Hey guys, new to this forum. Just switched my ac system from r12 to r134. Wondering how many ounces of r134 to use to fill a completely empty system. Thanks

 

welcome to FTE.
there should be a tag on the radiator support or hood with ac capacity.
134A charge will be 80% of R-12, or around 3 lbs.

 

Once you've done the swap, buy a low-pressure charge system with a pressure meter and charge from there. I believe at 80 degrees it should be at 35 p.s.i. running.

 

Ok, so i charged it to 35psi at idle. The thing is when i throttle up the engine it drops to 20psi and the clutch disengages. Does that mean i just gotta add more? I have about 27 ounces in it so far

 

27 ounces is not even 2 lbs. you should have closer to 36-38 ounces in the system.
you also want around 35 psi on the low side and no more than around 250 psi on the high side.

 

Ok, ill put more in. Thanks man

 

Mine did the same thing. When they're undercharged the compressor engages and disengages more rapidly because of the lower contents of the system. Once the systems full it should stop doing that.

 

Hence the reason why you should charge by volume not pressure.

 

So how many psi do i need to stop that at idle. 30 to 40 psi is the safe zone on the low side. Its holding at 35 at idle right now

 

rla2005 is correct, it's volume, not pressure that will stop the idle dysfunction.
I charge by pressure, because once the pressure remains even at 35 it's typically full. Also, you need to check the outside temperature. 35 PSI is only accurate if it's roughly 85 degrees. The filler hose you get should give you pressures v. temps.
Sorry for the confusion.

 

trying to find the oz for my 1998 E150 with the 5.4 only AC in front..you have any idea..no sticker on hood or engine bay!
TIA

 

Just google any truck or car anytime the sticker is missing
Rule of thumb is the new systems use way less than the old ones
I can say without even looking that your 1998 truck takes just under 2 pounds
Whatever it takes, you add 4 ounces for the gauge set
I will look now on google for yours frodo2222
Found one 4 Seasons puts out charts as do others
Yours holds 44 ounces R134a and 9 ounces PAG-46 oil (without rear air) 64 and 13 with

 

thank you!!!..mine was working great BUT in the process of building out the rear of van punctured a line back there and although there was no AC working in back the line did hold pressure so I ended up taking out all the lines and assorted parts of back AC..a tiny amount of yellow oil came out of back line but all the front didnt get touched other than to put a cutoff block off kit I'm assuming since it had the pag oil in the compressor etc etc in front it should be ok but your thoughts?

 

You might need to split the difference depending where the block off plugs are located
Meaning it might take more freon than a simple front only unit
With a difference of 20 oz. you might need 10 more if the evap only is blocked off
If the block offs are up front, you may only need a few more ounces

 

This is the ‘87-96 F -series forum so you should be asking in the E-series van forum.

Do you have a conversion van? The van has rear a/c that isn’t working or it only has front a/c but there are lines for rear air? There would be a difference in amount of charge. You are going to replace the lines with front a/c parts?