Automotive Air Conditioning Information Forum (Archives)
What should vent temp be on a 102 degree day? Pages: 12
torque395 on 
Mon August 01, 2011 5:17 PM 
Year: 1996
Make: Chevy
Model: Suburban
Engine Size: 6.5L
Refrigerant Type: R134A
Ambient Temp: 102
Country of Origin: United States
What should my vent temp be on a 102 degree day? Mine are 80 degrees at idle, 70 while driving. I know the truck needs a better fan (has a clutch fan, a supplemental electric fan would help alot).
The truck doesnt really get all that cool on short trips around town. I suspect my vent temps would be even lower on the highway. I do believe the problem is airflow related, but i also think these temps are "acceptable" given the outside temperature. I just think it could be better if it wasn't relying solely on a clutch fan. The clutch fan is old and high mileage, but it does roar a little at startup (not like it does when it gets hot) but it roars like crazy at 200 degrees (engine temp)
Let me know what you guys think....
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
70monte on Mon August 01, 2011 6:46 PM
They should be lower than that. Both of my 98 chevy trucks will be in the 40's or low 50's when it's that hot out.
I would definately get a new fan clutch if yours is old and has high mileage.
Wayne
Cussboy on Mon August 01, 2011 8:21 PM
QuoteOriginally posted by: torque395
What should my vent temp be on a 102 degree day? Mine are 80 degrees at idle, 70 while driving. I know the truck needs a better fan (has a clutch fan, a supplemental electric fan would help alot). ....
To be blunt: that sucks. My 1994 Suburban dual air with the $%@&*#$% R4 compressor here in Arizona (factory R134a refrigerant, too) did way better than that. Now 102F day, still huge difference if Suburban was parked in the sun (so everything like seats, dashboard, etc. is really 150F) or coming from a covered parking spot so all that stuff is "just" 102F. Remember, the air 3 feet over the street on such days is also about 130F, not 102F.
I got vent temperatures in the 40s on ours after only a few minutes, and typically I'd "work" the compressor button on and off to turn off the compressor when it got too cold. I like it cold, would never have kept it if I could only get temperatures like you get.
It never made a ton of sense to me to mix in hot air with the cold, many AC systems just shut off the compressor anyway with an evaporator-mounted switch.
Edited: Mon August 01, 2011 at 8:22 PM by Cussboy
TRB on Mon August 01, 2011 8:31 PM 
GMTech. Is the air flow the same if fan clutch is working correctly. GM product of course gas versa diesel. Reason I ask, I've always seen a warmer temp with diesel motors. Maybe not as much as torque395. Just something that rang a bell when reading this post.
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Contact: ACKits.com
torque395 on Mon August 01, 2011 9:10 PM
Hmm, I thought 20 degrees below ambient was considered normal. Someone on here a while back told me that the AC on the C/K trucks sucked anyways so I thought mine was doing ok. I do feel it needs to be better, but I think part of it is blocked airflow from the condenser. It is a high mileage truck after all. However, the vent temps do need to be cooler. I have a ball valve installed in the heater hose return line, so there should be no hot coolant in the area. I should have installed the valve at the heater inlet, but it was far less convenient to install and use there.
However, I feel it is an airflow issue since it improves while driving but IDK. I'm confused because the fan clutch is working fine. It howls at 200 degrees like it should and the engine rarely gets that hot anyways although it did today with the AC on. The radiator and condenser and other coolers were cleaned up not long ago.
I dont know what else it would be. I just changed a bunch of orings and charged the system so it is full. I also replaced the accumulator, otube, and vacuumed the system.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
torque395 on Mon August 01, 2011 9:15 PM
BTW this truck has an original HT6 compressor. I think it was the first year for the HT6.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
Edited: Mon August 01, 2011 at 9:16 PM by torque395
Cussboy on Mon August 01, 2011 9:31 PM
Post both low and high pressures read at 1500-2000 rpm after holding it there a few minutes. I never had a compressor that long. Are temperatures for the rear air cooler, warmer, or the same?
torque395 on Mon August 01, 2011 9:33 PM
ill get you some pressure readings as soon as i can. Rear temps are the same.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
torque395 on Tue August 02, 2011 1:45 PM
Ok, pressures at 2000 RPM on max AC, with windows open at 100 degrees were 37 psi low, 310psi high. Center vent temp was around 52 degrees.
