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Strange electrical issue

I replaced my car battery recently. Now, when I turn on my defroster or air conditioning, the engine stalls out. Scanning tool shows no codes, pulleys o.k. please help!

This thread on another forum should help.

Not knowing the year or miles on the Trailblazer, I’m assuming it has some miles on it. The jist of the thread is that over time the throttle body gets dirty, the computer compensates for this to keep the truck running normally. When the battery is disconnected for more than 30 minutes the computer settings are lost. When the truck is restarted the default settings are not enough to keep the engine running when the ac is turned on.

Try cleaning the throttle body with throttle body safe cleaner and an old toothbrush. Do not use carb. cleaner as it will damage the coatings on the throttle body and the MAF sensor.

Ed B.

I suspect your alternator is dying, especially if it had to work overtime when the previous battery was on its last legs. A charging system test would be a good idea here.