When im at a red light i turn on my ac and my engine gos off . but i can run my ac when im on the highway or im moving in the car. but when im getting ready to come to a stop i have to turn off the ac or the 2005 chev, trailblazer will shout down then i have to start it back up.

Check engine light on?

Are you RECIRCULATING?

The common element to me is the battery - bad voltage can upset the computer.

check the freon charge if it is low the system shuts down

Does the engines electric cooling fan turn on when it gets hot? Does it cool off if you turn the AC on?

they either did not put new fans on or they did not connect them correclty its all in the fans the fans cool the water for the engine when it cycles through the engine it cools off there at the radiator and it takes longer to heat up cause allways in any car when you turn on the ac it will turn high or secondary speed on fan so it cools the water even more so check fan if they replaced it motor might be bad or again check connections

It sounds like a bad thermostat, but you could have excessive air in the system also. Thier is an air bleed screw on the thermostat housing that is used for bleeding the system. I would also check your cooling fans, to do this easily turn your ac on max setting and check to see if the fans are spinning. when the ac is on max the fans should be spinning all the time.

hey im having the same problem for the most part....and i would try turing on the lights and the AC basically anything electric...if it gets worse or dies than i would say its your alternator. good luck

turn on ac and see if fans come on ,,see if fans or fan kicks into high after a little while ,look for reason why fans or fans do not run with ac on they have to run ,relay? or high side switch check preasures on ac ,low side and high,high side may be to high for fans or fan to cool down ,,ac problem or to much freon,,,radiator new?

I would try a waterpump.