What did you do to your NBS GMT800 Tahoe/Yukon Today?

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mattbta

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I tried my hand at fine tuning the A/C charge now that temps have approached 90 degrees here in Texas. I can't seem to figure out the best way to gauge how much refrigerant I should add (I know, I should be measuring by weight but we're long past that unless I want to evacuate, vaccum, and recharge from scratch which I'd like to avoid). Should the fan be blowing on high, or on low when I'm reading pressures? Should I have a shop fan blowing across the condenser, or spraying with a hose, or leave it completely alone and let the vehicle pull air across it, unassisted?

I can't seem to get it much colder than 50 degrees from the vent with ambient temps around 75 and humidity around 70%. I think the old girl is capable of better cooling, but maybe based on her age it's time for a new condenser since I'm sure after a quarter million miles, the OEM is likely not as efficient as it used to be.
Curious to see where you get. Mine had both ports replaced (within a week of each other) last summer which required evac/vac/refill 2x. I'm skeptical because prior to this, it would push 40* all the time. Now it barely breaks 50* after sitting in the sun and driving 20 min or so. I brought it back to the shop and they inspected and didn't observe a leak but I wanted to know the levels. They wanted to charge me a service fee to evac and refill again but I declined as it may need further work later.

Do you have gauges for checking pressure? Might need to drop by once we get more info on the "how". :D.
 

clandr1

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Curious to see where you get. Mine had both ports replaced (within a week of each other) last summer which required evac/vac/refill 2x. I'm skeptical because prior to this, it would push 40* all the time. Now it barely breaks 50* after sitting in the sun and driving 20 min or so. I brought it back to the shop and they inspected and didn't observe a leak but I wanted to know the levels. They wanted to charge me a service fee to evac and refill again but I declined as it may need further work later.

Do you have gauges for checking pressure? Might need to drop by once we get more info on the "how". :D.
Haha, yep - bought these back in 2015. Will be happy to share lessons learned if/when I figure this out.

MOUNTAIN 8205 R-134a Brass Manifold Gauge Set with Couplers https://a.co/d/87JBRRm
 

Sam Harris

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Haha, yep - bought these back in 2015. Will be happy to share lessons learned if/when I figure this out.

MOUNTAIN 8205 R-134a Brass Manifold Gauge Set with Couplers https://a.co/d/87JBRRm
Swiped up.. thanks for helping me spend money. :cool:

I’ll have to use my thermometer later, to see what kind of temps I’m getting, for comparison.
 

Sam Harris

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Just picked up the kiddo from school.
Ambient Temperature: 78°
Relative Humidity: 70%

I read between 49 starting the drive from a parked idle (in garage), to a low while cruising of 40.6, but wasn’t able to get a picture while driving. Lol
Around 41-43 while idling at a stoplight:

I wish my home A/C worked that well! It’s around 49 at about a mid-house vent.
 

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mattbta

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Just picked up the kiddo from school.
Ambient Temperature: 78°
Relative Humidity: 70%

I read between 49 starting the drive from a parked idle (in garage), to a low while cruising of 40.6, but wasn’t able to get a picture while driving. Lol
Around 41-43 while idling at a stoplight:

I wish my home A/C worked that well! It’s around 49 at about a mid-house vent.
I haven't used my IR, yet. The shop did and claimed 38* but I didn't see it. I have one of those old man thermometers stuffed in the vent. THIS PIC IS BEFORE MY LEAK/VALVE REPLACEMENT. Best I've seen lately is 42* but that's after pulling out of the garage. Usually around 50*
IMG_0220.jpeg
 

Sam Harris

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I haven't used my IR, yet. The shop did and claimed 38* but I didn't see it. I have one of those old man thermometers stuffed in the vent. THIS PIC IS BEFORE MY LEAK/VALVE REPLACEMENT. Best I've seen lately is 42* but that's after pulling out of the garage. Usually around 50*
View attachment 399489
Lol. I’ve got several of those, and initially, looking at my home temps, I was using my ThermPro, which is super accurate. But I got lazy, standing there with my arm in the air.. so decided to go with the IR.
 

Sam Harris

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I haven't used my IR, yet. The shop did and claimed 38* but I didn't see it. I have one of those old man thermometers stuffed in the vent. THIS PIC IS BEFORE MY LEAK/VALVE REPLACEMENT. Best I've seen lately is 42* but that's after pulling out of the garage. Usually around 50*
View attachment 399489
Brrr!! Damn, that’s frosty!

IMG_9131.jpeg
 

ncalvo

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Brought my ac low side pressure up to 55# while it was 88deg outside and she's blowing ice cold again I am happy. My leak test was good to go last time I did major work on the system but it seems I still have to add half a can to a full can of 134 yearly.
 

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