At 1500 the pressures were slightly different at 40 low 305 high with a center vent temp of about 55.
At idle the pressure was 55 low, 260 high, with a 60 degree center vent temp.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
Cussboy on Tue August 02, 2011 2:17 PM
OK. Now measure again while misting the condenser with water, and/or big electric fan blowing into the condensor.
Also, have you done anything to the AC system recently? When the system was filled, was that done by weight with correct stated level of R134a after the system was fully evacuated?
Edited: Tue August 02, 2011 at 2:19 PM by Cussboy
torque395 on Tue August 02, 2011 5:24 PM
Ok temp is 107 now. At idle before the water the pressures were 65L 260H. At idle AFTER the water the pressures were 45L 140H.
At 2000 rpm after the water, the pressures were 25L 150H and my helper said the vent temp was 56 but it felt colder than that to me. The thermometer might not have had a chance to catch up.
I just worked on the system earlier this week - new otube, accumulator, several orings, vacuumed down for an hour and then filled with five 12oz cans of refrigerant. It might be a hare low and MAY, MAY be leaking ever so slightly but I am not sure. Pressure was maybe a few pounds (maybe 5psi at most) lower today than the other day but temperature variations can cause that although I think it was slightly hotter today when i checked than it was the other day when I filled it.
System holds i believe 4 pounds even with the rear AC. So it might be a few oz low. The big line going to the accumulator was very cold and sweating. The big line going to the rear was cool but not cold and not sweating. If this says anything.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
TRB on Tue August 02, 2011 6:42 PM
Are the 2 lines coming out of the evap the same temp?
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Contact: ACKits.com
torque395 on Tue August 02, 2011 7:07 PM
The small line on the rear evap is very hot the big line is slightly sweating back at the evap but not by the compressor. I cant really feel the small line coming off the front evap because its crammed in by hot engine parts with no room for my hand in there without rubbing against something. I believe i touched it with the tip of my finger tho and it was cool. Perhaps the rear system just didn't get enough when i initially charged the system ? Would 4 oz low be enough to make the small line in the back hot?
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
Dougflas on Tue August 02, 2011 8:31 PM
I'm thinking you are not getting enough heat rejection from the condenser. Make sure the radiator and condenser are back washed...do not bend the fins. Fan clutch fan clutch fan clutch. As old as it is, you're due for a replacement. Water misting confirms poor air flow across condenser.
torque395 on Tue August 02, 2011 9:28 PM
All signs point to clutch fan, BUT, it roars at 200 degrees when the engine starts getting hot. And its moving alot of air at idle, and doesnt freewheel when its off, cold, and spun by hand. All things considered, is it still possible that its not moving enough airflow to keep the ac cool? I am considering an electric fan because I am not sure this clutch fan is acceptable. A new fan clutch for this truck is $200. Ouch!
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
mk378 on Tue August 02, 2011 10:21 PM
You already did the water test and it was conclusive-- the condenser needs more air. Properly working engine fan is much more powerful than electric fan.
JJM on Tue August 02, 2011 10:25 PM
It might seem like it's roaring and moving a lot of airflow, but I bet if you replace it with a new OEM part, then you'll really know what roaring and lots of airflow is.
You might also have too much oil in the system... no mention of flushing. Best bet is to start with a dry system... accumulator and all.
Joe
torque395 on Tue August 02, 2011 10:46 PM
too much oil is what I fear. I blew some oil out of it but didn't do a flush. Then I added a couple oz just to be safe. I didnt blow much oil out of the condenser or evaporator or lines. Accumulator is new.
