defrost/ac affecting vgt

PSD-stroker

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Hey
I recently got the ultimate x tune from ID, I was having idling issues (vane sweep) so I got a couple of revisions. The last one they tested on their truck and confirmed that it was good, it still had the same issue for me. I was checking a few things and reflashed back to the first tune they sent, while doing so I shut off the heater, lights, radio all that, started the truck up and all was good, drive it around and everything is good. Once I got back home I let it idle for a few minutes as the problem was more pronounced at temp, all was good until I turned the defrost on, this caused the vgt duty cycle to go from 29% to 80% constantly, turning the ac on would cause the turbo vanes to sweep.

Basically my question is what would cause this? wiring? vacuum? ecm? could this be a tune issue still? None of my other tunes from them do this, I plan to get ahold of them with this issue, maybe they have some insight but I figured I would come here as well. Thanks in advance!
 

6.0 Tech

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Is your battery voltage good? Maybe your alternator is dying, and having the compressor on pulls voltage down enough to cause issues. Or maybe the compressor is starting to lock up, and the motor is trying to compensate for the rpm drop by upping the load and whatnot to keep it running.
 

PSD-stroker

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Battery voltage is between 13.7 - 14 volts. How would that relate to the vgt though? Just causing a higher draw and intern allowing a drop in voltage going to the turbo or would it be to the ecm? I should add that I could only get this to happen when the truck is at temp.
 

6.0 Tech

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i dunno if it would relate, but if the computer sees low voltage, it starts screwing with all sorts of chit. It was just a random ass thought, and something easy to check.
 

PSD-stroker

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Anyone have a wiring diagram? Is duty cycle controlled by voltage, if so does anyone know the voltage to duty cycle relation?
 

Zmann

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Unhook the compressor and try it again?? but it's not a vacuum deal by any means

the VGT uses voltage via a PWM signal so it's not easy to throw a meter on and verify
 

PSD-stroker

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So I unplugged the ac condenser and took it for a drive to get it up to temp, now it idles like its supposed to at temp regardless of what I do with the climate control. I'm still getting a whistle at idle until its up to temp though which is weird. Will be unplugging the compressor and trying it once it cools down a bit.
 
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79jasper

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How did you unplug the condenser? That's "basically" just a radiator.
You likely unplugged the low pressure cut out/cycling switch. Which in theory, should kill the compressor.

Sent from my SM-G892A using Tapatalk
 

PSD-stroker

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Sorry it was the accumulator that I unplugged. I pulled the fuse and relay for the compressor and there was no difference aside from just having the accumulator unplugged.
 

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