AC Stopped Working

[WhiteFalcon]

On my 2005, the AC system stopped working (of course when it was 102 degrees outside). Here are the stats: System charged; static pressure 60 low side and 20ish high side; pressure when running 140 low side 50ish high side. No cooling even when running. The clutch air gap looks good.

The clutch does not come on unless I jump the high side pressure switch. I have not yet jumped the low pressure switch and have only done it for about minute in order to get some pressure readings when it is running.

Any thoughts on whether the issue is the compressor or the expansion valve? The compressor was running just fine one day and they the system was not working the next. Since I do have some pressure when the system is running, I'm not ready to condemn the compressor yet, but wanted to see what others more experienced with AC think about it.

Thank you for any thoughts or suggestions!

 

[Hamfisted]

Are you the original owner ? Who has ever put gauges on it, or charged it? If you have to jump the high side switch I'd say it's way over charged. Those pressures are messed up. You may need to vacuum the system down and start over. The Expy likes 30-35 psi LOW, and 225-250 psi HIGH pressures. Should give you 35-40 degrees out of the vents. Any weird racket coming from the compressor when it is running ?

 

[WhiteFalcon]

I am not the original owner, but the system was running great until Saturday and I've had it for three years and use the ac almost all year round (South Carolina). I agree that the pressures are messed up and the weird part is that it just started doing this out of the blue. That made me think mechanical or electrical malfunction. No weird racket at all from the compressor. But I do sometimes hear a soft gurgling sound coming from the evaporator under the dash. Nothing crazy, just a gentle soft noise. Rear ac has always worked like a champ.

I will capture the refrigerant and vacuum it down and start over if I have to, but it just seems like something else must be going on.

 

[Hamfisted]

Yeah, if you're not the original owner and don't know the complete history of the truck, and you're getting those kind of pressure numbers it may well be worth it to vacuum the system down and start over. Don't dump liquid R134 into the system, only refill R134 in a gas state. Take your time and don't rush the recharge. It takes a while to refill.

 

[johnboneske]

Yeah, if you're not the original owner and don't know the complete history of the truck, and you're getting those kind of pressure numbers it may well be worth it to vacuum the system down and start over. Don't dump liquid R134 into the system, only refill R134 in a gas state. Take your time and don't rush the recharge. It takes a while to refill.

only recharge in a gas state? Since when, you always charge liquid slowly...

 

[WhiteFalcon]

One question I do have on the refill is how do I refill it if the compressor is not engaging? Should I jump the low pressure switch to get it running? Or can I just recharge it without it running?

 

[Hamfisted]

One question I do have on the refill is how do I refill it if the compressor is not engaging? Should I jump the low pressure switch to get it running? Or can I just recharge it without it running?

No, do not jump the low pressure switch. The compressor will eventually kick on when enough minimal gas has entered the system. IT TAKES TIME, do not rush it. The Expy takes 54oz of R134 to fill. So you can some what measure what you've put in the system from the weight of the contents in whichever freon cans you use for the project if you don't have an actual scale to measure exactly what you've put in the system. Like if you're just using those typical 12oz cans of freon, it takes about four and a half cans to do the job. You don't shoot liquid freon into the system because the low pressure (inlet port) is a direct shot into the compressor inlet and you can cause damage to the compressor (i.e. slugging the compressor...). If you don't already have a vacuum pump to use, those HF vacuum pumps work fine for the DIY jobs.

 

[WhiteFalcon]

Thank you! I will be pulling from the can through the vacuum gauge set hanging off the hood, so it will be all gas going in there for sure. Do I have to do it while it is running? Four and a half hours of idling will be be no fun, but if that is what's needed, that is what I will do. How long should I vacuum he system?

 

[stamp11127]

Minimum is 30 minutes at 29 in of mercury. Longer is better since it will boil off any moisture in the system.

Four and a half cans of refrigerant not hours.

Are you sure you have the low and high readings correct? It makes better sense if you have them swapped.

Static pressure should be balanced on low and high side not uneven.

If you load the system with the can valve up you get gas, flip the can so the valve is at the bottom you get liquid. When the low side pressure is high enough to close the low pressure switch the compressor will come on.

 

[WhiteFalcon]

Thank you Stamp. Misread the time thing for sure.

The low is definitely higher than the high side when running (and that was only when I could get the compressor started by jumping the high pressure switch). Static pressure is closer to even, but not quite there. I am going to check it all again this evening as it was over 100 degrees outside yesterday while I was checking it.

 

[TomB985]

Sounds to me like something broke suddenly, those pressures just don’t make sense. A gradual leak doesn’t cause the system to stop working and without warning have pressures like that.

I think you’re getting ready to waste a bunch of refrigerant.

 

[1955moose]

I agree with Tom. If your AC was fine then came grinding to a halt is not freon charge. You might be off a little on R134 but you've got a part that failed. I haven't recharged AC in awhile, but I used to invert the cans while motor was running, shaking them slightly, with a red shop rag around can. My systems took around 36-39 ounces. Used to take about 30 minutes give or take. The fact you've got to jump the switches tells me either you have a bad switch, or something's amiss with wiring. Your getting voltage to the switches or jumping them wouldn't work. This is kinda out there, you might check the grounds feeding those switches. One loose or broken ground would do it.

Sent from my N9131 using Tapatalk

 

[stamp11127]

The only way you can build that high of pressure on the low side and have low pressure on the high side is to have failed valves in the compressor.

The odd thing is the high side switch should be closed normally and open with high pressure. You shouldn't have to jump it.

 

[WhiteFalcon]

Ok, now I’m completely baffled. The static pressure is 100 both high and low side. This is within spec since the outside temp is 100 degrees. Relay and fuse are fine. Still will not turn on. When I get the compressor running by jumping the high side switch, it does not get cold and the low side is 55 and the high side is 155. So I have pressure and the gas seems to be moving through the expansion valve. Yet it does not cool. What am I missing here?

 

[1955moose]

I think Stamp nailed it with the compressor. Changing it is a tough job though, about 4 hours. Maybe you can have a reliable shop in your area troubleshoot it, then you do the repairs. Some shops will even evacuate your freon, then replace it when your done with repair, for a small fee.

Sent from my N9131 using Tapatalk

 

[stamp11127]

Don't condem the compressor yet. His low/high side pressures have swapped. How about that...

Where is the switch located that you are jumping? Near the condensor or in the accumulator?

 

[1955moose]

That's why I suggested have an AC shop diagnose first.

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[WhiteFalcon]

Stamp. The switch that I am jumping is the high side located near the passenger headlight.

 

[stamp11127]

The high side switch is a NC (normally closed) switch, opens when a preset pressure is exceeded. Since you have to jump it that means the switch is probably bad, test with a meter to make sure. Which ac option do you have - manual or EATC?

Here is a link that covers your problem. Two possibilities, failed txv or bad compressor. Either way you need to recover the system and inspect/replace the txv for starters. If that isn't it then change the compressor & drier.

 

[WhiteFalcon]

I have EATC. I ran through all the electrical possibilities tonight and it came down to that high pressure switch. The compressor works when the high pressure switch is jumped. I’m wondering if there is some gunk in the system that clogged the expansion valve and pushed the high pressure side out of wack and tripped the switch. Now the switch is stuck open. My pressures are back to normal tonight. This is really weird. I’m guessing that changing the switch will require emptying the system, right? Thank you for the video link!