new battery new alternator battery looses charge at night and motor will not turn over
I presume a new battery an alternator were installed to address a dead battery in the morning problem. Well, at least you have those new parts … The best way to diagnose this sort of problem is a phantom current drain shop test. Should be 75 mA or less. Has that test been done?
Some things the car owner can do: Park car, let it sit unused for an hour or two. Are any lights on? Brake lights, interior lights, engine, trunk, glove compartment lights?
1 Like
I’m guessing you are just throwing parts at it and hope they stick without doing a proper diag???
George gave a pretty reply…
You need to put a at least a test light in series between the positive battery terminal and battery… Let vehicle sit for about an hour and watch the test light, should be dim, of bright (like going from pos to neg battery terminals (B+12 volts)) then start pulling fuses one at a time until light goes out or very dim, same with relays… The problem will be in that circuit and then you start checking that circuit…
Make sure you don’t have anything plugged into a power port (cig lighter) that has key off power (if available) I have seen some vehicles have both key on and key off power ports, don’t know about yours…
1 Like
If your Yukon battery drained overnight, that usually points towards a parasitic drain, meaning something in your car is drawing a current when it shouldn’t have been.
1 Like
Parasitic drain seems likely especially if you have an aftermarket radio, remote start, trailer brake controller or sub woofer. Start with those.