For those with upgraded AC systems, what should typical vent temps be?

[deputydog95]

My car is in for basic maintenance service and I'm having them service the AC while it's there. I've replaced the entire factory AC system with the Classic Auto Air kit.

What temperature should I expect to see from the center vents on high?

[GH85Carrera]

I know that is where most people measure the temps. I can't get a thermometer to just hang there as I drive. Normal driving conditions is the real test. I had an 1985 Carrera, and the little bitty vent on the sides of the dash. I can slide a standard AC temp gauge in that as go for a drive. It will blow 38 to 40 degree air from that vent at full high speed blow on a 100 degree day. Even after stopping for lunch and the car sits in the sun for an hour. Get in, go and 15 minutes later that side vent is blowing cold. The center vents blow so much air with the upgraded fan kit I bought from Griffith's I have to divert it away from my face if I have it max cold and getting 38 to 40 degree air.

My ultimate winning moment was in Savannah, GA in August, full sunny day and stupid heat index. My wife asked me to turn the temperature up because she was cold on a lunch time trip.

I have the four condenser Griffith's system, and the variable speed fan switch and his hurricane blower. His stuff is expensive, but top quality.

[T77911S]

i have his evap and front and rear cond,.
40's maybe 50.
that's driving with fan on hi, BUT I have to turn the temp up because the evap will freeze over.

people will say they get down in the 30;s or even 20's but a proper system should never get that cold BCAUSE of the evap freezing over and the low side pressures can get too low.
the 911 does not monitor the low side like most cars do, they just use an evap temp probe to "control the low side" not the best way to do it.
part of the reason you can get down to 30 is if you set the fan speed to low and/or the air flow over the evap is low, in part due to the low CFM out of the stock fan.

you also need airflow over the condensers to get proper or accurate temps.

[Jack Stands]

It would be helpful to see what temps folks see with a properly functioning factory system in comparison.

[blucille]

a lot of folks measure with an IR/laser infrared thermometer. It simply won't be accurate. These things are designed to measure the temperature on a surface, not air temperature. Mine showed temps well below freezing, 20 degrees F at times. It was suffering from a thermal shock condition. Instead, I used an instant read analog kitchen thermometer in the center dash vent.

I've got the full Kuehl/Griffith's kit too, 4 condensers, the high efficiency evaporator, the upgraded fan/blower. Running R-134a, which won’t cool as well as R-12.....you’d be hard pressed to get R-134a to give dash temps below 40 degrees, in even a modern car. From my in-dash thermometer I get temps right around 40 degrees, occasionally a 39, most often a 41-42, fan on high, car in motion, system running for a few minutes or a few hours.

Lots of compromises here, and I’m sure lots of variables in terms of how temps are being measured, ambient temp, relative humidity, choice of refrigerant, methods of measuring temps.

[Flat Six]

For a point of reference, my stock (r134a conversion, ND compressor, factory condensers & evap) runs 48-50 degrees at the center vent w/fan on high and car in motion. That's with a fresh charge and ambient temps here in the LV valley at low triple-digits right now.

[scarceller]

Try contacting Charlie at https://griffiths.com/porsche/air-conditioning/ one of the best sources for 911 AC info.

[wrxnofx]

Originally Posted by Flat Six

For a point of reference, my stock (r134a conversion, ND compressor, factory condensers & evap) runs 48-50 degrees at the center vent w/fan on high and car in motion. That's with a fresh charge and ambient temps here in the LV valley at low triple-digits right now.

What amount of R134a do you put into the system? The full 47.8oz or whatever it shows on the sticker for R12? Or a smaller amount than that?

[Rawknees'Turbo]

It's always good for a laugh to see posts from peeps who apparently can not build a genuinely cold a/c system so then declare that it is either not possible, performance testing is flawed, or it is actually a negative to have super low vent temps. I heart Pelican a/c threads!

