I put a dial pressure gauge on the Low side only of my A/c system and it's reading middle of the blue. If I reve the engine up off idle the pressure drops down to green. I'm debating charging it up a bit. I put a temp gauge in the air vents in the center of the dash, in the sun this morning, it was blowing 51*F @ idle. What do you guys think? FYI, i had no low pressure side cap, so I had to clean the shrader valve port with compressed air to get years of grit and crap out of it. so i'm picking up a set of caps today at work.

What's the high side pressure look like?

NO IDEA. I don't have a manifold gauge. just a decent low side dial gauge.

You could try topping it off, but it's kinda risky without knowing the pressure on the high side.

Is 51 degrees the coldest it got?, it should get colder than that. R12 (if it is) should get down to about 38 at the vent, if it working correctly What do you see when you look at the site glass?

yeah, 51F is as cold as it got. it's R-134, came from the factory 134. I got a 94... so must of been one of the first years. When I look at the sight glass I see a little bubble.

51 doesn't sound too bad at idle depending on the ambient temps. What is the outlet temp when you're driving at freeway speed? I wouldn't recommend trying to add freon in a r134 system without being able to monitor both low/high pressure.

You should see a multitude of tiny bubbles passing through the site glass, basically pin size bubbles. With it dropping when rpms are increased, you probably need to add some R134 if you have the equipment to do it. You might also have an A/C shop exchange out the R134 for some new.

changing out the Freon? I never heard of that. Is that like changing your tire air for summer/winter air? lol. Either way... I think I'm gonna buy my own Manifold A/C gauges to see the pressure on the hi/low sides. A/C has always intimidated me... and i never used it much either. but lately i've been very interested in learning to work with a/c's and using it makes driving a heck of a lot better in FLorida in the summer time. <img src="/forums/images/graemlins/cheers.gif" alt="" />

2 other things:
1- my drier looks Original. the guy before me said the a/c was worked on, but in miami i doubt they do things "right". so it's probly has a 11yr old drier on it. should I put a new one on it?

2-What about oils? I don't know which oil is used where and/or why.

3- Flushing? My truck came orignally 134a, so it never had r12 in it. but does flushing an 11yr old system help?

I just found this site recently, but if you have an AC question, it looks like the place to go:
http://www.ackits.com/