What temperature does your a/c blow

searched.
I just bought my '01 60th Anniversary. My last rig was R-12 and with a thermometer in the dash vent it would blow 29* F on a 95* F day. My new rig is of course R-134 and blows at 39* F on a similar day. Is this normal, what temp are you guys getting?

It hsoudl be a tad lowe rin temp, but only by a couple degrees....

The air should be at around 33-35 Degrees at the vents (at less than 32 you risk freezing the evap core). You may also have some frost come out to when it is that cold......

Who measures AC temps?? It's either cold, or not cold....

People who are uber picky or those that are ASE certified in A/C...

IE: ME!

In all truth, the temp is a good indication of the systems overall health.....

Your last rig had something wrong with the AC or there was something wrong with your thermometer. The FSM should have a discharge temp at the vents, but, like mentioned, if the air out of the vents is 29°F, then the condenser is even colder and would likely ice over in humid conditions. Like mentioned, the temp of the air out of the vent should be 33°-36°F.

R-12 only has a slight performance vantage over R-134a, but they condense and evaporate at different temperatures/pressures. So, the AC system has to be tailored to properties of the refrigerant that will be used in it.

So, its common for a R-12 system that has been retro-fitted with R-134a to perform a little worse (some actually perform as well, even a little better, and some far worse) because your using R-134a in a system tailored for R-12.

BUT, your new rig's AC system was tailored for R-134a, so it should perform just as well as any R-12 system. So, its likely your new rig's AC system is probably in need of some checking and probably servicing, if the temp is higher than it should be.

R-134a is a smaller molecule than R-12, so R-134a system leaking down is a little more common than the older R-12 system. Tighten up all the fittings on your AC system, check the high low pressures and add some R-134a if necessary. Take it too an AC shop if you don't have the tools and knowledge to do it. BUT, my guess, your probably down a couple ounces on refrigerant.

'03 with low 30's at vent and '88 (R-12) with low 30's at vents. R-134A should be about the same IF the cooling system is designed for it-- retro-fit kits will be warmer (usually) because they were designed for lower operating pressures and more efficient refrigerant.

im wondering if anybody has confirmed the accuracy of their thermos? ice water should read 33 a/c should read mid to high 30s

My thermo is digital, so it's usually right on...

My A/C in my '87 is shot, short cycles, and only 50 (ambient is 60-65) degrees at the vents......

Mine usually blows in the 80 degree range on a hot day.

Ive got a '91 with 134A and it blow about 70 degrees at the vents in 90+ weather. Ive checked the pressures but I cant remember off hand what they were. Does anyone know what the pressures should be for 134A both high and low? Im almost sure that the comp. is bad. Im going to replace it soon. Any help would be awsome.

kennzz05 said:

im wondering if anybody has confirmed the accuracy of their thermos? ice water should read 33 a/c should read mid to high 30s

Click to expand...

The first thing I checked was the Thermometer, but I checked it against another one that I have, I suppose it's possible that it is off, but I don't think so. What would be a sure fire check of it, what do I know is a certain temperature?

My center vent blows around 42-44 Degrees when the outside air temps were near 100 Degrees F here about 2 weeks back in OK. That is w/a nice certified thermometer stuck in my center air vents.

It should be colder, but since I'm not an AC expert I'm not sure I want to mess w/it. I did add a little refridgerant to it about 1 month back and noticed an immediate improvement in how fast the temps dropped, but I'm not sure I want to push my luck or overfill the lines.

My wifes Libby gets COLD and QUICK when compared to my '96 XJ. 'Course my XJ has a LOT more air leaks and such thru the windows and what-not too...

I keep a thermometer in my front vent... On a good day it's between 40 and 45.

Most R-134a systems run 150-225PSI on the high side, with the pressure being higher, the higher the ambient temperature; roughly for most systems, 68°F Hi-side should be 150-180 PSI, 98°F Hi-side should be 190-225 PSI. Some system can surge up to 250 PSI for short times at really hi ambient temps. For most systems, if you getting a steady hi-side over 250 PSI even if it is 98°F ambient, its likely the system has too much R-134a in it.

The low depends on how the system is controlled, simple pressure switch, should be 25 PSI maybe bounce up and down a couple of PSI. If the evaporator is equipped with a temp probe, then you can see the low side drop to 15-25 PSI. Less than 25 PSI in R-134a should produce less than freezing temps, I guess if you have a temp probe, they set the system up to drop below 25 PSI to cool down the evaporator quicker to desired temp, once the evaporator surface actually hits 32°F, then it cycles off the compressor to keep the temp from dropping lower.

Remember, your suppose to measure with the AC at max load, windows open, ac on max in recirculate mode, engine is suppose to be off idle as well, up at 1000-1500 rpm.

Redsnake said:

My center vent blows around 42-44 Degrees when the outside air temps were near 100 Degrees F here about 2 weeks back in OK. That is w/a nice certified thermometer stuck in my center air vents.

It should be colder, but since I'm not an AC expert I'm not sure I want to mess w/it. I did add a little refridgerant to it about 1 month back and noticed an immediate improvement in how fast the temps dropped, but I'm not sure I want to push my luck or overfill the lines.

My wifes Libby gets COLD and QUICK when compared to my '96 XJ. 'Course my XJ has a LOT more air leaks and such thru the windows and what-not too...

Click to expand...

Adding refrigerant without checking superheat as you charge is just asking for trouble...
This is measured by comparing the suction pressure on a PT chart to the leaving temperature of refrigerant at the outlet of the evaporator....
Most systems recommend a 10-12* superheat to be properly charged....

I have alwasy kept a calibrated HVAC thermometer in the vents of all my vehicles. I send it out every 6mos. to be calibrated by a lab. Luckily with the work I do, we have to send alot of equipment out every 6mos. for cal. by a lab and I get my thermometers done for free
As stated, it is an easy way to always know the health of the system. In my '00 the temp is running right at 39° with ambient temps in the low 90s.

Also as previously stated, the best way to check a thermometer for accuracy is to place it in a glass of ice water and take a reading. Should be @ 33°. Digital/analog it doesn't matter.

Mid 40's on recirc and high fan after about 10 minutes of driving if I'm stopped in traffic it goes to 50F. These temps are @110 F outside with humidity in the low teens.

I have yet to see any R-134 system that could keep up with a decent R12 system. I've seen several R12 systems that would blow in the low 30's on high fan, when it was 110 outside. I have never seen a R134 system that could do that. I guess the systems have also gotten a lot smaller and consume less power then the older systems.

Depends on ambient temp. On a 90* day I'd guess it blows about 95*.

Evaporator temps are usually at least 5 and can be as much as 10 degrees or more colder than the exiting air temps. You build some amount of ice on your evaporator at exiting air temps in the low 30s, but usually not enough to block it. That's one of the reasons why you'll see a larger than normal sized water puddle underneath a few minutes after you've shut down from a long cool trip.

Can anyone Tell me how much Oil and Freion an 134A system needs? Also what type of oil? PAG?? PAO??