TA_Freak

I don't claim to be an expert on AC, although I do have everything to do my own work - and I do. I just finished evacuating and recharging the AC in the TA. As we all know, the compressor calls for 1.5 Lbs of r134a refrigerant. So after the system ingests the 2 - 12oz cans, pressures are too low and it blows warm, with compressor clutch activated. I wound up adding a total of 3 Lbs and now my pressures are 40/240 low/high. I'm also getting 40º out of my vent and I'm happy. Has anyone recharged their system with only 1.5 Lbs?

B52bombardier1

I'd say you are probably over-serviced on 134A and I can't completely explain why it didn't cool at the lower level of refrigerant but does now. Though, I'd probably have misted my condenser with spray water to see if that lowered my vent temperature before adding a bunch more 134A.

Rick

jetech

3lbs. (48oz.) of 134a in a system that is supposed to operate on 24oz.? Wow. Here is some real good info on auto ac. There is a chart to check the system static pressure. It can indicate if the system is under or over charged. Click here

TA_Freak

Interesting. This morning my static pressure was 70 psi at 66 °, That's only 4.5 psi high.
At 300,000 - ish, I replaced the compressor, receiver/dryer and orifice tube. I flushed the lines as well. I seem to recall that it took a similar amount of refrigerant as well.
I've never replaced the condenser. The running pressures don't scare me and I'm cold in front of the vents. ???

jasons69chevelle

Charge it to what your tag says for the complete charge. AC should be cycling on low pressure switch every couple minutes at idle once it’s good and cold.

jetech

134a temperature /pressure relationship is not linear. At operating temps I think the pressure would be around 10-12 psi above normal. Not dramatic. Is there good airflow across the condenser? Might it need a cleaning? If it is slightly overcharged, it will most likely cool better if the charge was reduced a little. Otherwise enjoy being cool.

TA_Freak

It was short lived. The last two days, in the afternoon when it's warm - the cruise kicks off and then within a few miles the AC compressor clutch turns off. So I figured it had something to do with the 12v feeding or leaving the fuse since they both are fed off of the same fuse. No. The issue with the AC appears to be pressure. I had my tech2 with me and I commanded the clutch on and it would stay on until I got a message of pressure. The high side was at around 240 psi and low was 45 psi and the voltage on the sensor went from 2.3v to 2.78v when it shutdown and I got the message. Any ideas? Maybe I need to take it down again and only put in the 1.5 pounds and go from there. The pressures equalize when it's off so I don't think there's any blockage ... but what do I know. Any help would be appreciated. I'm hating the TA today.

jetech

Bad Pressure switch

TA_Freak

Really? I just replaced it several weeks ago.

B52bombardier1

As mentioned in post #2 above, lightly mist your AC condenser with your system running and the high side gauge hooked up. With the mist water, the high side gauge pressure should drop, your system should cool better and NOT SHUTDOWN. This will tell you that either:

1 - you are under-fanned at the condenser.

2 - you have a dirty, dead insect clogged condenser that does not allow cooling air to pass through the fins. For cool air to be available in the passenger compartment, heat must be shed from the condenser. Hot R134A won't produce cool air at the evaporator unless it loses its heat at the condenser. This is a law of thermodynamics, plain and simple.

Rick

jetech

Does your car have one or two pressure sensors? According to your Tech2 the pressures are ok. The system should not have shut off. Since you know you have more R134a in the system than it calls for bleed some off(in a certified recycling machine of course) and see how the system operates. Was the car sitting still every time it shut the system down?

TA_Freak

Thanks. I'll check that out.

It has one pressure sensor. I honestly think that there is a connection issue that I thought I had found before. A big clue is that the cruise control doesn't work either. I'm not able to invoke an open circuit at the fuse by wiggling and agitating wires, connectors ... etc.
The clutch turns off when the signal from the PCM pin 43 (red) goes from 0 (ground) to high - 12v.I can put a ground on the clutch relay input and energize the clutch. The head pressure has to be greater than 414 psi or less than 0 as measured by the pressure sensor.
My scan tool reports less than 414 so I don't know.

TA_Freak

No. Two days in a row, I was driving home- late afternoon.... on the highway, cruise control on, AC blowing cold. Then the cruise stops on it's own and a mile up the road, warm air blowing out of the vents; exactly the same each day.

TA_Freak

Just got home ..... AC and cruise worked the whole way from work. I replaced the fuse. I then ohmed the fuse and it's fine. WTH!??

What that tells me is that I have an intermittent open either under the fuse holder and/or the fuse holder itself.

jetech

I agree with you. Most be a broken wire or bad connection at splice S165. After the splice the problem would not shut off the ac and cruise control. I hope this is not another product of the shoddy mechanical work done prior (probing wires by piercing insulation)

pdxmotorhead

AC relay?

Did you use a real gauge set or just the can with gauges.. on R134 they should ban the cans with gauges,..
R134 spikes very quickly compared to the old friendly R12. The pressures need to be right. and the cans with gauges dont hack it.

My cheep harbor freight gauges work fine... they don't have to cost a fortune.

TA_Freak

God only knows. This isn't the first issue that I've had to resolve since the "build" from a shop. I'm sure it won't be the last. But yeah .... S165 is going to get a soldering iron on it (most likely).

TA_Freak

I wish it was as simple as the relay. I'm workiing with some good clues. One of the things that have "muddied the water" for me was the AC clutch relay not getting the ground signal from the PCM. I think I need to take care of the intermittent open.

I've got some decent Yellow Jacket gauges. You get what you pay for. I've had the cheap ones that have failed.

Biebs

“As we all know, the compressor Calls for 1.5 lbs”. - no we don’t all know!

Where did you get this info?? I found 32 ounces or 2 lbs to be the correct number.


I just recharged my AC system using the pressure method low side reading 35psi and high side reading 240psi.
your pressure reading are good.

sounds like you have electrical gremlin - to your clutch.

Good luck to finding it sounds like you are on it!!!

chrisfrost

iTrader: (8)

Hello all, The pressures depend not only how much refrigerant is in the system but ambient temp changes pressures. So a properly charged system at 80 deg fahr ambient the low side should be between 40-50 lbs. with high side at 175-210 lbs. at 85 deg fahr ambient low side 45-55 lbs and high side 225-250 lbs. at 90 deg fahr ambient low side 45-55 lbs. and high side 250-270 lbs. at 95 deg fahr ambient low side 50-55 lbs and high side 275-300 lbs. at 100 deg fahr ambient low side 50-55 lbs. and high side 315-325 lbs. at 105 deg fahr ambient low side 50-55 lbs and high side 330-335lbs. at 110 deg fahr ambient low side 50-55 lbs. and high side 340-345 lbs. I found this information on multiple websites although I do not remember any of the web address'. Good luck . I also found 24 ounces to be the correct amount of R134A in a 2002 camaro 35th anniversary Z-28 also on multiple websites.