Duramax Diesels Forum Truck of the Week
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Old 05-17-2018, 09:16 PM
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MidnightLB7 MidnightLB7 is offline
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Default 2003 LB7 duramax AC causing idle surge

Figured out my truck only surges at idle when my AC is on, every couple of seconds it idles up slightly consistently, one of my AC lines is leaking and wet around one of the fittings by the refrigerant container

When the AC is off truck idles perfectly, hit the AC button surging starts, hit off and it stops again

Has anyone else experienced this? Iím thinking my compressor is going or is causing too much draw on the engine causing the surge, opinions on where to start or go from here?


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Old 05-17-2018, 10:56 PM
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DAVe3283 DAVe3283 is offline
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If the A/C charge is low (from leaking out), the compressor will cycle rapidly at idle. This could feel / sound like a surge.

Pop the hood and watch how quickly the compressor cycles on & off. It should stay on for at least 30 seconds, ideally much longer. If it is turning on & off more rapidly than that, that's probably your "surge".

On both of my LB7s I can tell when the compressor turns on and off. The idle does glitch slightly then recover. On the truck, that's once a minute or two at idle. The Suburban has an expansion valve so it turns on and stays on, but I can still tell the initial hit.

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