Car still has electrical problems and high voltage after replacing parts
Persistent vehicle electrical faults like high voltage spikes and limp mode often continue even after replacing major components like the alternator, battery, and ELD. This leaves drivers completely stuck after trying everything, unable to reliably diagnose the root cause of the ongoing system failure.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
- This comes up 10.9× more often in r/MechanicAdvice than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
Car still has electrical problems and high voltage after replacing parts
- 1replacing the alternator2 people mentionedDid this help you?
- 2replacing parts such as the alternator, battery, and ELDDid this help you?
- 3clearing diagnostic trouble codesDid this help you?
- 4cleaning contacting surfaces with sandpaper down to bright metalDid this help you?
- 5applying a protectant like anti-seize, cold galv, or soft sealDid this help you?
- 6connecting a new ground wire for testingDid this help you?
- 7checking and cleaning all grounds across the vehicleDid this help you?
- 8Testing the battery and alternator at an auto parts storeDid this help you?
- 9Checking or cleaning the positive terminal cable and battery connectionsDid this help you?
- 10Replacing or getting the instrument cluster rebuiltDid this help you?
- 11Matching the layout and amperages currently in the box rather than the official diagramDid this help you?
- 12Rotating the diagram to see if it alignsDid this help you?
- 13Checked interior and under-hood fusesDid this help you?
- 14Tested battery with a multimeter and at auto parts storesDid this help you?
- 15Left the battery unhooked overnightDid this help you?
- 16Tried jump-starting the car with another vehicleDid this help you?
- 17Replaced the starter completelyDid this help you?
- 18checking all fusesDid this help you?
- 19inspecting main ground straps for internal damageDid this help you?
- 20Shifting manually between P and D to temporarily handle transmission engagement issuesDid this help you?
- 21Testing the battery and alternator to diagnose the root electrical problemDid this help you?
- 22Having the battery tested at an auto parts storeDid this help you?
- 23Checking battery and wiring voltage with a multimeterDid this help you?
- 24Replacing terminal connectionsDid this help you?
- 25Disconnecting the battery for 20 minutes to perform a hard resetDid this help you?
- 26Taking the vehicle to a shop to have the PCM reprogrammed or replacedDid this help you?
- 27Never letting the other person hook up the jumper cables themselvesDid this help you?
- 28Testing wires and fuses with a multimeter to trace the fault.Did this help you?
- 29Asking online mechanics for a diagnosis before paying a professional auto electrician.Did this help you?
- 30Removing the newly installed parts to see if the error clears.Did this help you?
- 31Reinstalling the components one by one to isolate the faulty connection.Did this help you?
- 32Disconnecting the battery in an attempt to reset the error.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Honda accord is going through some electrical issues. It first started with losing power to pedal . While driving Aka limp mode alternator and battery were replaced within the year . So I replaced the Eld (charged the battery before eld replacement ) but I’m still having issues with high voltage.”source ↗
“The dash bings and bongs at me alot. Sometimes the voltage dips to 9 then right back up again.”source ↗
“When this happens it goes to Unkown driver and when it comes back up to 14 volts it returns to Driver 1 and bings and bongs at me.”source ↗
“At wits end. I very dumbly in a rush hooked up my truck that was dead, backwards. It starts and runs, till it doesn’t. Worse when I drive it, dies faster.”source ↗
“The car starts and runs, but then dash lights start coming on. The transmission won't really engage while driving and jerks — I have to shift to P and back to D, and sometimes I get the same issue with R.”source ↗
“I had the battery and alternator tested, and it's not charging at all. I’ll probably need to replace alternator. But could that be what's messing with the transmission not engaging?”source ↗
“Also why is is so hard to find a mechanic that knows how to work on wiring?”source ↗
“Like why tf mechanics didn’t get taught everything about a car like why only Facebook marketplace 2026 mechanics only know how to unscrew and screw stuff on the car together but no wiring skills.”source ↗
“they ended up trying to start it before she had a chance to start her car and her car then wouldn’t start and you could hear it clicking like it was trying to turn on,”source ↗
“a check engine light popped up (the picture) and it won’t stop doing it now any ideas on if the bad ground would be what have caused it I’m very stumped any advice would be appreciated.”source ↗
“Originally it worked but after trying to sort out the steeringwheel controls i mustve done something as I no longer got power to the headunit.”source ↗
“When I checked the red wire now though the voltage keeps rising constantly. I also hear a faint electrical buzz to the right of the engine (facing from the front of the car) when accessories at turned on.”source ↗
“I dont plan on fixing it myself unless its unbelievably simple but id just like to know whats wrong and what cost id be looking at to repair whatever is wrong.”source ↗
“I installed all the parts and wanted to move the truck but I got the Reduced engine power message that was never there so I am pretty sure some connection is bad.”source ↗
“At first I thought it could’ve been my battery, so I took it to autozone and had it tested. The guy working there told me it was a perfectly healthy battery. I then spoke to a buddy and he said he heard the same noise in his car about a year ago and the problem was the alternator. Can anybody please try to diagnose what’s going on.”source ↗
“My 2018 Chevy Silverado is throwing codes and I have absolutely tried everything.”source ↗
“I am absolutely lost on this and any help is beyond appreciated!”source ↗
“I guess I slipped, and got the hammer stuck. Couldn’t exactly see what happened, I’m assuming I touched the positive terminal to the car body somewhere and grounded it out, because it was sparking really bad for 2-3 seconds before I was able to yank the hammer out of where it was stuck.”source ↗
“The cluster was acting weird like it wasn’t behaving like normal when you turn the key, and it dings at me when I turn the key. And my key fob stopped working.”source ↗
“I replaced the starter completely, and nothing again. I can hear it trying to engage when I turn the key but nothing.”source ↗
“I looked up the fuse diagram for this specific year and model, but the layout and amperages in the car don't really match up with the official diagram.”source ↗
Where this came up
People with this problem also raised
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- 7Car battery leaking acid with no warning lights
- 9Dealership can't figure out why my car won't start
- 4Why does touching my breaker panel turn my electric dryer back on?