Sudden Voltage Drops

[Johnatthebox]

My car has thrown a new electric issue at me-
My alternator works , and my voltmeter reads 14 as I cruise around town until I go up a steep hill and then it starts dropping down to the point of almost dying. If I let off the throttle, it shoots back up to 14 and the lights get bright and eveythings fine until I step on the gas again and it starts dropping again. This only happens when its under a load, like going up a big hill.

 

[Grumpy]

sounds like some cable is shorting out too ground , or somethings, or some connections loose,
I'd get out a multi meter and start trying to find the loose cable, loose ground or loose connection,
on the alternator or battery or engine ground, is the battery shifting position slightly?
have you cleaned the battery terminal cable connections and added anti corrosion paste,
before the cables are re-tightened , Id pull the battery cables and clean and re-connect those as a first step

 

[T-Test]

And run a load test on the battery.

 

[Grumpy]

yeah! good point , your battery may be damaged internally (loose plates)

well? what have you found through testing?

 

[Johnatthebox]

checked for loose grounds and they all check out. Havent gotten a chance to take the battery to be tested at autozone yet, but that is deffintly next. I forgot to mention that stepping on the brake lights will drop it to sub 12 volts too......

 

[Johnatthebox]

Its so weird.... the voltage drops now come in surges as well as when im on the gas. It doesnt have an effect on them if i turn on the headlights or electric fans but the brake lights will dive em down....

 

[T-Test]

Bet it's the battery or no ground from engine to body.

 

[JohnHancock]

I would look at the brake light circuit. Even replace brake light bulbs and sockets.

 

[Johnatthebox]

ordered a new optima red battery today. Hopefully that is the fix

 

[JohnHancock]

That is an expensive guess! Hope it works for you.

 

[T-Test]

. Havent gotten a chance to take the battery to be tested at autozone yet, but that is deffintly next.

That old battery tested BAD???? Or not????

 

[Johnatthebox]

That old battery tested BAD???? Or not????

While waiting for my optima to arrive, I borrowd a good bat from my friends car, and it didnt change a thing. Still dropping and rising, etc.....
My new thought is there must be a wire melted on the header or something, grounding itself out as the motor vibrates. My car rides so low, im gonna have to find a lift, or at least some ramps to get up in there to check

 

[JohnHancock]

Look at brake light circuit! Do you have a trailer plug installed? A bare wire there can swing around with the wind or brake action. Can you get the drop sitting still with brakes applied?

 

[Johnatthebox]

Look at brake light circuit! Do you have a trailer plug installed? A bare wire there can swing around with the wind or brake action. Can you get the drop sitting still with brakes applied?

I cant find any constants in any of this.... I can start it and drive it to the store with no issues, then on the way back it will start surging from 14 down to 12, down to 11, step on the brake and 10.....then bounce right back up to 14 for a block or two, then start dimming again, etc.....
theres no trailer plug, but there are extra wires from previous wirings tucked up in places

 

[JohnHancock]

Look at the brake light switch area. There should be no power past the switch before you apply brakes. Does it only drop with application of brakes? How about turn signals? If they are ok that proves wires may be good from steering column back.

 

[Johnatthebox]

Look at the brake light switch area. There should be no power past the switch before you apply brakes. Does it only drop with application of brakes? How about turn signals? If they are ok that proves wires may be good from steering column back.

it surges on its own at idle or under way, brake lights make an additional drop, as well as the turn signals, but only during the surges. otherwise its 14 volts like its suppopsed to

** ("surge" probably isnt the best word to use. Its actually the opposite of a surge thats happening. ....)

 

[JohnHancock]

Wow. That can be tough to find. I may take the alternator to Autozone for a check.

 

[Johnatthebox]

Wow. That can be tough to find. I may take the alternator to Autozone for a check.

Does the "wire touching header melting thru and grounding out" theory make any sense? That would explain the irregular nature of the voltage drops, right? Maybe?

 

[JohnHancock]

That would make sense if it weren’t for the brake light making a difference. That is the part I’m concerned with. Have you done any work under the dash? Could a wire be pinched under there somewhere?

 

[T-Test]

My car has thrown a new electric issue at me-
My alternator works , and my voltmeter reads 14 as I cruise around town until I go up a steep hill and then it starts dropping down to the point of almost dying. If I let off the throttle, it shoots back up to 14 and the lights get bright and eveythings fine until I step on the gas again and it starts dropping again. This only happens when its under a load, like going up a big hill.

POST #1

it surges on its own at idle or under way, brake lights make an additional drop, as well as the turn signals, but only during the surges.
Post#16


What kind of car?
We need more details about what has been done to the car such as modifications.
Can't have both ways as you state in different posts as in the last 2 in red quotes .

Does the alternator have an aluminum pulley? If so change it to a steel one as from experience the aluminum will let the belt slip.

Have alternator checked.

Isolate problem by pulling fuses and see if problem stops. One at a time.

We can't fix it for you and only make suggestions and if all you do is through money at it, then you would be better off carrying to an electrical shop.