My 4cyl sonoma tonight the lights would randomly flicker dim then bright vert quick fluctuation. I noticed all the lights doing it and the volt gauge bouncing from 11-14v I shut it off to get gas and when I restarted it the gauge went to 10 and then over the course of 20 seconds slow rose to 14v alt is my first thought. Any ideas/opinions.
200 gmc sonoma voltage issue
- Thread starter ram_man
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If you hit the brakes does all the lights go nuts in dash. Mine was caused by belt tensioner. Let me know if that helps.
OVERKILL
$100 Site Donor 2021
Aren't you a mechanic?
Don't you get paid to do this all day?
Take to your place of work and test it?
Alternatively autozone, aap, or your favorite autoparts store.
Edit: overkill beat me to posting
Alternator sounds like a good starting point but like almost all your threads you don't give enough details and you do this for a living seems like this would be extremely easy to diagnose in person??
This post is the equivalent of Overkill posting in the computer section questions about subnetting.
Take to your place of work and test it?
Alternatively autozone, aap, or your favorite autoparts store.
Edit: overkill beat me to posting
Alternator sounds like a good starting point but like almost all your threads you don't give enough details and you do this for a living seems like this would be extremely easy to diagnose in person??
This post is the equivalent of Overkill posting in the computer section questions about subnetting.
Short brushes in the alt?
It's not the alt, it's something dumb.
What, IDK.
But I bet the PCM or BCM controls the alt, as you saw over your 20 second voltage rise after starting it.
I'd go through the dash grounds and random battery connections, underhood fuse box, etc.
What, IDK.
But I bet the PCM or BCM controls the alt, as you saw over your 20 second voltage rise after starting it.
I'd go through the dash grounds and random battery connections, underhood fuse box, etc.
I think the alternator is dying.
Look up all the diagnostic tests you can do on it, but I'd definitely start there.
Look up all the diagnostic tests you can do on it, but I'd definitely start there.
I've read other threads of these trucks doing this but with varying solutions. Hitting brakes doesn't matter. And I'm an entry level mechanic. I do some stuff its not like i know everything. We have test equipment at work but rarely have time to mess with our own stuff their. I will be checking connections and everything I can today.
OVERKILL
$100 Site Donor 2021
Originally Posted By: eljefino
It's not the alt, it's something dumb.
What, IDK.
But I bet the PCM or BCM controls the alt, as you saw over your 20 second voltage rise after starting it.
I'd go through the dash grounds and random battery connections, underhood fuse box, etc.
Actually, when the 2G alt went out on my F-250, it showed "charging" but was similar in behaviour to the OP's. I came out the next morning to a dead battery. The alt had shorted internally and killed it.
The alt, verified with a DVOM and then if that looks funky, have it bench tested, is the first place I'd start.
It's not the alt, it's something dumb.
What, IDK.
But I bet the PCM or BCM controls the alt, as you saw over your 20 second voltage rise after starting it.
I'd go through the dash grounds and random battery connections, underhood fuse box, etc.
Actually, when the 2G alt went out on my F-250, it showed "charging" but was similar in behaviour to the OP's. I came out the next morning to a dead battery. The alt had shorted internally and killed it.
The alt, verified with a DVOM and then if that looks funky, have it bench tested, is the first place I'd start.
Sounds to me like a bad connection in the primary electoral system.
First, clean the battery posts and cable clamps. If it still fails, check the ground battery cable where it attaches to the engine. Could be a bad connection to the alternator. Check the wiring .
Use a step by step approach, start at the battery and work your way through the system. Does your car have a ground strap connecting the engine to the body? If so, check it. My mopars all have this grounding strap, it can cause all sorts of problems.
Good luck,
Wayne
First, clean the battery posts and cable clamps. If it still fails, check the ground battery cable where it attaches to the engine. Could be a bad connection to the alternator. Check the wiring .
Use a step by step approach, start at the battery and work your way through the system. Does your car have a ground strap connecting the engine to the body? If so, check it. My mopars all have this grounding strap, it can cause all sorts of problems.
Good luck,
Wayne
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