'98 Cutter Dash Air Charge

[Koheleth]

Working on dash air on '98 Cutter, 35 foot, Cat engine. Replacing compressor, expansion valve, dryer. Need to know the proper R-134 freon charge amount and proper oil type and charge amount. Does anybody know what they are?
thanks, Neal

[bobmiller1]

i did the same work on my 01 390XL 2 years ago. I also had a bad electric fan motor under the front end in front of the condenser, does your new dryer have a sight glass on it ? if so, when the compressor is engaged keep adding freon until there is no bubbles present in the sight glass. R-134 charge amount is way more critical than R-12. A 1/4 lb. over charge will actually make the system blow warm. If you have no sight glass then after you pull a vacuum I would add approx. 1 oz. oil for every component you have changed with no more than 4 oz. in total. Then I would start with a 1 1/2 lb. charge to start with and monitor duct discharge temp. keep adding freon until duct discharge temp. drops to the lowest point, when temperature starts to rise that's it. remove a small amount to get the temperature back down again. Make sure the electric fan is running at the condenser if you have one up front. Generally high side pressure should not exceed 200 PSI. and low side pressure will be around duct discharge temperature.

[Koheleth]

Thanks for the information. The new dryer has a sight glass, as did the old one, and there is an electric fan in front of the condenser under the front. Looks like a hot rod radiator fan. Haven't checked it yet, but will. Thanks again.