks to "you all" or as we say in central Appalachia "you-ins". Thanks Again!
Checked PAG oil can last evening and it's labeled "PAG 100".
Followed you-alls advice and everything worked out just fine. Seems to be working probably as good as can be expected with a 30 year old compressor. Not as cold as "new truck" however certainly better than opening the window. These were the gauge readings when complete.
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