High Resistance in battery Cables

[djlightning]

I have a slow crank on my 2018 GMC Sierra even with a new battery. The car is under a bumper to bumper warranty so I took it to the dealer. They say that I  need to replace both the negative and positive battery cables due to high resistance. They state that the spec for voltage drop is less than 100mV for either cable and their testing showed a drop of 460mV on the negative cable and 260mV on the positive cable. Has anyone seen something like this before? Cables are not covered unde my warranty and parts and labor are $832. Just based on my experiece with IT cables it usually is a termination/corrosion issue and not the cable itself, let alone both cables at the same time. Maybe it is something else too. Regardless I wanted to seek opinions here before I plunk down the cash on the reapair. Thank in advance for any support.

[Jsdirt]

The spec used to be 500mV for battery cables. I'm betting on all the electronics aren't playing well with that spec these days so they've lowered it to 100mV. Add in some low-bidder copper wiring and you've got a very common failure.

 

If they're not going to cover it, get it the hell out of the dealer. I'd suggest doing it yourself over a weekend.

 

If that's not an option, ANY private garage can handle this, and I'd wager it'll save you 75% of that quote at a MINIMUM. Most garages can make their own cables so you won't have to pay $300 (just a guess) for OE ones, AND it'll be better quality cable!

 

I wouldn't use OE anyway, since they can't even get them to last 10 years today. 

Edited February 4 by Jsdirt

[txab]

There have been plenty of posts over the years of battery cables failing internally, out of site. Termination points aren't always the problem

[carkhz316]

If they did indeed voltage drop the entirety of the positive side and the ground side, it honestly doesn't sound excessive. On paper it does, but you have hundreds of amps of current and half a dozen connection points. All that I've measured on healthy trucks have been anywhere from 400mV to 800mV total. I'm betting now that new cables won't change anything. If you're ambitious, you should see if someone can measure the actual current draw of the starter. Typical GM gas V8s are between 200-250 amps while cranking in clear-flood mode (pedal to the floor).