Any a/c guys out there?

[vr2jetta]

I have a 1990 325i and I am trying to get the a/c working. I have changed the expansion valve, the drier and the o-rings to the compressor. I brought it to a shop today to have the system vacuumed down and when I got it home I filled it with refridgerant (134-a). It is circulating through the system, I can see the dye flowing through the glass in the drier, but is not blowing that cold. Is there anything else I should be looking for? I charged it to about 55 psi on the cold side and tomorrow I will re-connect my gauge to see if it has gone up, thinking I possibly over-filled it. I was steadily checking it as I filled it and never seemed to get cold, just cool. Any ideas?

[bmw325_num99]

Did you confirm that the system still had a good vacuum before you filled it up with refrigerant in the morning? If there was a leak then the vacuum wouldnt have lasted long but could have allowed enough refrigerant in to show dye.

[bmw325_num99]

....At the shop I used to work at, we would leave the cars overnight with the vacuum gauges attached to confirm they were leak free in the morning.

[vr2jetta]

Did you confirm that the system still had a good vacuum before you filled it up with refrigerant in the morning? If there was a leak then the vacuum wouldnt have lasted long but could have allowed enough refrigerant in to show dye.

No, I brought it straight from the shop and filled it up. They connected the machine and left it on for about 30 minutes and gave it back to me. I had previously filled it with 134 and dye and checked it for leaks at nightfall. It was leaking from the o-rings in the compressor so I changed them, the expansion valve and drier while it was empty, to ensure it would work properly, and now it still sucks.

[Dominic49]

i dont know how many psi i have mine charged to but i did 2oz of pag and 2.5lbs of refrigerent blows at 40 degrees

[bmw325_num99]

And now you have gone through the car again with its pressurized system and you have not seen any dye leaking out? Did you confirm the 55psi today? Has it dropped or risen since the first post?

[vr2jetta]

I woke up late this morning and the wife left for work before I had time to check it. I charged it to 55 psi, but when I put the gauges on it 1-2 hours later before the wife left for work yesterday I 'think' it may have gone up to 60 or so. Could it have gone up after charging due to refriderant expanding or something? I will def check it tonight or the tomorrow. I have to change some relays and the guibo so I will have it all day.

[vr2jetta]

i dont know how many psi i have mine charged to but i did 2oz of pag and 2.5lbs of refrigerent blows at 40 degrees

Whats the outside temp when you are blowing 40 degrees out the vents?

I just went outside and checked it, it was at 45 psi. It is 85 degrees outside so the gauge says it should be about 50-55 psi. I added more refrigerant and it fluctuated between 45 and 50 but never really went up. I 'think' I put about 6+- additional ounces in it. I put a thermostat in the vent and it is reading 50 degrees. If I remember correctly the a/c can only drop temps by 30-35 degrees, so this should be accurate, but........on re-circulate it should get cooler. If it stays where it is I think I will be OK, But damn you Dominic for telling me 40! LOL!

[30secE30]

did you feel the lines?
the discharge line (hot side)coming out the compressor should feel very hott
the liquid line (hott Side) coming out the condensor should feel hott but not as hot of the discharge line
the liquid line on the (cold side) after the metering device should feel very cold
the suction line (cold side) back to the compressor should feel cold

do you have the psi on hott side??

[vr2jetta]

did you feel the lines?
the discharge line (hot side)coming out the compressor should feel very hott
the liquid line (hott Side) coming out the condensor should feel hott but not as hot of the discharge line
the liquid line on the (cold side) after the metering device should feel very cold
the suction line (cold side) back to the compressor should feel cold

do you have the psi on hott side??

I only have the cheap gauge that tells me cold side psi, but the line where the refridgerant goes in is cold. The hot line running into the cabin is warm, but not real hot.

[30secE30]

hmm that should be normal then. if you had the exact low pressure and the high pressure readings i can help you out. when you saw the needle fluctuating was it really fast??

[vr2jetta]

hmm that should be normal then. if you had the exact low pressure and the high pressure readings i can help you out. when you saw the needle fluctuating was it really fast??

No, it kinda slowly went up and down like the freon was equaling out after I put it in. I have it all ripped apart now, in the process of changing the guibo a CSB so it will all be put back together tomorrow and I can troubleshoot it further then.

[noke325]

This is my first post on this board but I'd like to interject and educate a little. I am an auto technician by trade and have been making my living doing so for 15 years. I have worked on many a/c systems and I have some info for you.

The principles of air conditioning are physics, pure and simple, and are universal for your car, your home HVAC, your refrigerator. All its doing is raising and lowering the refrigerant pressure in a controlled manner.

First off, when you retrofit a car from r-12 to r-134a the size of the charge needs to be 85% of the r-12 charge. So if your system originaly held 2.5lbs of r-12, charge 2.125lbs of r-134.

If you've charged 2.5lbs r-134a on a 2.5lb r-12 system, thats too much. 55 psi working low side pressure is not low enough to give you cold duct temps, especially in FL. Overcharging will give you high, low-side temps/pressures. Which also gives high, high-side temps/pressures.

Youre pressures are indicative of what your temps will be. I dont remember the exact values but, 55psi will be roughly 55 deg evaporator core temp. You need to be in the area of 30-40 to get the car to cool down.

Now, your rest (not running) pressures on both sides needs to be close to the ambient air temp. If its 85 deg outside, the rest pressure needs to be probably within 10 psi of this. Remember, underhood will be hotter so look for something north of the ambient air temp. On an 85 deg day I look for something around 95 on a r-134 system.

You really need a set of gauges to monitor both sides. Because if your high side is high then your low side will probably be high - indicating a possible overcharge or if your high side is low and the low side is high it could be a bad txv (thermal expansion valve). Since you've replaced it, lets look at something else. Is your condenser fan running once you push the a/c button? This is important as your condenser is on the high side and needs to stay under 300 psi. I really like to see the high side below 250. This goes back to the pressures on both sides and being able to monitor them. Your expansion valve can only reduce the pressure so much then the pressure rise increases at a linear rate. Thats why, on super hot days, the duct temp doesnt seem to get cold enough. Because even the rest pressure is higher that nominal which causes the high and low side to be higer than nominal.

Now, while the system is running with the proper amount of charge, the sight glass in the drier should be clear or with few bubbles. Cloudy or alot of bubbles indicates the wrong charge.

If the guage you have came with the refrigerant, and you got it as a kit, I would toss it. I have used those before and dont trust them AT ALL!

If you can get rest pressures and working pressures from both the high and low side that would be VERY helpful.

Alot of what these other guys are telling you is not bad info. Especialy feeling the lines. High side (small diameter pipe/hose) should be hot to the touch. Low side (large diameter) should be cold. As a matter of fact, the low side should sweat alot in the Florida humidity if its low enough.

When you get it right, you should be able to see duct temps around 40-45 degrees on a 90 degree day. An efficient a/c system should drop 45-50 degrees from ambient with the windows up, the blower on high and in recirculate mode.

Hope some of this helps.

[Jean]

noke325 - very good info, thank you!

[thereisnoyun]

noke325 - very good info, thank you!

hell yea! new A/C guru, we need a A/C subforum.