Factory A/c question pag oil capacity

[C_Forte_75]

A/C specification question?

Does anyone have the spec on how much page oil to run on a stock 1979 Bronco 351m with factory ac? Everything has been completely replaced so no estor oil for me. Thanks

 

[DirtDonk]

Only a few with the '78 and '79 Broncos around here (as popular as they are among us!) but I might have some info if I can dig it up.
My '79 F350 has a decal for the amount of R12, but not sure it lists the oil. If we find the amount of refrigerant though, can't we extrapolate the amount of oil from that? I was thinking there was a consistent ratio depending on the type of system.

I also think that there were at least two different sizes of A/C system. I seem to remember seeing different decals on different trucks. With mine having the larger for some reason. Seems the Bronco with it's larger cab would have had the big system too.

Let you know what I find shortly.

Paul

 

[C_Forte_75]

Thank you Paul! I am not aware of a ratio and I will be running 134 instead of r12

 

[DirtDonk]

Here's all I've got until I can find something in the book.



Do you already have that decal?

Paul

 

[DirtDonk]

Sorry, don't have that info here.

Good luck. Surely someone here will be familiar with the different setups and know approx. how much to use.

Paul

 

[bronconut73]

Chilton manual should be able to tell you how much R12 would go in it and then you put in 80% of that number in R134

 

[Broncobowsher]

I had to do this with my '77 with a 460. It isn't so much an amount but a level. The manuals show how to make a dipstick that you stick in the filler hole and use that to check the level. Was a bit obscure of a reference.

As for the Freon amount I fill by superheat. You have to monitor the suction temperature and watch the gauges. quit adding when you are about 5° above the temp on the gauges. That is if the gauges say 40°, the actual suction line temp is 45°. The tricky part is getting an accurate temp of what the inside of the line is without getting the heat from outside. Get any engine room heat and you can overcharge.

In my case it was exactly 2 cans.

 

[Skytrooper15]

According to my Dupont info you drain the compressor oil out and measure the weight and put in exactly the same amount of pag oil back in the compressor.Easiest way to do this is remove the compressor and drain the oil out the suction line port.Now it is important to get all of the mineral oil out or you will have stopped up strainers/metering device.You have to replace the metering device to the correct refrigerant anyway.According to the decal of my 1978 F-100 it calls for 4 ounces of mineral so if you can't measure what is in your A/C or you lost lots of oil removing the R-12 or it leaked out go by 4 ounces.Flush the compressor out with alcohol that you buy by the gallon at hardware stores and also the lines and condenser,evaporator and be sure to replace the accumulator/drier when you have it clean and clear of mineral oil.Some oil always travels with refrigerant but mineral oil will not be picked up by R-134A like R-12 so getting all of the mineral oil out of the system is very important.Also while you have the lines off replace the O-rings with the green O-rings because they will work with R-134A and the black one leak.Good idea to replace O-rings every time you open a fitting.On a 90 degree day my chart shows about 40 degrees for R-134A.If you let the suction pressure fall below 32 degrees ice will blow out of the registers in the cab which sounds good but will also cause the evaporator to ice up.Hope this helps

 

[Broncobowsher]

I would skip the alcohol flush, more likely to do more harm than good. Mineral oil residue is fine in an R134a system. It's been known to help seal old rubber where new rubber that has not been exposed to years of mineral oil will leak.

I just pulled the compressor, drained it out the fill/check hole, put some of an old bottle of PAG in, rolled it around, spin the crank, and poured that out. Then filled with fresh PAG. Vacuum and fill. Any O-ring I opened I put in the new green O-rings.

 

[Skytrooper15]

Don't like to bring up yesterdays post but any amount of mineral oil will cause sludge and acids to build up causing you to have to replace the restrictor several times.Dupont that invented R-134A refrigerant recommends three oil changes to get All of the mineral oil out of an a/c system.Also you have to replace the restrictor oriface with one that is made specifically for R-134A.Also mandatory is a suction accumulator/drier change because lots of oil will accumulate inside it and it's just easier to replace it than it is to try to clean out all of the residue inside.The alcohol flush is recommended by refrigerant and lubricant makers.Pag is made out of diethylene glycol which is the base material for antifreeze and turns mineral into an acid.One word of caution with a change to R-134A refrigerant is you only get 80% capacity of cooling than you do with R-12

 

[Steve83]

Read the first post - he has NO oil in the system. Probably only shipping oil in the compressor, which SHOULD be flushed out with the correct commercially-available flush solution. Rotate the compressor BY HAND ONLY as the flush goes through, and for at least 10 full revs after the last liquid passes through (when it's REALLY hard to turn).

The TSBs linked in this caption describe the oil capacity for R12 to R134a conversions - it's 4oz. MORE than the mineral oil capacity (according to the last TSB that addressed it directly). The oil capacity is NOT directly related to the refrigerant capacity. Ford is the only brand that uses PAG-46.


(phone app link)

 

[Skytrooper15]

Read the first post - he has NO oil in the system. Probably only shipping oil in the compressor, which SHOULD be flushed out with the correct commercially-available flush solution. Rotate the compressor BY HAND ONLY as the flush goes through, and for at least 10 full revs after the last liquid passes through (when it's REALLY hard to turn).

The TSBs linked in this caption describe the oil capacity for R12 to R134a conversions - it's 4oz. MORE than the mineral oil capacity (according to the last TSB that addressed it directly). The oil capacity is NOT directly related to the refrigerant capacity. Ford is the only brand that uses PAG-46.


(phone app link)

If everything has been replaced all of the hoses,evaporator,condenser,metering device,suction line accumulator/drier and he has a Ford specific compressor designed for R-134A the compressor should have the correct charge of pag oil in it and it will have a tag on it saying so or it has a tag that tells you how much of what type oil to use but to be on the safe side a system flush with alcohol won't hurt,just disconnect the lines at the compressor and flush.Or he can wait until the full moon on a Sunday night and without any kind of light while parked in a graveyard just get a voodu woman from New Orleans to sacrifice three live chickens for luck and then just charge it up with propane and hope for the best..