Refrigerant charge amount, engine air

[atsrmf]

I have a 1987 Gulfstream Class A with a 1986 Ford 460 driveline. I want to connect a recycler and evacuate the system, vacuum, and then recharge with R-12.
My question is, how do I find out the recharge weight in pounds? There is no sticker on the engine, and I know better than to call the factory for an answer. If I can't find out, I can always charge until the pressures are within specs for the ambient temperature, which would probably be close enough.
The chassis is John Deere and I think the driveline is considered an F-350.

[Matt_Colie]

atsrmf wrote:
I have heard of this product and seen it in parts stores, but have never talked with anyone who has used it. For a big solar oven such as a Class A motorhome, this might be the stuff to use. The fire hazard is the ONLY setback.

I think one of the BIG Pluses is that you don't have to change the oil or replace all the seals to change from R-12. I do think it is illegal in California (one of the few good things that is), but I don't know that for a fact.
The fire hazard is only slightly higher than 134, but at least the fumes are not toxic.

Matt

[Rick_Jay]

If your system is functional now, but not cooling fully, I would follow what dougrainer calls the "saturation method" and just slowly and carefully add more R-12 per his method and what I mentioned earlier in the thread.

IF you ever need to open the system again, then you can replace the drier with one with a sight glass, but I wouldn't open up a functioning non-leaking system just to install one.

If you have 15 lbs. of R-12, that should be enough to completely recharge that system 3 or 4 times at least.

As an aid to get the R-12 gas to flow into the system, put the R-12 bottle in hot water for a while before hand and while charging. Or leave it out in the sun. This will build up the vapor pressure inside the bottle.

You mentioned adding an electric fan. Not sure how it was done on that era vehicle, but I believe it's common for a vehicle to have an auxiliary electric fan that comes on with the A/C in addition to the normal cooling fan. This is to keep sufficient fresh (cool) air flowing through the condenser when the A/C is engaged.

For what it's worth, when I do this type of work, I make sure the refrigerant bottle and what I'm doing IS NOT in plain view of the neighbors and/or from the street. No sense in getting folks curious about what I'm doing. 😉

Good Luck,

~Rick

[dougrainer]

Usually when you change refrigerant composition(12 to 134a) there is not the same exact ozs used. But it is close. Ford Motorhome chassis built for 134a use 2.25 to 2.75 lbs of 134a. Using a dial a charge is best but it will be difficult to find the lbs used on your system. I use the saturation method all the time on older vehicles where I cannot find the specific charge. It just takes time because you have to slowly charge. Doug

[atsrmf]

Matt_Colie wrote:
Atsrmf,

I don't know where Indio is, but if it is not in California, look up a refrigerant called HC-12a. It is a hydrocarbon based that is completely compatible with all things R-12. It is almost three times better then R-134a at heat pumping and is completely non-ozone depleting.

But, (like HC-134a) it is flammable. There is an advantage there in that if R-134a burns, the by-product is extremely toxic.

HC-12a is a combination of pure (not cooking grade) propane and iso-butane (iso in this case means the molecule is a different arrangement) I have used this to great success.

If you are afraid to have several pounds of flammable material there, then think about the amount you already have in the LP tank and fuel tanks.

Matt

I have heard of this product and seen it in parts stores, but have never talked with anyone who has used it. For a big solar oven such as a Class A motorhome, this might be the stuff to use. The fire hazard is the ONLY setback.

[enblethen]

Itis hard to say how much it would take of whatever refrigerant is used. most listing are for Ford produced vehicles and not MHs chassis.

[atsrmf]

I appreciate all of the replies so far. I should have converted the system to 134a from the beginning, but didn't. I also failed to put in a drier with a sight glass, but have found in-line versions that can be added.
I bought an R-12 recycler 2years ago and have about 15 pounds of R-12 in a canister. I plan to evacuate the system and install the sight glass and replace an o-ring. No Freon will be lost into the air this way.
When I do repair work on automotive A/C systems I like to know the recommended factory specification for the amount needed, and re-charge that way using a refrigerant scale. I wondered if anyone knew the amount with this particular motorhome.
Currently the A/C doesn't put out very cold air, so I want to start over. The condenser is new, along with the compressor and drier. I also added an electric fan that has a switch on the dash.

[dougrainer]

Matt_Colie wrote:
Atsrmf,

I don't know where Indio is, but if it is not in California, look up a refrigerant called HC-12a. It is a hydrocarbon based that is completely compatible with all things R-12. It is almost three times better then R-134a at heat pumping and is completely non-ozone depleting.

But, (like HC-134a) it is flammable. There is an advantage there in that if R-134a burns, the by-product is extremely toxic.

HC-12a is a combination of pure (not cooking grade) propane and iso-butane (iso in this case means the molecule is a different arrangement) I have used this to great success.

If you are afraid to have several pounds of flammable material there, then think about the amount you already have in the LP tank and fuel tanks.

Matt

Indio is in the area of Palm Springs California.
In this case, if you can find Freon 12, you can actually use the sight glass in the dryer to charge the system. You just charge until the bubbles are gone. Another way to charge any Dash AC system if to have a digital thermometer inserted at the closest Dash vent to the Evaporator and slowly charge until you flatten out on the downward cooling. Once it plateaus at say 55 degrees and then starts to climb up you have reached saturation point and stop the charge. Doug

[Matt_Colie]

Atsrmf,

I don't know where Indio is, but if it is not in California, look up a refrigerant called HC-12a. It is a hydrocarbon based that is completely compatible with all things R-12. It is almost three times better then R-134a at heat pumping and is completely non-ozone depleting.

But, (like HC-134a) it is flammable. There is an advantage there in that if R-134a burns, the by-product is extremely toxic.

HC-12a is a combination of pure (not cooking grade) propane and iso-butane (iso in this case means the molecule is a different arrangement) I have used this to great success.

If you are afraid to have several pounds of flammable material there, then think about the amount you already have in the LP tank and fuel tanks.

Matt

[Rick_Jay]

atsrmf,

Does the system need repair? Is there any R-12 in it now?

If it's still functional and doesn't require any attention, you can just add more R-12. Of course, FINDING someone who can do that might be a bit of a challenge.

Again, assuming the system is intact, do you know if you have a sight-glass in the system? If so, you can watch it and slowly charge the system until the bubbles disappear. If yours doesn't have a sight glass, then a proper set of gauges and the proper charts for that engine should get you close enough. If you're not sure of the graphs to use, then add the R-12 slowly and monitor the temperature of the cold air coming out of the (usually) center vent when it's set to MAX (usually). Charge a bit, stop...check the temp...wait a few minutes...charge a bit more...check the temp. If it went down, repeat the process. If it went up, then stop charging. Putting too much in will reduce cooling ability. BE SURE TO USE A THERMOMETER DESIGNED FOR A/C WORK!!!

On the other hand, if the system needs to be repaired, it's been opened or leaking, then a conversion to R-134 is probably in order.

Good Luck,

~Rick

[enblethen]

You are going to have a problem finding someone to refill with R-12.
You should be using r134a.

[MountainAir05]

maybe around 4 lbs. will have to pull out the books to be sure. This is a good number since you stated a Ford 460. But as Doug stated one you get the stuff change and a good vacuum and put in 3 lbs and watch the bubbles and meter and go from there.