30 on the low side
150-175 on the high side

 

It all depends on outside temps. Higher the outside temp the higher the correct pressure will be.

90 outside = 35 to 40 low side
190 to 225 high side
44 to 50 degrees from the vents


100 outside = 40 to 50 low side
200 to 250 high side
52 to 60 from the vents

 

my pressures are right where crow said the temps are higher by about five deg and the in and out of coil are within two deg i think the low pressure switch is givin me the intermitten fit but the air in the sd is no where near as good as it is in my obs

 

What year is the obs? Does it have r12 or 134? The 134 will never cool as well as r12. That may be the difference you are feeling. The sd I have now will only produce high 40's at the vent. My obs with r12 would put out high 30's low 40's Makes a big difference in comfort. The r12 will cool down much faster also. In my hotrods I always use freeze 12, it's a drop in replacement for r12. Works really well. Also all those myths about mixing? The oil is the difference, freeze 12 is a combination of 80% 134 and 20% r12. It uses the same oil as r12.

 

If its quitting from time to time and then going back to working check the clutch clearance on the compressor. Basically if you see a gap just big enough for a sheet of paper then its right, if it looks like a piece of card board or a screw driver tip would fit in the gap its to large.

Ive seen undercharging cause the systems to freeze up. Ive got a f150 that freeze solid aka you can see ice on the evap. Thought my powerstroke was doing the same thing and even said that in a post on here getting them confused. But what was actually happening on the powerstroke was the electro magnetic clutch was to weak when it got hot to pull the plate in and engage the clutch. So you had a/c when you started off but after driving for awhile it would start blowing hot air. I took a shim out of the clutch and it works great now.

So check the gap at the clutch on the front of the compressor. Its suposed to be .033 to .038 or something like that but mine was so bad you could drop one of those spark plug gap measuring disc into it

 

The highside needs to be outside temp x2 plus 10% and the lowside should be between 10-30psi.

 

my obs is 134a

 

I have been following this because my AC is not as cold as last summer. AC tools like high/low side gauges are some of the tools I don't have. My AC is running fine and gets cold, just not as cold. I was considering just adding some 134a like I have done on previous vehicles. But I wanted some opinions or possibly a shove in the direction of a write up.

Any info is appreciated and thanks for the help,
Pat

 

with a temp probe if you measure the temps from both lines coming out of the coil box they should be within 2deg of each other if thats the case its suppposed to have the proper charge or close to it. you need a contact probe for temp ir temp gun wont give you an accurate reading on shiney piping