I think you are confusing the recirculation fans with the Equipment cooling fans ! Fred.

no i know what those do that pulls the heat generating from all the avionics the recirc fans pull air pulls air from the cabin and recycles it in the forward cargo bay. thats what they do.It reduces laod on the packs. Why? well because the packs must draw air to condition, cool and or warm the air thats flowing into the cabin. Instead of constantly doing this through out the whole flight. the recirc fans recycles the cabin air so the packs does not have to constantly provide fresh air to the cabin this extends the life of the PACKS.the fans pull the air through a valve in the aft cabin and brings it forward to the fwd cargo bay where it's re-conditioned before being cycled into the mix manifold to start it's journey back to the cabin for passanger comfort..If i'm wrong Jack_C will correct me

To all of you with temp issues, you shouldn't be leaving the APU on for bleed air through the packs on the ground, if at all possible. It's best to shut the packs off, turn the APU off, and then use ground air. The APU powers the packs with bleed, but the packs just mix ambient air with hot air to get the end result of conditioned air. At altitude, this works perfectly. On the ground, pulling in the summer's hot air, it's not working so well. Then again, my understanding of how packs work is very simplistic, so that may not be spot on.

I start my apu just before pushback, for engine start-up mainly. The temperature problem appears even at FL200+. Just a little spin of the temperature control to the left will get the duct temperature from 60+ to around 20 in about one minute.

no i know what those do that pulls the heat generating from all the avionics the recirc fans pull air pulls air from the cabin and recycles it in the forward cargo bay. thats what they do.It reduces laod on the packs. Why? well because the packs must draw air to condition, cool and or warm the air thats flowing into the cabin. Instead of constantly doing this through out the whole flight. the recirc fans recycles the cabin air so the packs does not have to constantly provide fresh air to the cabin this extends the life of the PACKS.the fans pull the air through a valve in the aft cabin and brings it forward to the fwd cargo bay where it's re-conditioned before being cycled into the mix manifold to start it's journey back to the cabin for passanger comfort..If i'm wrong Jack_C will correct me

sorry for my bad grammer i can't edit my post for some reason

I start my apu just before pushback, for engine start-up mainly. The temperature problem appears even at FL200+. Just a little spin of the temperature control to the left will get the duct temperature from 60+ to around 20 in about one minute.

I observed the same behaviour on my last three flights. Why does the cabin and duct heat up, if you have the temperature selector in auto with an outside temperature of 30° or more? I always had to "manually" set it down to cool and everything was back to normal in a matter of seconds. Doesn't make much sense to me, that the auto setting is heating up the whole air conditioning system instead of cooling it down. Can someone explain this behaviour to me, or is it maybe a little bug?

does the aircon car provide air conditioning? I tunred off my apu on my ngx and the duct pressure went off