MK378 - The Lincoln Mark Viii electric fan moves a massive amount of air. I dont know what it compares to a good working clutch fan but I know it can keep a hard working big block cool so surely it could keep my diesel cool? I dont know. The main thing for considering the clutch fan is so that I can turn the fan on with the AC and KNOW that I have airflow. I cant do that with a clutch. Even the auto manufacturers are doing similar things now, even in trucks. Some vehicles even have a computer controlled electric fan clutch nowadays. That would be real nice to have...
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
Cussboy on Wed August 03, 2011 1:11 AM
QuoteOriginally posted by: Dougflas
I'm thinking you are not getting enough heat rejection from the condenser. Make sure the radiator and condenser are back washed...do not bend the fins. Fan clutch fan clutch fan clutch. As old as it is, you're due for a replacement. Water misting confirms poor air flow across condenser.
Quote
Originally posted by: mk378
You already did the water test and it was conclusive-- the condenser needs more air. Properly working engine fan is much more powerful than electric fan.
That's why I asked you to do the misting test. I also think your condenser isn't shedding enough heat. I've found fan clutches to last about 6 years in the Arizona heat.
Edited: Wed August 03, 2011 at 1:12 AM by Cussboy
bohica2xo on Wed August 03, 2011 2:54 AM
Replace the fan clutch. If you really want an electric fan, add the Delco P/N 158686 just like the factory did on certain HD packages. Adding an electric fan to half the condensor in addition to a properly working clutch fan is the way to go. Use a good relay to run the fan when the compressor clutch is engaged.
If you have the 10 blade fan, inspect it carefully while you have it out. A new fan & clutch from the dealer for that vehicle was about 450 bucks last time I checked.
Leave the Lincoln fan in the Lincoln. It was made for a 4.6L engine in a car that weighs less than half what your rig does. Even if your truck was a 4.3L, you don't have the wide open space behind the fan that the Lincoln did.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
torque395 on Wed August 03, 2011 5:48 AM
Well sounds like a new fan clutch it is! Would a Hayden Severe Duty fan clutch be fine rather than an AC Delco from GM? The Hayden is 200, the severe duty one is actually a few dollars cheaper than the regular Hayden clutch. I dont even want to think about what an AC Delco clutch would cost....
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
bohica2xo on Wed August 03, 2011 10:57 AM
The Hayden Severe duty should be fine. The diesels beat the accessory drives pretty hard, so the parts cost more.
The fan affects more than just the A/C. Reduced airflow across the engine compartment kills electronics & plastics.
The electric part number I posted is around 100 bucks. It is a bolt-in, with a bracket on it to span the radiator support.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
torque395 on Wed August 03, 2011 11:22 AM
Yes i looked it up. Its $6o. Where does it go? It looks like it mounts the same way the oil cooler and trans cooler do. So I assume it goes OVER one of those (because theres no room for it otherwise). Does the wiring happen to be there for this too or will I have to wire it up myself? GM did a pretty good job at supplying all the connectors in every truck for different options. It was even prewired for trailer brakes and auxillary power but the PO didnt realize this and wired those in himself.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
bohica2xo on Wed August 03, 2011 12:30 PM
The legs go over one of the coolers, and the fan sits above or below the cooler on that side. it is sort of obvious when you have the radiator support exposed. Been a while since I had to do a new install on one. A quick wald around a parking lot here will probably find one installed - I will look at lunch.
If you have a tow package in that truck, the fan harness may be there as well. It will be missing the relay and whatever else GM could leave off of course. A good wiring diagram will help.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
torque395 on Wed August 03, 2011 2:00 PM
Yes i know it will go over one cooler or the other I just wasnt sure which. This truck has the tow package (i believe the oil and or trans cooler is part of the tow pkg). Its got a 7700# GVWR which is in between a 1500 and a 2500 series truck (part of the diesel package). Plus like mentioned it was pre wired for the trailer brakes and power. I'll dig around for the fan plug, i'm betting its there somewhere. I think I do remember seeing some relays missing somewhere from the fuse box/power center under the hood.
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1996 Chevy Suburban 2500 4x2 6.5L Turbo
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