2017 Grandsport.
Yesterday on my way home my guage cluster would get bright then dim. Periodically all the guages would stop and various troble lights would come on and then go off.
the car itself runs fine. No loss of power or erratic idle.
This morning it started doing it again after about 5 minutes of driving.
I unplugged my radar detector and dongle for androidauto.

Turned the car off and sat for about 5 minutes.

Cranked back up with everything unplugged.

It did it again after I pulled out of the parking lot.

I plugged everything back in and drove the 20 minutes to work.

It did not do it again all the way to work.

The alternator appears to be charging and the battery is about 8 months old.

Anybody seen this? Where to start troubleshooting?

Thanks
Wade

 

You definitely need a good DVM and a scanner to start otherwise you're just guessing.

Problems like this will take some good troubleshooting.

Sounds like a wiring or module issue, something is intermittent.

Could be something simple like a battery or connector or something very complex, if it's the latter tracking it down is the hard part.

 

Had something very similar last year. Your alternator may be actually overcharging. There is a voltmeter display in the gauges. If it’s showing in the very high 14s or going into the 15s, that may be the culprit.

 

Just a random thought: check the small black voltage sensing wire attached to the negative battery cable clamp. The wire is important for correct charging and is easily broken.

See wire attached to BLUE stud / nut:


Voltage sensor wire attached to negative battery cable clamp at BLUE stud.

Ron

 

yes, I check mine every time I drive.

 

Hopefully something simple - perhaps that small wire on the battery. Good luck.

 

Yesterday before I left work I checked that wire and wiggled it a little. All seemed fine. I set the voltmeter guage to display and cranked it up. It stayed right around 14 to 14.5 to start.

I drove 2 miles and got on the highway. Guage was still 14 or a little above.

It did the power sure thing twice in a row. I did not se a high spike before the guages died.

After the surge happened twice it never did it again the rest of the 45 minute drive.

The guage stayed pretty steady at 13 and never went above 13.5.

THIS MORNING

Cranked the car after sitting overnight. Guage was 14 to 14.5.

After 5 minutes of driving the surge started again.

Guage stayed in the 14 to 14.5 range all the way in but I can't say it stayed steady.

The headlights and infotainment screen do not seem to be affected

I do have a diagnostic tool but not sure if it will be of any use. I will plug it in anyway.
I am also going to disconnect the battery to reset everything.

Any other ideas or suggestions?

Thanks!
Wade

 

Charging voltages sound reasonable - higher when starting and drifting lower as the battery charges. The charging voltage is set by computer based on battery state of charge and accessory loads such as A/C and headlights... There's a thread with the details somewhere.

You might also cycle the dash dimmer switch a few times to wipe any contacts clean - but I doubt dimmer or ambient light sensor is the issue since you also get various warning lights (which ones?).

Auto parts stores can check the alternator and battery while in the car, but not sure how good the test is for the computer controlled alternator.

GL

Ron

 

I'd check the dash light dimmer switch itself

 

Maybe a loose connector or ground connection at or around the dash panel? It sounds to me like it occurs after the car is put into motion.

 

dealer told me c7's can run from high 11's to low 15's, so i don't worry anymore!!

 

Start with the simple things first, make double sure that ALL battery connections are clean & tight

 

Your alternator could be intermittently spiking the voltage due to a failing diode inside of it. You would need a scope to see this spike and it would be of a short duration. Also the voltage regulator which is also inside the alt. could be starting to fail intermittently.

Does your radio ever have a hum to it, easiest to notice when you have a moment of 'Dead Air'. This also indicates a bad diode inside the Alt.

 

Thanks for all the replies. Last night I started to drive it, and it was the worst it has been. The lights in the dash, messages and gauges continuously cycled. As far as which messages, I would have to say, ALL OF THEM! I have seen messages pop up I've never seen before. seatbelt light comes on and goes out and bell rings. Only the dash is impacted. Infotainment and other lights are fine. No hum in the radio. Car runs and drives fine. I will clean all the connections to the battery and reseat the cables and see if that works. If it doesn't I will see if autozone can check battery and alternator.

Here is what an AI search turned up:

Top Possible Causes (in likely order for C7 Corvettes):

1. Loose/damaged small black sense/ground wire on the battery negative terminal (very common on C7s): GM issued a specific diagnostic tip (PIC6439 / related to DTC B1517) for exactly these symptoms on 2014-2019 Corvettes. After battery service, the small black wire attached to the main negative cable can become loose, rotated, or pulled out. This causes intermittent voltage/ground issues that make modules, gauges, and sensors act up exactly as you describe.
   
   • Fix: Inspect (and often just reseat/replace) the battery cables, focusing on that small black wire. Many owners report this instantly resolves flickering/blackout gauges.
2. Failing or intermittent alternator / voltage regulator: Alternators can cause voltage spikes/drops, leading to bright lights (surges), then dim/out gauges when voltage sags. The ~13-14.5V fluctuation fits a weak or over/under-charging alternator, especially under load. C7s have had reports of this causing dash surges and sensor glitches.
   
3. Battery issues or poor connections: Weak/dying battery, corroded terminals, or loose main cables. Even if it starts fine, an aging battery can't buffer voltage fluctuations well. Modern GM smart charging systems do cause some normal fluctuation (12.8-15V range), but yours combined with symptoms suggests a problem.
   
4. Other grounds, wiring harness chafing, or BCM issues: Loose grounds elsewhere, damaged harness (common in engine bay), or BCM glitches can cascade into multiple module faults. Less common but reported on C7s with similar intermittent dash problems.
   

Recommended Next Steps:

• Scan for codes (OBD-II scanner that reads all modules, not just engine) — look especially for B1517 or charging-related codes.
• Test voltage properly: Monitor at the battery and alternator output while driving (or have a shop do it). Watch for drops below ~12V or spikes.
• Inspect battery area first — it's free/cheap and matches many identical C7 complaints.
• Have a shop (ideally Corvette-savvy or GM dealer) load-test the battery and alternator.
• Check/reseat all visible grounds and battery connections.

This is a known pattern on C7 Corvettes, so start with the battery negative wire per the GM bulletin. Don't ignore it — prolonged issues can damage modules. If it's the alternator, replacement is straightforward but confirm first.

 

how old is the battery??

 

I replaced it last October.

 

thanks, you hadn't motioned, sometimes the problem!!

 

Oh i thought your dash lights were going brighter and dimmer, not freaking out. The gauge cluster comes out and has a plug in the back. I guess that will be the last place you check