1BadAction

iTrader: (10)

ok, as far as I can find, there are 5 different pins in the ECM red plug(99 silverado) that relate to the a/c.

11 Recirc Sw DK BLU (to 2 pin connector on passenger side of harness) (A/C high press)

17 AC REQUEST DK GRN/WHT

33 Recirc Door DK GRN

43 A/C CLU DK GRN/WHT

55 CYC SW in DK GRN (A/C system)

I'm pretty sure 11 and 43 go to the compressor, and 17 and 55 go to the A/C head unit, that leaves 33. what is it for? are my locations right? any guidance is appreciated. thanks.

bczee

iTrader: (12)

In the HAVC box under the dash.. In general, there is a few doors to direct the air (heated or cooled) to the correct outs, there is also a door to either let the air in from the outside vent or to be recirculated from the inside air (some call this setting MAX). The PCM or BCM can control this or some old cars have manual controls that would operate the doors by vacuum or elecrical control on the door.

1BadAction

iTrader: (10)

ok... I didnt know that the PCM actually had "control" of the recirculation in the newer vehicles. In my 93 the electronic control handles that.

bczee

iTrader: (12)

As I said, I was not sure if the PCM or BCM did. I am sure someone else would know for sure.. I am using my stock OEM Chevelle HVAC and controls.. so I didn't research that far into the pin and other harness cause I didn't need too.