a/c works moving, not so good when stopped

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  #1  
Old 07-15-10, 01:13 PM
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a/c works moving, not so good when stopped

Hi, New here... Got a 99 suburban 2500 4x2 diesal, front and rear ac, great truck! The a/c cools very well when driving. But when in stop and go the temp goes up to 70 degrees with MAX ac mode.(out side temp 90+) Had serviced in the spring. not sure what was done.

There isn't a sight glass to see if the bubble.

Any suggestions, thanks!
 
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Old 07-15-10, 09:27 PM
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If you have an electric fan or fans for the "condenser"/radiator, check to be sure that is working. Could be blown fuse or other problem.

The A/C "condenser" is the set of coils in front of the radiator. This needs to have air blowing over it for the A/C to cool properly.

So I suspect the fan(s) is not working... So when you are driving air is blowing over the coils, but when stopped no air is blowing over the coils.

I don't know about your specific vehicle, but there are all sorts of different fan arrangements. Some are just a mechanical fan attached to the engine and this has a "clutch" which can go bad. When warm it should be difficult to turn the fan with your hand after the engine is stopped.

Other vehicles might have two electric fans. One for cooling the radiator and another for the A/C only. If the A/C is off, only one fan might run, but only when the engine gets hot. A/C on maybe both fans run. Or maybe just one fan will run when A/C on and engine not too warm.

You would need to consult a factory service manual to see which fans run at which times. How it *should* work...

A test to see if this is the problem... Park vehicle in driveway and aim a house fan at the front of the vehicle. See if it cools better inside the vehicle.
 
  #3  
Old 07-18-10, 03:13 PM
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well, truly, you have massive cooling airflow moving, and none of that waiting at the red light.

a/c compressor on those (i have 2000 silverado) is belt driven. 1st thing to do is to check if it's not loose. belt, i mean. prolly simplest and obvious cause.

cuz it's belt driven, engine rpms go up(driving) - more power sent to a/c compressor; engine goes down to idle, which should be around 550 rpms, less power to a/c.

you have separate a/c belt, right?

freon pressure can be easily checked by any a/c shop free of charge. also, locate hot and cold lines on a/c and touch them with hand. keep in mind, hot line can be just that - HOT. is the cold line cold-cold? or warmish?
 
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