I just completed converting my 1987 F150 A/C system to 134a. The system has been empty with a hole in the condensor for many years.
I replaced the O-rings, condensor, accumulator, and cutoff switch and flushed the system. I removed the compressor and drained as much of the old oil out. Following the advice of a few, I went with Ester oil with the UV dye instead of the PAG 46, with fear of any residual mineral oil.
With a clean system and new parts, I wasn't sure how much oil to put in. The parts guy at my local O'Reilly's pulled out his book and said that I would need to put 7oz of Ester poured directly into the suction side of the compressor. That amount seemed low to me but I went with adding the 7oz to the compressor.
After vacuuming and checking for leaks, I charged the system 80% with 134a. The pully on the compressor ran smooth and quiet but when the compressor clutch kicked in, the compressor became very noisy with a loud clattering sound. It sounds like an engine running without oil in it. The A/C works fine and gets cold, it just worries me that the compressor may not have enough oil in it or its on its way out. I checked the best I could for the source of the sound and it sounds like it may be the clutch but wanted to ask those who are more knowledgable than me if it could be that it needs more oil added.
Thanks,

 

If the compressor turns on and off, then theres not enough 134a in it, just add some more till its at the right psi (according to a gauge) for the current temperature of the day and it shouldn't click anymore. I just filled mine 2 weeks ago using the gauge on the can from wally world and its working great again.

 

Thanks for the reply tman. The compressor runs and the A/C blows cold, its just that when the compressor clicks on it makes that loud clattering sounds much like the sound valves make on an engine make when there is no oil. I'm trying to find out how much Ester oil needs to be added to the system after all the mineral oil was removed. I found a capacity chart that showed 10 - 11oz. I'm thinking the amount I was told was just for the compressor. I hope I didn't screw up because I installed a new condensor and a new accumulator and didn't add any oil to those. Do I need to start over and add oil to the condensor and accumulator to bring the total up to 10 to 11oz or can I just inject 3 to 4 more oz. into the system?

 

More then likely the oil is fine. The oil is used to help move the 134a around the A/C system, otherwise it would just sit in the system and not circulate through the orfice tube and turn from liquid to gas and cool the truck.

What is sounds like to me is your clutch is going bad or maybe just rusted up from sitting for so long. You can buy just the clutch and replace the old which is what I would do if it were me.

 

For each component replaced you are supposed to add a specified amount of oil. I added whatever the size of the small PAG oil can is, don't remember how much is in one can. If it's not the clutch making the noise then the compressor is going to die, they suck brand new.

 

7 oz of oil would probably be fine but it wouldn't hurt to add 3 or 4 ounces. The clattering is definitely your clutch if it doesn't do it when the clutch is engaged and your AC is supposed to cycle, not stay on constantly.

 

A/Cs do not cycle in Florida.

 

Thank you everyone for the information. I'm hoping it is the outer clutch plate that is rusty and causing the noise. I also noticed that the pressure on the high side was extremely low. The guage shows about 30 and the low preesure guage shows about 80 even though the ac is cold. I'm going to check if that may be from a bad valve stem on the high pressure port.

I'm wondering, if I add 3 to 4 more ounces of oil in the low side port wouldn't the required amount of oil settle in the condensor and accumulator anyway? It seems that if oil is circulating it would get into those components. Or is it necessary to recover the 134a I put in and start over with adding oil seperately to those components?

Sorry if these are dumb questions. This is my first conversion, so be gentle.

 

The oil will distribute itself. If the high is 30 and the low is 80 you've got problems.

 

Yeah the low isn't 80 even at rest, you've got something messed up or bad gauges. And yeah if it's hot/humid enough it won't cycle but generally it will.