Better AC with different size pulley?

[GoToGuy]

Unless you do upgraded compressor, the rated compressor is not as effective as idle. It performs best, most efficient, effective above 1500 rpm. It moving more refrigerant for heat transfer. Are you using the recirculating setting. Controlling cabin air, not trying to cool outside air flowing in. Did you check the charts for where your system should be at in normal working condition?

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[L31MaxExpress]

The compressor is new, but i'm not sure of the brand. I know it's not a Sanden. I would hate to buy another new one just for the pulley. Do you know the size difference between the two compressor pulleys? And can i just pull a pulley off an express van and install on mine?

4.25" vs 5" if memory serves me correctly. With the IIRC 8.25" crank pulley it amounts to a fair bit higher compressor speed.

 

[L31MaxExpress]

Unless you do upgraded compressor, the rated compressor is not as effective as idle. It performs best, most efficient, effective above 1500 rpm. It moving more refrigerant for heat transfer. Are you using the recirculating setting. Controlling cabin air, not trying to cool outside air flowing in. Did you check the charts for where your system should be at in normal working condition?

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I have not seen that chart. This is the one I have in both my Vortec era Express and Tahoe FSMs.

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[GoToGuy]

It out of the 95 service.

 

[GoToGuy]

So.. 8.25 ÷ 4.25 = 1.9 ratio
And idle is 750 rpm × 1.9 = 1455 compressor pulley speed.
So cruise 1950 rpm × 1.9 = 3783 " "
Alternator pulley must be smoking fast at 4500 shift.

 

[JohnZ71]

is swapping the pulleys easy? Do they just unbolt? I haven't studied it enough to find out.

 

[L31MaxExpress]

So.. 8.25 ÷ 4.25 = 1.9 ratio
And idle is 750 rpm × 1.9 = 1455 compressor pulley speed.
So cruise 1950 rpm × 1.9 = 3783 " "
Alternator pulley must be smoking fast at 4500 shift.

5,500 rpm shift here.

 

[JohnZ71]

I snapped a picture of my compressor, are you able to tell if it’s the bigger or smaller pulley? It’s UAC brand part# CO20151C. When I googled it, the site said it was 5 piston/10 cylinder?

 

[L31MaxExpress]

I snapped a picture of my compressor, are you able to tell if it’s the bigger or smaller pulley? It’s UAC brand part# CO20151C. When I googled it, the site said it was 5 piston/10 cylinder?

That is the larger pulley. The belt rides in a recess behind the clutch face of the pulley on the smaller pulley.

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[1998_K1500_Sub]

I would also investigate whether there's undesired airflow:

- The seal b/t the front air handler and the cowl (pictured) is notorious for leaks; it leaks on my Suburban, which is very evident in the wintertime b/c it allows a cold draft of air to enter behind the glovebox into the cabin. Certainly in the summer it provides a path for warm outside air.

- The seals b/t the dampers within the air handler may not be routing the air completely though the evaporator / around the heater core

Others will hopefully comment.

@east302 has posted often about air handler issues / rebuilds, as have others.

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(this picture is courtesy of someone else; I pirated it years ago, possibly from someone on GMT400)