Hopefully this helps some of you Tahoe/Yukon/Escalade and Suburban or even van guys that feel the ac in your rig is subpar. This same stuff can also apply to a single ac but they usually do not struggle as much with only 1 evaporator to pull. I recently rebuilt my AC system on my 97 Express with dual ac and it worked well, but idle cooling just was not as good as I wanted in 100+F temps. I had dual 3,000 cfm electric fans, but they would not keep my 383 and 4L85E as cool as I liked. I switched back to a mechanical fan that did a great job driving around but not so good at idle. Then I decided to add a 16" 3,000 cfm Flexalite fan as a puller between the radiator and clutch fan. While that improved things at idle it was still not quite moving enough air to keep things cold. I cut down a Duramax fan slightly and put it on. Way more airflow at all rpms. I can say it was 102°F this afternoon and 10 minutes after startup with both front and rear blowers on high speed at idle it is cooling 38°F out of the center vents and 40°F out of the left vent, rear is blowing about 40°F and the van felt like an igloo inside.

So starting with the basic ac repair stuff, I flushed the system with ac solvent, blew everything out, I use a disposable spray painters filter/drier on my air compressor to keep the air clean and as dry as possible although Nitrogen would be better, replaced the front orifice tube with a Four Seasons 38902 variable unit, cheap on Rockauto. I put a new replacement parallel flow condenser on it. I also upgraded my 16 year old $180 Valeo replacement compressor for the HT6 belly leaker that I put on years ago after the stock compressor seized with a Sanden 4261. The old compressor had a bit of a rattle in it and since I had it all apart I replaced it even though it was still getting into the 30s at the center vent on the highway. I put 11 oz of SP15 Pag into it, put it all back together and pulled it into a nice long vacuum for over 1 hour to make sure every bit of flush and moisture was out of the system. Then I charged it with ~38oz of R152a (4x10oz cans minus the small amount left in the can as gas at the system pressure and the small amount lost when purging the charging hose, I weighed the cans to determine the amount), system calls for 68oz R134a and 11 oz Pag150 with the stock GM compressor. That put me close to where I want to be. R152a charge is roughly 61% of R134a. With the Duramax fan and the 16" 3,000 cfm PCM controlled puller activated it was running 255 psi and 39 psi with 38°F center vent temps. Shutting off the 16" fan brought the pressures up to 275 and 42 with 45°F center vent temps. The 383 was running 191°F without the puller fan and 185°F with it on, idling at 750 rpm. The van has a March 3-piece underdrive setup that turns the compressor and p/s pump at 25% under drive compared to stock and the fan and water pump at 33% underdrive compared to stock.


New genuine Sanden 4261 I had shipped to me from Sanden in Wylie, TX which is a SD7H15 variant at 9.5 CID per revolution with a 4.41" pulley. With the 6" crank pulley it turns 1.36x crank speed and has a maximum speed rating of 8,000 rpm and a maximum continuous rpm rating of 6,000. I have the PCM set to shut it off at 5,200 rpm or WOT.

The March underdrive pulleys when I test fitted the compressor bracket that I had to grind down to clear the taller aluminum valve covers. I painted that bracket with Duplicolor cast-iron to match the alternator bracket.

 

So I had to break this up.


16" Flexalite 3,000 cfm puller installed behind the radiator with custom mounting brackets.

Swapped the 2006 5.4 Ford fan blade out for the cut-down LBZ Duramax blade. Its on a severe duty Hayden clutch for a 2007 TBSS. It looks extra tight but it has over 1.5" of clearence.

Left vent after idling for 10 minutes with the puller fan activated with HP Tuners. Still need to program parameters to make it come on as an auxiliary as well as stay on for a few minutes after the engine shuts down. I was reassembling the dash after putting the cluster back in. I replaced burned out bulbs in the cluster with red LEDs that are both brighter than the OEM bulbs and do not mess with your night vision as you scan the gauges.

After 10 minutes idling with the 16" puller activated.

This is the center vent, 10 minutes after shutting off the 16" puller fan. Still colder than the R134a stock system ever though about being. I think it ran about 56°F at idle in this heat when it was NEW!

AC Pressures after idling 10 minutes with the electric puller fan off.

This is the Sanden SD7H15 performance chart. At my ~2,100 rpm cruising speed with the 1.36:1 overdrive will be turning ~2,850 rpm and delivering more than 2x the BTU output. Going off memory, I think the lowest I have been able to adjust the cycling switch before the evaporator freezes is around 29°F out the vents. At 38°F at idle, have no doubt it will be in the low 30s going down the road.

Will also add that it cost me less than $20 to fill the system up. The density of R152a is 61% of R134a. That puts the theoretical charge at 41 oz. Mine is cooling well and returning superheat to the compressor at only 38 oz.

https://www.samsclub.com/p/dust-off-...ns/prod9540095

 

I previously had the full size duramax fan on a clearenced factory 97 shroud, but the stock air cleaner boxes have a habit of breaking apart on the 96-2000 vans. So I swapped to an 01-02 fan shroud and Donaldson designed air filter housing with a custom 4" air intake and 100mm MAF. The Duramax blade had to be trimmed from ~21" to 19" to clear the shroud. The air box nearly completely hides the engine and when the mile long oil fill tubes and dipsticks as well as the coolant bottle is in place it looks nearly stock

I will also say even with the hood open, these vans heat soak the air intake. After 20 minutes of running stationary my IATs were over 150°F.

 

Hey man, great job with this project, do you mind contacting me on my cell, I have some questions for you sir. my name is David, 8172919302.