Duramax Diesels Forum Truck of the Week
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Old 05-17-2018, 09:16 PM
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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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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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Old 05-28-2018, 02:16 PM
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Originally Posted by DAVe3283 View Post
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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I timed it to be cycling every 7 seconds, I can see the leak visibly itís bubbling with the truck off, I went to the dealer and ordered the full replacement hose


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Old 05-28-2018, 05:49 PM
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Originally Posted by MidnightLB7 View Post
I timed it to be cycling every 7 seconds, I can see the leak visibly itís bubbling with the truck off, I went to the dealer and ordered the full replacement hose


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While your replacing the hose go ahead and do yourself a favor and change the orfice tube and accumulator
Make sure to put a vacuum pump on it for at least 30 minuets and let sit for 30 to check for leaks before recharging
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Old 05-28-2018, 06:09 PM
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While your replacing the hose go ahead and do yourself a favor and change the orfice tube and accumulator

Make sure to put a vacuum pump on it for at least 30 minuets and let sit for 30 to check for leaks before recharging


Parts guy at the dealership showed me what all is included, I donít know much about AC units but orifice tube is included with the hose purchase, which part is the accumulator?





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Old 05-28-2018, 06:55 PM
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That's the liquid line that's leaking, and a new one does come with a new orifice tube. The accumulator is the large silver canister hooked to the firewall, sometimes called a receiver or drier.

If you still have refrigerant in the system, you don't technically need to replace it, but with what all is coming out of your leak, I'd wonder how clean the system is, and replace the accumulator if it was me. They are cheap on amazon.com or in local parts stores.

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Old 05-28-2018, 07:00 PM
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You probably just need an oring. Did you try tightening it?
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Old 05-30-2018, 06:58 PM
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Originally Posted by Chevy1925 View Post
You probably just need an oring. Did you try tightening it?


Quote:
Originally Posted by DAVe3283 View Post
That's the liquid line that's leaking, and a new one does come with a new orifice tube. The accumulator is the large silver canister hooked to the firewall, sometimes called a receiver or drier.

If you still have refrigerant in the system, you don't technically need to replace it, but with what all is coming out of your leak, I'd wonder how clean the system is, and replace the accumulator if it was me. They are cheap on amazon.com or in local parts stores.

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I did try tightening it, the leak is coming out of the side that doesnít tighten up, figured Iíd just replace it all, since Iíll be in there working on it Iíll look into the accumulator for replacement aswell


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Old 06-05-2018, 08:15 AM
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That connection is where your orifice tube is. You probably just need a new oring, replace the orifice while it was apart, and put anew accumulator in it while you're there. Add 2 ounces of oil for a new accumulator, an extra ounce for the line, evac, and recharge.
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Old 06-05-2018, 08:20 AM
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That connection is where your orifice tube is. You probably just need a new oring, replace the orifice while it was apart, and put anew accumulator in it while you're there. Add 2 ounces of oil for a new accumulator, an extra ounce for the line, evac, and recharge.
It sounds like he had already bought a new liquid line. If so, might as well just throw that on there and not worry about it.

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