My mom’s truck 2003 Yukon Denali, started having wacky electrical problems today.
The truck stalled while she was taking an exit off the thruway. She said it wouldn’t start just kept clicking and nothing electrical was working. I just replaced the battery last month.
She said she messed with the terminals and got the truck to start. When she got home I noticed the clock on the radio had reset.
I checked the voltage with a multimeter and with the truck off it was 12.5 and with it running 14.4ish and with lights, heat, radio and all other accessories on the voltage barely moved.
Now when I put load on the alternator, blipped the throttle and watched the idle drop bringing the voltage down to 13ish then within a second return to normal.
I took the truck to work and during the whole drive I noticed when slowing down the idle would drop then catch itself so would the voltage. Backing up while turning, or pulling into a parking lot I seen the idle drop pretty low close to stalling.
I understand the alternator works the least in idle and under most load. There is a bulletin out on a similar issue in GM vehicles, but the truck never had this problem.
Gonna check the alt amps.
What should I look at?
Is there a way to check if the alt. diodes are failing?
Any input is appreciated.