AC optimal temp?
Chronic Tool Dropper
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From: Bend, Oregon
The discharge temp at the vent should be about 25ºC or about 40ºF below the temp of the air entering the evaporator, as Tails describes above. So check the air temp on the floor as well as at the vent. With engine at 1500 RPM and good airflow through the condenser, cabin fan on speed 2. Humidity is a big factor too, since cooling capacity is spent condensing the water out of the cabin air. Capacity spent condensing water is no longer available to pull heat from the air. Of course, dropping the dew point as the water is extracted makes the air feel cooler on the skin.
To answer your question, I see cruising vent temps under 20ºF, with fan on 2 and ambients over 90ºF. We live in a coastal desert with henerally low humidity, so I have a jumper around the freeze switch. With the freeze switch in the clutch circuit, the vent temps cycle between 35 and 39 degrees. This is with the R-134a conversion.
How many folks actually use the temp slider to set cabin temp in the summer? I leave the slider at 70º and let the system do its job. And it does, black car in Los Angeles.
To answer your question, I see cruising vent temps under 20ºF, with fan on 2 and ambients over 90ºF. We live in a coastal desert with henerally low humidity, so I have a jumper around the freeze switch. With the freeze switch in the clutch circuit, the vent temps cycle between 35 and 39 degrees. This is with the R-134a conversion.
How many folks actually use the temp slider to set cabin temp in the summer? I leave the slider at 70º and let the system do its job. And it does, black car in Los Angeles.
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From: Madrid, España
Never had coming issues in my GTS neither in Texas nor in South Spain (where I live now). AC needs about a can of R134a every the years.
In Texas the AC used to freeze up the outside of my windscreen on very Gummis mornings.
IMHO jumping the freeze protection switch will only work for a short time. Without the switch the evaporator will turn into a block of ice. Especially when the car is driven in the highway for a long proud of time. All of a sudden there will be no airflow regardless of fan speed setting.
In Texas the AC used to freeze up the outside of my windscreen on very Gummis mornings.
IMHO jumping the freeze protection switch will only work for a short time. Without the switch the evaporator will turn into a block of ice. Especially when the car is driven in the highway for a long proud of time. All of a sudden there will be no airflow regardless of fan speed setting.
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Race Car
Joined: Dec 2006
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From: Tampa Florida
Hate to ask here but my FREE 87 924s I am getting mixed information. Manual says 40 degrees will go higher idle. This is the after market dealer install unit and swings 20 degrees from 40 to over 60 in the Florida heat. I had the compressor sealed changed the expansion valve new parallel flow condenser flushed and charged to 24 oz on a r12 30 oz system.
When cold 22/145 40 degrees
Warming up @ idle 45/125 50 degrees
Fully warm 52/130 60 degrees
When driving gets close to 40 degrees
Rebuilder said my compressor was good I think it is weak is this a 924 thing or a bad compressor? Lower high side pressures indicate a bad compressor water on the condenser does not drop the temp.
When cold 22/145 40 degrees
Warming up @ idle 45/125 50 degrees
Fully warm 52/130 60 degrees
When driving gets close to 40 degrees
Rebuilder said my compressor was good I think it is weak is this a 924 thing or a bad compressor? Lower high side pressures indicate a bad compressor water on the condenser does not drop the temp.
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Chronic Tool Dropper
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From: Bend, Oregon
<<...>>
IMHO jumping the freeze protection switch will only work for a short time. Without the switch the evaporator will turn into a block of ice. Especially when the car is driven in the highway for a long proud of time. All of a sudden there will be no airflow regardless of fan speed setting.
IMHO jumping the freeze protection switch will only work for a short time. Without the switch the evaporator will turn into a block of ice. Especially when the car is driven in the highway for a long proud of time. All of a sudden there will be no airflow regardless of fan speed setting.
Leaving the jumper in place allows for much faster cabin cool-down, critical especially if the car has been parked out and the body is heat-soaked. Like most folks, the majority of my 928 use is for rides less than an hour in duration. We've never had a problem with ice-bricking the evaporator in that short a time. I have needed to shut off the compressor a few times on extended (3 hours or more) drives north along the coast. That lets it thaw out some, but it takes a while. So if I know I'm going on a longer ride, especially where the humidity might be high, I just reconnect the freeze switch.
Burning Brakes
Joined: May 2001
Posts: 1,124
Likes: 11
If you require a good description on car air-conditioning, google the following:
"Ariazone" Automotive & Industrial Refrigerant Service Equipment, to get a copy of their Automotive Air Conditioning Training Manual.
"Ariazone" Automotive & Industrial Refrigerant Service Equipment, to get a copy of their Automotive Air Conditioning Training Manual.
Race Director
Joined: Sep 2004
Posts: 16,271
Likes: 82
From: Stockton, CA
I can't speak for R134....but when I got Sharky's R12 system working properly I would regularly see greater than 50F under ambient.... Typically I would see close to freezing from the main vent....at times 28f..... it appears my "freeze" protection would not turn "on" until around this threshold.... Bill Ball had similar readings from his 1989 as well....
Drifting
Joined: Jan 2010
Posts: 3,334
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From: Nebraska
I have never measured mine but it does freeze me out quick in the hottest weather. I can turn on my front and rear on full blast and be cool almost instantly. Less than one block on even the hottest days with a black interior. I know r134 can be made to work but I sure love my r12.
Race Car
Joined: Dec 2003
Posts: 4,477
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From: Atlanta, GA
Hate to ask here but my FREE 87 924s I am getting mixed information. Manual says 40 degrees will go higher idle. This is the after market dealer install unit and swings 20 degrees from 40 to over 60 in the Florida heat. I had the compressor sealed changed the expansion valve new parallel flow condenser flushed and charged to 24 oz on a r12 30 oz system.
When cold 22/145 40 degrees
Warming up @ idle 45/125 50 degrees
Fully warm 52/130 60 degrees
When driving gets close to 40 degrees
Rebuilder said my compressor was good I think it is weak is this a 924 thing or a bad compressor? Lower high side pressures indicate a bad compressor water on the condenser does not drop the temp.
When cold 22/145 40 degrees
Warming up @ idle 45/125 50 degrees
Fully warm 52/130 60 degrees
When driving gets close to 40 degrees
Rebuilder said my compressor was good I think it is weak is this a 924 thing or a bad compressor? Lower high side pressures indicate a bad compressor water on the condenser does not drop the temp.
Dan
'91 928GT S/C
475hp/460lb.ft
Three Wheelin'
Joined: Dec 2011
Posts: 1,413
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From: NW Indiana
As of today I'm running about 37º out center vent after 10 minutes of pulling out of garage. 90+ outside. Side windows sweating like a pig on the outside. Running R500 simply because I have a rather large amount of it. It has about 15% more capacity than R12.
