how much freon?
 

I`ve searched and searched for this info on this website and could not come up with the #`s, I need. So here goes, how many ounces does a 1989 F-250
Diesel (if that makes any difference ) a/c system use(freon). Thanks

what are you going to fill it with r12 or r134a or something else.

My A/C book shows 3.25 pounds for a gas or diesel and 7oz of oil for gas, 10oz of oil for diesel. If you use 134a you should use only 80% or 2.6 pounds.

how much freon
 

Thank you for your quick response. Yes I`m changing it over to 134. I`m going to roll the dice and go with the $35 changeover kit. I have friends that have used this kit with success on other vehicles. I`ve already put in 36 ounces and needed to know the #`s that you gave me. It`s working fine but could be a little cooler. I`m going to put in 6 more ounces to see if that cools it a little more. Again, thank you.
Peter

One thing you can also check is the fresh air door to make sure its closed all the way. There is a vacuum chamber right above the blower motor, I used a zip-tie to make sure it stays all the way closed and run my A/C on max and it gets COLD!

did you pull a vacuum first? never overfill it more is not btter you only want low side of 35 to 40 psi

I think the 80% rule is a general rule of thumb and have found that on occassion 80% will cause the system to be overfilled and cooling to be inadequate. I have found the best way to charge with R-134 is to connect a set of gauges to both the high and low side of the AC system, pull a vacuum for at least a half-hour, start the engine and set the idle speed at 1200 rpm and place a fan on high blowing into the front of the condensor. Also, have a connected garden hose with a sprayer available. Place a thermometer in the center discharge vent inside the vehicle. With all windows closed place the AC on max or recirculate and the blower on high. Begin to charge the AC with R-134 and make note of the center discharge temperatures. Periodically spray the condensor to lower head pressure and to mix the R-134. Continue to charge until the center discharge temperature begins to rise. Stop. Remove just enough R-134 to get back to the lowest temperature recorded.

John

According to interdynamics it is 85%. Roughly 3 cans. Remember if you put to much it will blow hot air! Just my 2 cents.