Why does AC fan go to "high-high"?

spikefish · August 1, 2004

I have a 2000 Sierra. No complaints.

Question?

When I run my AC on high, occasionally the fan goes to "high-high", for no apparent reason. It is obviously putting out more air volume for no reason, and randomly.

Would like to be able to request such a speed on occasion.

titanium10k · August 2, 2004

my guess would be that you are running your ac on the outside air function, which when moving slowly the air isnt as fast as the recirculate mode. On these trucks Im pretty sure if it is hot out and the ac is under heavy load or temp and your not moving very fast it swaps over to recirculate mode to cool the air better and on that mode the air will blow faster than the other mode.....hope that helps, this info i believe is in the owners manual also

spikefish · August 2, 2004

Titanium,

Darn if your analysis hits the nail on the head! Happens only when in extreme traffic or at a stop. I looked in the manual but didn't see the issue, not surprisingly as the manual is 50% child seat info! Nothing against kids, I guess GMC has to cover their bases.

Thanks a lot,

Walter