AC Trial and Error

95 Tahoe said:

The stock switch I'm using cycles off at 26 PSI. How do you keep your evaporator from freezing at 22 PSI, that is like 25 degrees?

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L31MaxExpress said:

Cannot charge off pressures alone, need superheat and subcooling readings. I try to run 6-9F of superheat at the accumulator outlet. I recently added 8-10 oz of refrigerant to the 1987s system and saw less than 10 psi change in pressure but the superheat went from ~15F down to 5-6F and it cools noticeably better. If your accumulator outlet is not ice cold, the system is low on refrigerant. My accumulator actually starts to pickup frost on the exposed aluminum before the cycling switch cuts the compressor.

Tested in 103F and 35% RH, mine was holding 35/235 with the pusher condenser fan off. With the condenser fan on it dropped to 30/215. At 1,500 rpm it was 25/230. At 2,000 rpm the low side dropped a bit more. Cutout is happening at about 18-19 psi.

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95 Tahoe said:

The return at the accumulator is around 35-40 degrees. I add a little at a time until I get the lowest temp and stop. I have a slow leak so it's never really perfect. Our relative humidity has been close to 70% the last several days.

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isomswim said:

So update. I said screw it and got a 88947 compressor. It was hot outside that day but filled with 36oz of R152, math comes out to 60% roughly of the charge. So far in the TX heat and even traffic I hardly break a sweat. It's comfortable temp, need to get dash fully back together for measurements. I had originally replaced the Condenser with a 4712 condenser from Amazon, but measurements are all over the place when researching them, as some sites also have it as Serpentine when it's not. I know it's not the narrow condenser but that's the only thing else I'd change at this point.

Aux fan I have is the OEM style but I have the Passenger side mounted oil/trans cooler so I gotta mount it Drivers side with some work.

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L31MaxExpress said:

My brothers 99 Suburban had holes on both sides of the core support. It had the transmission cooler. It also had the condenser fan mounting holes, was pre-wired for the fan and had the fan enabled in the tune. I almost feel like someone removed it earlier in its life. I put a relay in the fuse block, bolted up the fan, plugged the harness into it and it worked. I have seen other trucks and SUVs setup the same way and I have seen others with no provision at all. The cavities in the fuse block for the relay are not wired and the PCM does not have the fan enabled in the tune. Become kind of a mystery to me why some were setup for the fan but no longer had one if they ever did. I have seen the OEM pusher fan installed on both sides of the vehicle as well. Some on the LH hand side and others on the RH. Seemignly no reason for that either. I have seen the transmission on both sides as well. Both were the same year, same model and same engine in this case. One also had a serpentine condenser and the other a parallel flow.

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L31MaxExpress said:

My brothers 99 Suburban had holes on both sides of the core support.

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1998_K1500_Sub said:

So a person could install two of the aux fans if they wanted, provided:

- there's room on both sides (e.g., my Suburban has neither the trans nor engine cooler, so it could be done; the mounting holes are present)

- there's adequate margin in the alternator / wiring / relay(s) to accommodate the additional current draw; a second relay may be required.

I know I've measured the current drawn by the aux fan on my Suburban but I can't remember the number

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