MikeyB

Spooler, are those numbers correct for R134? The numbers you posted appears to be for a R12 system. But it's been awhile for me also.

MikeyB

SSminnow

I do know that R134 systems run at higher pressures (both low and high side)(slightly) over the old R12 systems do.

Spooler

Those are for R134A systems. R12 numbers are higher. R12 low side =28 to 34 PSI, High side 250 to 300 PSI. It also depends on the system but the numbers will be close. As always the best way to deal with an A/C system is to measure the amount of freon in the system. Hince, Evacuate, vac, reoil(replace oil that was removed), and recharge with the proper measured weight of refrigerant. R12 systems that were converted to R134 are calculated as such. R12 weight x .8= Weight of R134A to use. R134a should be less than the R12 weight.

Spooler

R134A runs on less pressure than an R12 system. It takes less gas if you use R134a then R12. Volume of gas is less that is why the pressures are lower.

MikeyB

Are you sure? R134 should be higher since it has a lower density atom wise than R12. So R134 needs be run at a higher pressure to have the same cooling effect as R12.

MikeyB

Spooler

I am perty sure. Been about six years. Did alot of conversions from R12 to R134A. Never seen a R134A system perform as good as a Good R12 system. They are getting better these days though.

Berak

This is a common problem on the third gens. It's usually the fin temp sensor. If your R-134A is low, you probably should find out how it got low before you dump more in. Unless it was low from the factory, you got a leak.

Spooler

Not being poot head but if I were you I would put it on a R134a machine, Recover the refrig.( write down the weight), Vac it, measure the oil removed, replace the oil, then recharge it to the recommended weight. Take the after weight and subract the recovered weight. This will show if you were low or overcharged. Check the pressures. Pressures will change due to ambient air temp. Higher if hotter, lower if cooler. You don't have to take my word on it. If you have a leak look for the wet oil spot first. This is the fastest way to find a leak weather it be a line, condensor, or compressor(bottom between clutch and compressor). This dosen't work to good for evap. because you can't see it until it is removed. Then you will see it. Cracked lines are also hard to find(normally not much for the oil to hang on too. Have to look them over good.

bigdav160

Because pressure = temperature.

Look closely at your gauges. There is normally a temperature scale next to the pressure scale.

Now that rule doesn't work too well if there is something (air?) else in the system.

SSminnow

Oh I know there is a leak SOMEWHERE, but at this point, I am going to add the freon, and see how long it lasts. If it lasts me a year or so, then I will just add when it is low. If next month I have to add again, then I will find the leak and fix it.....

SSminnow

OK guys new numbers for you. Will not be able to tell you if the system still freezes over, as I am confined to the house the rest of the day today Tomorrow, will be back to drving around for work. Anyways here goes:


System calls for 1 LB 14 OZ

I added a 12oz can of freon, and @ 1/2 to a little less then half of another 12 oz can, so we will call it 14-18 oz of Freon to a system that calls for 30 oz. I also added the 2 oz can of oil. My readings are now:

@ idle 40 LBS low side and @ 265 on the high side

@ 1000-1200 RPM 32 LBS low side and @ 275 on the high side.

With the system shut off, and equalized, both low and high are reading @ 97LBS

It is @ 91* outside right now.

Hounddog

What about cooling out of pass side vents,did you monitor or feel a differance?

TheFog

Best way to charge an automotive system with an orifice type system is to charge by weight. Just recover (or vent) the r-134a and charge the system by weight. It’s the most accurate way. Also if you find yourself having to recharge often due to a leak that you don't want to fix, ADD OIL EVERY COUPLE OF CHARGES or your compressor will start doing a spot on impersonation of the Cummins clatter . Also if you do have a leak the UV dye will help you find it VERY quick, just add some and run it for a week and one night break out the UV light and you will be amazed at how it stands out where its leaking.

On the lower temps R-134 pressures are lower than R-12, but once you get above 60deg then it switchs and R-134a is higher pressure than R-12.
http://www.chillers.com/PT%20charts%...frigerants.htm



And yes venting r-134a is pefectly legal, R-134a is the propellant used in those cans of "canned air" to spray dust off your computer and stuff. http://www.fluoridealert.org/pestici...roeth-page.htm

Lloyd Henry

Good Morning
This may sound stupid but here goes anyway.I was on another site about a month ago and there was a person complaining of the same problem. AC freezing up on the highway but not in town ect. He went on to say that he thought it was the drain tube coming out of the firewall. He thought that because it came straight out that at highway speeds the air turbulence in the engine bay may be hindering the flow of the water ( you know the water that drains out every time you stop) out of the drain. He put a small preformed 90 degree hose on the vent tube and said he has not had the problem of freeze up since. It made sense to me so I put on on mine and have had no problems so far but I live in North Dakota and don't have a chance to use the air that often.
Sorry for being long winded but I hope this will help or at the very least it is a cheap enough to try.












c

SSminnow

NO not yet, but today will be the day. I do know that BEFORE I added Freon, the air coming out of the passsenger side vents was WEAKER, but not necesserally warmer/cooler. However, when my Dad rode in my truck a few weeks back, he asked if my AC was working OK. BUT, my wife rode inthe truck the other day, and had me turn the AC down, AND the vents away from her becasue she said it was too cold. So, I ask.....what would cause it to be warmer/cooler on the poassenger side as opposed to the drivers side vents????