I attempted this mod this morning and here's what I found out.
Before: Both defrost buttons (full defrost and defrost/floor mix) would automatically engage the A/C without turning on the A/C light. Pressing the A/C button at this point would turn the light on and off, but I was not able to disengage the A/C while in defrost mode.
After: Selecting one of the defrost functions would still automatically engage the A/C. However, now the A/C light would come on as well when defrost was selected. Pressing the A/C button at this point would turn the light on and off AND successfully disengage the A/C.
So this does indeed work. The only problem I had was returning the system back to factory specs. I went through the same procedure several times but was unable to do so. Dave424, can you double check this? Thanks.
