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So my 2003 Chevy Trailblazer dies when I have the AC running. When I'm idling mostly (at a red light or stop sign) and it's died a couple times while driving at a low speed (thru a parking lot).

Something is also preventing it from being read properly on a diagnostic machine. Seems like no one can tell me what's wrong with my car.

Why does my truck die when I have the ac running?

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    Welcome to the site. Can you tell us which engine/drive train is in your trailblazer? Does the A/C blow cold when the engine is running? Is the check engine light actually one while the engine is running? You said you're not able to read the diagnostics properly, could you explain what is actually going on? Does the scanner actually communicate and is not getting back codes? or does the scanner throw an error and not even communicate? Have you tried different scanners? Has any work been done to the vehicle lately? If so, what? – Pᴀᴜʟsᴛᴇʀ2 Jul 27 '17 at 14:14
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So the Air Conditioning system can place a pretty large load on the engine. If the load is too large, the engine will stall at idle. If the engine is weaker than normal, the engine will stall at idle.

Large A/C load caused by:

  • Driving in really hot location (Phoenix, Las Vegas, etc...)
  • Driving in hot high humidity weather (Generally in the southern USA)
  • Poor airflow thru radiator and condenser (fans in working order? all seals in place? Nothing blocking the inlet to the radiator?)
  • Somebody has replaced parts and you have different drive ratio on the A/C compressor.

Poor engine power caused by:

  • dirty fuel filter
  • plugged air filter
  • possible vacuum leak caused by old cracked rubber hoses on top of engine?
  • poor spark (possible ground on spark plug wires? inoperative spark plug)
  • worn engine (generally worn piston rings or valves. Have you recently tested the compression on each cylinder?) How many miles do you have on this vehicle? How many miles do you expect to get out of this vehicle? My suspicion is anything over 180,000 miles will not be putting out full power on that vehicle, without an engine rebuild.
  • most other engine power issues will generally set a check engine light, indicating an OnBoard Diagnostic (OBD2) trouble code.
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