A/C recharge - high and low pressures?

[Fullboogie]

The A/C on my 2007 is getting a little warm, so I need to recharge the system. I have R134 and a manifold/gauge set. What pressure on the low and high side do I need to shoot for when recharging? Didn't see any reference to this with a search.

 

[RazorbackMustang]

The pressure depends on the ambient temp. I don't have the chart on my phone. NAPA has a nice chart that you reference. Generally, if it takes gas from the low side, it needed a little. When it stops sucking gas, it's full.

 

[Fullboogie]

Thanks - I understand about ambient temps. Need a pressure chart so I can recharge.

 

[Eel Mit]

Are you vacuuming the system down? or just pumping in over air?

On an evacuated system, 80-85deg ambient temps, big fan on the condensor...shoot for 50psi lo, 220-250psi high.

Usually gets 45-48deg out the vents in nasty humid Texas air.

 

[TexasBlownV8]

I usually just use the low side, and hook up the high side only if there is a problem (to detect a restriction or pump issue).
Low-side pressure with a/c running should be between like 28-45 or so (IIRC, that is the range of the pressure switch, which I looked up a couple weeks ago). I topped of the charge on my '06 at 36-37 psi at 80-85*, about in the middle of the pressure switch range.

Just a reminder, when you add freon, you want to make sure you don't introduce air through the gauge hoses. Of course there's ways to do that.

 

[Weou09]

Ok, first if you lost Freon you have a leak. I'd vacuum it down first. The amount of oil and refrigerant is on the radiator support. I go by that before i worry about pressures. They are really only for diagnostic. But as mentioned 45-50/200-250. I see around 40° at the vents. I've had great results with the leak fix stuff they have at Wal-Mart for small leaks.

 

[HABU06GT]

R-134 refrigerant pressure is relative to ambient temperature and nearly 1:1 temp/pressure and is also how we check for contaminated refrigerant 89 degrees outside should be VERY close to 89 psi in the tank and any signifigant difference up or down would indicate contamination. Depending on ambient temps your system pressure should be between 35-40 on the suction (low) side and 145-175psi on the pressure (high) if you have a system going close to and above 200psi you have an issue/restriction (or its a DAMN HOT day). Yes defiantly check for a loss if you need a recharge. systems will not always just stop when they are full, a lot of times systems will stop short and they have to be "tricked" into pulling the rest of the charge in. the BEST way to recharge a system is to evacuate/recover, pull vacuum down to 30ing (negative pressure, vacuum duh lol) and recharge to factory spec by weight, second best method is by pressure at gauge although gauges are your greatest barometer and tell you EVERYTHING the system is doing or not doing. and yup 40 at the vents is very good 35 degrees at the vents and your nipples will shred your shirts are your lines frosting/freezing, is the pump engaging?

 

[Fullboogie]

Yeah, got an issue. Pressures are 15-20 low side, 125-140 high side. It won't pull a charge, because the compressor is on for one second, off for two, on for one, etc. It's either too low on freon to keep the compressor running, or the low pressure switch is bad. Anybody happen to know where the low pressure switch is on a 5.4?

I'm so reluctant to take it somewhere because I know I'm going to get fucked with all kinds of bullshit repairs.

 

[Weou09]

You can jump it and make it stay on that way. But if your LOW, you have a leak.