I had to replace a leaking high side valve, so I figured I would post some pressures and temps on a good running ac in a tahoe with front and rear. It may help someone to figure out what is wrong with theirs by comparing.
After putting in 44 ounces (2 lbs 12 ounces like it says) in it, I know the charge is correct.
The ambient temp was 96 degrees in the shade, truck in the shade.
Truck is a 99 Tahoe 128,000 miles with front and rear AC manual controls.
I had cleaned the radiator and condenser a few weeks ago (tons of crap blown out of it)
All readings are in park at idle with the hood open (hood closed may have higher high side readings due to poorer air flow).
I ran the AC for at least 30 minutes till the inside of the truck was about 64F by the recirc air inlet. AC run on recirculate for all tests!!
I did readings with just the truck stock, and with a portable evap cooler in from of it.
Low speed blower stock cooling:
34F......23 psi low.....235 psi high
Low speed blower with evap cooler:
33F.....24 psi low.....190 psi high
High speed blower stock cooling:
42F.....33 psi low....260 psi high
High speed blower with evap cooler:
38F.....28 psi low....205 psi high
4 degree vent difference just at idle with better airflow!
Front and rear AC on toghether measured at front vents:
Low speed blower stock cooling:
40F.....31 psi low.....245 psi high
Low speed blower with evap cooler:
35F.....23 psi low.....175 psi high (cut out at 22psi with evap @1800 rpm)
High speed blower stock cooling:
52F....46 psi low....280 psi high
High speed blower with evap cooler:
44F....34 psi low....195 psi high
8 degree vent difference with better cooling at idle !!!!!!!!!
Evap cooler was about 75F in front of radiator.
Freeway test at 70 mph @ 2000 rpms 3.73 gears:
Truck internal ambient at blower motor 59F
Outside 95 F.
Front only on high cycled continually at 39.6F
Front and rear on high cycled continually at 36.4F
My final verdict is that the stock fan sucks....or has lack of suck. You can see a major difference at idle with or without the extra cooling. Efans are in my future for sure like I had on my 93. Huge difference between idle and the freeway (of course).
Also, it cycles way too much when the inside is nice and cold. I plan to get a few psi lower cycling switch....the higher the rpm the worse it is.
I noticed when the ac has been on for a bit, it blows the coldest temps when both front and rear are on high.
Another thing I was thinking......the lower the high side pressure, the less power it takes to turn it. So better airflow at idle could save some fuel.
After putting in 44 ounces (2 lbs 12 ounces like it says) in it, I know the charge is correct.
The ambient temp was 96 degrees in the shade, truck in the shade.
Truck is a 99 Tahoe 128,000 miles with front and rear AC manual controls.
I had cleaned the radiator and condenser a few weeks ago (tons of crap blown out of it)
All readings are in park at idle with the hood open (hood closed may have higher high side readings due to poorer air flow).
I ran the AC for at least 30 minutes till the inside of the truck was about 64F by the recirc air inlet. AC run on recirculate for all tests!!
I did readings with just the truck stock, and with a portable evap cooler in from of it.
Low speed blower stock cooling:
34F......23 psi low.....235 psi high
Low speed blower with evap cooler:
33F.....24 psi low.....190 psi high
High speed blower stock cooling:
42F.....33 psi low....260 psi high
High speed blower with evap cooler:
38F.....28 psi low....205 psi high
4 degree vent difference just at idle with better airflow!
Front and rear AC on toghether measured at front vents:
Low speed blower stock cooling:
40F.....31 psi low.....245 psi high
Low speed blower with evap cooler:
35F.....23 psi low.....175 psi high (cut out at 22psi with evap @1800 rpm)
High speed blower stock cooling:
52F....46 psi low....280 psi high
High speed blower with evap cooler:
44F....34 psi low....195 psi high
8 degree vent difference with better cooling at idle !!!!!!!!!
Evap cooler was about 75F in front of radiator.
Freeway test at 70 mph @ 2000 rpms 3.73 gears:
Truck internal ambient at blower motor 59F
Outside 95 F.
Front only on high cycled continually at 39.6F
Front and rear on high cycled continually at 36.4F
My final verdict is that the stock fan sucks....or has lack of suck. You can see a major difference at idle with or without the extra cooling. Efans are in my future for sure like I had on my 93. Huge difference between idle and the freeway (of course).
Also, it cycles way too much when the inside is nice and cold. I plan to get a few psi lower cycling switch....the higher the rpm the worse it is.
I noticed when the ac has been on for a bit, it blows the coldest temps when both front and rear are on high.
Another thing I was thinking......the lower the high side pressure, the less power it takes to turn it. So better airflow at idle could save some fuel.
