There's a red plastic electrical connector box about 3"x4"under hood on the right side of the engine right above the power steering unit ??
It has three heavy gg wires in it, and snaps together, like a sandwich, sorta. Two wires are stock battery power feed (in and out of box), and one 8gg wire (out) and leads to the camper power plug in the bed and charges the camper battery. The 8gg wire was installed by the Lance factory when Lance installed my in-bed plug.
Is this red box a stock GMC Sierra item, or did the camper installer put this in??
I'm having some minor electrical problems during wet weather in my truck, not in the camper, and wonder if this box could be getting wet inside and grounding or shorting while it's wet (it's not sealed, just snaps together) ... so am thinking this might be the culprit - most everything else is working properly most of the time - except this intermittant wet weather issue. And when it's dry and I can get under the hood, the power issue's not showing up ... no codes, nothing.
As said , the red box is stock GM , it is also where the heavy gauge wire from the alternator connects . Sticking above it is a ground spike to hook jumper cables to . You haven't said what type of electrical problems you're having . There is a ground wire that bolts to the drivers side front cab mount (under the drivers door) that sometimes gives trouble , try taking the bolt out and cleaning and use some dialectic grease on it .
Okay = good to know ... problems are intermittant gauge readings, and a couple times, no start. Battery was discharging - found one answer, the AC clutch relay was bad and stuck shut, and discharged the battery.
But still getting weird gauge readings - and the 4x4 switch sometimes reads 'neutral' (red dot in center) and sometimes jumps to auto-4x4 without me touching it. I suspect it's mostly still in 2H, but sometimes, I get that sluggish turning in the front-end that you feel when your turning a corner with 4H engaged.
Both issues usually happen when driving in wet weather, or right after wet weather. Once it drys out, no problems. SO, very difficult to diagnose.
Im pretty sure it's moisture getting in somehow, as I've checked just about every thing else. Its so intermittant, it's most often 'not doing it' and when it is doing it, I'm generally driving down the road in wet weather - not very condusive to diagnosing on the side of the road.
As said before, the ground on drivers side at front of door is problematic, especially in wet weather. I didn't see what year your pu is but there was a known problem with the gauge module in some of the early models. I had to have mine replaced when it went totally nuts, the stepper motor on the speedo stopped working properly.
Just retelling my story. My 2003 2500HD GMC ocasionally wouldn't start, battery dead, and although they replaced the battery it was still a problem. I started looking through the TSB's and found one that said there was a switch below the air bag on/off key lock that was intended for a Gumball machine on the cab roof and it was there even if you did not have the Gumball machine and if that switch got pushed, it picked a relay that remained picked drawing power from the battery even after the truck was shut down and would keep doing that until the switch was pressed again. Now the switch has a small LED light in it that comes on and off with the ignition, the relay remains pick and draws down the battery. Of course if you do not have that switch it wouldn't be your problem, it was mine. The document ID is 1712313. Email me with your email address if you want me to email the copy to you.
Good luck
Bob
Seacraft Skipper
"Semper Paratus"
2003 GMC 2500HD 4X4 ExCab L/b Air lift A/B.
2002 Lance Lite 915.
1972 20ft Seacraft Sport Fish.
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