How cold should your a/c be?

Messages
172
Location
Laurel, MD
It's been 90+ degrees the last few days and I'm not sure the a/c in my truck is performing as it should. I drive home from work (40 mins) and have to keep it on the coldest setting at full blast the whole way. It's not hot in the cab, but it's not freezing either. Is it because it's so hot outside, or does the system need work?
 
Messages
1,979
Location
Houston
get a small thermometer and check the outlet temperature (center dash vent, recirculate, medium fan). It should read under 40f, preferably under 35f once everything is going. If it is over 40f, you are probably low on freon. Also if it gets a lot colder with higher engine RPM, you are likely low on freon. btw, always drive for a few minutes with all the windows down and the AC on and NOT on recirculate, fan at max; to at least get the cab and all the ducts down to 90f. After a minute or 2, close the windows and switch to recirculate. I drive thru the parking lot before I close the windows and switch to recirc. Let the AC cool down the 90f air instead of the 140f air.
 

speedy341

Thread starter
Messages
172
Location
Laurel, MD
I feel like a total dumba$$. It's not on recirculate. This is the first vehicle I've ever had with working a/c (although they all HAD a/c, none worked). There's 5,000 miles left on my warranty so I'm paranoid about ANYTHING going wrong.
 
Messages
22,188
Location
Colorado Springs
My A/C wasn't working quite well when I bought my car, although a repair facility measured it with a thermometer and it was within spec. So I bought some of this stuff along with their High Mileage top off, and installed both products. I also bought a guage to measure the pressure. Pressure went up from the bottom of the good to the middle/top and my A/C is like a freezer now. Works great!
 
Messages
756
Location
Northern California
It gets hot here in Sacramento in the summer w/ 90-100 consistently. I tend to run the AC occasionally off season just to keep the seals good and to keep the components in the system lubricated. The AC works fine, even w/o the recirculate
 
Messages
191
Location
midwest
If I remember correctly, the proper procedure for checking the A/C output is inserting the thermometer in the center vent, recirculate, fan set on high, engine at 2200 RPM. Ideally, the temp. should be around 40F. On a hot day (100+ F, high humidity, etc) a perfectly functioning A/C system may not be able to put out air colder than 47-50F. I haven't spent a whole lot of time in the business, and the time I did put in was almost 5 years ago, but I have never seen for myself, or heard of, an automotive A/C system putting out air colder than 35F. Running the A/C system once in a while for a few minutes in the off-season is an excellent idea. However, owners of late-model (model year 1995 and up, I believe) vehicles do not need to perform this function, since A/C compressor engages every time the defrost is on.
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by Russ: If I remember correctly, the proper procedure for checking the A/C output is inserting the thermometer in the center vent, recirculate, fan set on high, engine at 2200 RPM. Ideally, the temp. should be around 40F. On a hot day (100+ F, high humidity, etc) a perfectly functioning A/C system may not be able to put out air colder than 47-50F. I haven't spent a whole lot of time in the business, and the time I did put in was almost 5 years ago, but I have never seen for myself, or heard of, an automotive A/C system putting out air colder than 35F.
To do it right you measure the air temperature into the AC and out and the humidity as well as running the engine and AC fan under specified conditions. Then you look up the correct values in the shop manual and compare. I agree on the 35F, if the air is that cold, then ice is likely forming on the coils because they are several degrees colder than the air. 40F is more realistic number. When my S15 was nearly new the AC was real weak. It wouldn't keep the cab comfortable on a 95 degree day with low humidity. The Service Pimp said "they all do that now that we have to use R134, you can't expect them to work on a hot day." I went back a few days later with digital thermometers in the AC air intake and outlet and the factory performance table taped to the dashboard. After I drug the Servie Pimp over and showed him the readings and shop manual pages he called their AC tech out to check it. This was a major GMC Pontiac dealer. The tech asked if he could borrow my digital thermometers because they didn't have any good thermometers [LOL!] [LOL!] Turned out the tech was not only honest he was competent and diagnosed the problem as a bad sensor that allowed the evaporator to get too cold and freeze over. After he fixed it, it would keep the cab comfortable on the 2nd lowest fan speed on a 105F day.
 
Messages
275
Location
Florida
[Off Topic!] Here in Miami i tinted all my windows to a median dark and on even the hottest days when heat index is 110 which is almost every day in the summer i can keep the A/C on the lowest speed ounce the car cools down.It makes a ton of differnce.When i'm in a car with no tint i fell like i'm burning up. [Cool]
 
Messages
1,908
Location
Fort Worth, TX
Search AC questions around here for other boards mentioned specializing in AC questions. I can't recall the two I use. You'll find some mighty good answers (and questions you hadn't thought to ask). Strongly advise against any DIY. Auto HVAC is a specialty for a good reason.
 

rcy

Messages
1,600
Location
Burlington, Ontario, Canada
quote:
Originally posted by TheTanSedan: Search AC questions around here for other boards mentioned specializing in AC questions. I can't recall the two I use. You'll find some mighty good answers (and questions you hadn't thought to ask). Strongly advise against any DIY. Auto HVAC is a specialty for a good reason.
www.aircondition.com
 
Messages
39,805
Location
Pottstown, PA
quote:
To do it right you measure the air temperature into the AC and out and the humidity as well as running the engine and AC fan under specified conditions. Then you look up the correct values in the shop manual and compare.
Yes, my 99 FSM for my jeep mentions no # numbers ..and only offers this method for a recharge. @70 ambient > Evap inlet port: 26-35 psi > Compressor discharge port: 180-240 psi > @80 > E: 32-41 > C: 200-260 > @90 > E: 38-47 > C: 250-300 > @100 > E: 44-53 > C: 270-340
 
Messages
39,805
Location
Pottstown, PA
On an R12 system your evap temp is just about the same as your evap pressure. We used 30° as a target outlet temp. Yes, if you left the windows open on one of those systems ..the evap would surely freeze up.
 
Messages
1,979
Location
Houston
I still think 40f is too warm for an outlet temp. We used to measure 35f all the time on commercial systems, never had any ice issues as long as there was air movement. If there's no air movement ice is the least of your worries.... Measured all 3 cars this weekemd; it's Houston, it's 95+f and incredibly humid. All discharge well under 40f, one at 35f consistently and that's the original factory charge on a 02 highlander. One is r12; 2 are r134a.
 
Messages
709
Location
CT
The A/C Test for my 00 Saab reads: - doors, windows, hood must be closed - all panel outlets should be open - engine speed must be 1,500 to 2,000 rpm - ambient temperature must be 20-25°C (68-77°F) Auto Climate Control Settings: Fan speed: MAX Temperature: 'LO' Air distribution flap: 'Panel' manual selection Check the temperature 50 mm inside the center panel outlet. Read the temperature after 5 minutes. The temperature should be below 7°C (44.6°F) So I guess the proper temp depends on application.
 
Messages
661
Location
Bosphoria
quote:
Originally posted by Razl: So I guess the proper temp depends on application.
Sure... On my Chevy they give an absolute value up to 80 or 85ºF ambient temp. Higher than that they go relative, specified a drop for every 10ºF increase in ambient temperature. So I guess, there is a limit an AC can isolate you regardless the ambient temperature.
 
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