AC cold enough?

[Dennis_H]

I had my compressor and condenser replaced in Jan/Feb timeframe. Haven't really needed it much since then till lately. Seemed to be not quite cool enough, so I put a set of gauges on it and pressures looked a little low at 85 degrees outside air. Was about 45/175 pressures. I added a can of 143a and the pressures went to 50/210 or so. I think it was better, but today it was about 95 degrees. Vent temps are somewhere in the mid 50s, I put the gauges back on and pressures were still about 50/210 at near 95 degrees agter running for 30 min driving.

Does this seem a little too warm at the vent? I think the 2010 is an orifice tube system, not a TXV. I have some experience with home HVAC, but I don't think you use superheat/subcooling numbers to fill auto units, right? Too many variables in heat load, compressor speeds, fan speeds, etc., correct?

Maybe that is all it can do at 95 degrees out, but my wife's Hyundai will freeze you out.

Thanks.

 

[stamp11127]

Look at your gauge set, one of the scales should be temp. This will show you what the evap temp will be. I usually run the low side around 35-37 psi, high side 200 to 225 when the ambient temp is 85-90 degrees. This will keep the low side just above freezing.

See what your static temp is in the morning before cranking the engine. It should be very close to ambient temp. Auto ac doesn't use superheat/subcooling. The amount of refrigerant is by weight.

 

[Motorcity muscle]

Just a suggestion, to fine tune the refrigerant charge I put a digital thermometer in the supply vent inside and run the meter out under the hood. Small adjustment up/down to reach lowest temperature. Correct way would be weigh in charge with digital scale to manufacture spec. Have found the dual systems like a bit more than stated weight.

 

[1997SCEBFEX]

no expert here, but seems warm to me as I have 39* out of my front vents after running for a while using an analog food thermometer which stays in the driver's side (left of wheel) vent.

however, when in the high 90's and more, 50* is sometimes appreciated when climbing in after being out in it. my truck is oem torch red, so it gets warm inside. when I drove cross country years ago in July, I did have to adjust the thermostat wheel a bit toward 11 o'clock, or so, to make it comfortable up front. however in the back, the two Labs enjoyed the snuggling colder temps.

let us know if you find something else.

 

[johnboneske]

Low side should be 50 to 55 and high should be 275 to 300. There is no super heat/super cool with auto AC units.

 

[Dennis_H]

I haven't given up on this issue (or the thread). I have just had too much other stuff happening. I do have a couple clamp on thermocouples coming in to I can measure the line temps much more accurately. I'll know more then.

Given that my low side is 50 and high is 225-250, If I decrease the levels to drop the low pressure side to 45, that will also decrease the high quite a bit. I was at 45/175 at 85 before I started playing. Added 12 oz to get to the 50/225 that I thought would be better. I curious how Stamp11127 gets 35/225 at 85 to 90 degrees.

 

[stamp11127]

It's a secret.....may be memory error also. I know we do keep the evap just above freezing.

The students are starting the A/C class next week. Once they get through the classroom/theory of how it works they go out into the shop and work on trainers then their vehicles, mine included. At that time I will take some pics of the gauge readings and pertinent temp readings and post them.

 

[Dennis_H]

That would be fantastic. Thank you doing that.

 

[gixer2000]

I'll bet your overcharged now. Get that low side down around 40 ish. That'll give you a 35° ish evap temp and should about right. Adding more refrigerant doesn't mean you going to make it colder and a PT chart needs to come into play when your guessing.

 

[Dennis_H]

I thought I was a little overcharged and backed it down a bit and seems to run about 45 - 50 at vent now at 95 degree outside air temp. I knew the guy that filled it originally after compressor went out went by volume when he filled, but also used cans with dye. I have seen that the dye is counted as part of the volume of the can, so I thought I needed some more refrigerant. It turns out I did need some more, but not 16 oz more... It may still be a hair over, but pretty comfortable now. It really takes a fairly small amount for a dual system. I had a full size van with dual air and it held quite a bit more.