[walt]

I have the full Griffith upgrade and can get sub 40 temps on a hot day with the middle fan speed. Using his improved performance evaporator fan the temps do increase slightly with the higher fan speed.

[RNajarian]

Originally Posted by Rawknees'Turbo

It's always good for a laugh to see posts from peeps who apparently can not build a genuinely cold a/c system so then declare that it is either not possible, performance testing is flawed, or it is actually a negative to have super low vent temps. I heart Pelican a/c threads!

You tell them Rawknees!

[Rawknees'Turbo]

^^^

I thought of you when I posted that (#forum bromance), as there are several members (not like THAT! ) over the years that have posted super low vent temp systems that actually work - no way are we all liars, dumbasses who can't measure temps, or operating systems that freeze up regularly and then don't work worth a dayumn.

[JMS935]

Originally Posted by Rawknees'Turbo

It's always good for a laugh to see posts from peeps who apparently can not build a genuinely cold a/c system so then declare that it is either not possible, performance testing is flawed, or it is actually a negative to have super low vent temps. I heart Pelican a/c threads!

The better laughs are the guys stripping out their AC systems to save a few pounds with their puny N.A. motors. Those are the threads I find hilarious. To sacrifice all that comfort for what’s probably so negligible in added performance that you barely notice it if at all. At least they’ll lose weight sweating their asses off, so that’s another weight savings bonus as well.

[GH85Carrera]

If your evaporator is freezing up, your temp probe is not properly located. I just this spring put in Griffiths bigger blower. When I put the probe back in I made sure it was properly located, and I used a small dab of thermal paste. I have his variable speed fan switch as well, and that comes with s LED that indicates if the compressor is running. I can see the temps get down to high 30s and the compressor kicks off. No more freeze up. Before I could get freeze up, but I just dialed the temp back and kept it from freezing. I figure either way if the evap is just above freezing, it is max cold.

[RNajarian]

Originally Posted by Rawknees'Turbo

^^^

I thought of you when I posted that (#forum bromance), as there are several members (not like THAT! ) over the years that have posted super low vent temp systems that actually work - no way are we all liars, dumbasses who can't measure temps, or operating systems that freeze up regularly and then don't work worth a dayumn.

To be fair those sub freezing temperatures are with a cool system (not a cool day, see first photo on top- thermometer to right indicating outside temp is 107F) once the system warms up I’m in the hi 30’s to 40’s

I don’t sustain meat locker temperatures as long as Rawknees, his system is better designed.

[Buckeye]

I have replaced all my a/c components except the rear condenser and added a Griffins rear fender condenser. I use r12 Freon and it blows 29 degrees on a 90 degree day. Do your self a favor and find some r12

[Jonny H]

If you are running R134A and it is 100F ambient, then any AC pressure chart will show a typical low side pressure of between 50 and 50 PSI. If you cross reference that pressure with the boiling point of R134A you will find that the boiling point is in the range 45 to 51F. That’s inside the evaporator. You will lose some of that in exchange with the air and on the way to the vent.

Some people are either defying physics or not running R134A or perhaps....

[Steve Marshall]

What's a reasonable vent temp for modern car? I'm redoing my 86 Carrera AC and was curious what vent temps should I shoot for? So I drove my 2018 Buick Regal Tourx around Austin today with a thermometer stuck in the vent. Outside temp was in the mid 80's and vent temp was between 43 and 45 consistently. It's got that shut-off at a light feature and temps would hit 60 until I was under way.

[Jonny H]

^ mid 80s would be a pressure of ~40 PSI corresponding to a boiling point of ~45F. So pretty much exactly your readings.

Normal cars seem to adhere to the rules of the Universe.

[Koizumi]

Yes, we all wuv AC threads...

I’ll
throw
this one in to the pile:

Forget r-134 and r12

Try industrial grade Enviro-safe.

Colder than r12!

Significantly less pressure on the compressor!

Ok, I’m eating popcorn and I’ve bookmarked this thread