Battery issues

I recently just got a Cobb Accessport and started noticing that the voltage on my car were a little off. When I first start the car, the car starts fine and the voltage start of near 12.4. As I drive, the voltage gradually starts dropping until around 11.4. Now mind you, this is all with A/C on, radio, headlights, foglights. Everything on. I have already checked the battery and the guy told me battery was no good. Battery voltage was still the same. Guy tells me to change alternator, I change it, Voltage still the same. What should I do? Car is starting up fine in the morning and at all times but I do feel like the A/C while driving sometimes goes and I feel like it might be related to the electrical issue. Accepting all inputs let me know what you think.
Picture below is at idle after a short drive.

get a volt meter from someone, car off, battery should have 12+ volts at the terminals, with car running you should get 14+ volts at the terminals.


don't know about your COBB

I have already checked the battery and the guy told me battery was no good

Click to expand...

did you replace the battery?

Mr2U said:

get a volt meter from someone, car off, battery should have 12+ volts at the terminals, with car running you should get 14+ volts at the terminals.

Click to expand...

best advice you can get. trust but verify.

if the DMM/Volt_meter measurements line up, then you have a charging system issue.

relic1 said:

did you replace the battery?







best advice you can get. trust but verify.



if the DMM/Volt_meter measurements line up, then you have a charging system issue.

Click to expand...

Yup, replaced battery and alternator brand new. I’ve taken it to the Advance Auto parts to get everything tested, says alternator is no good. Took it to a friends shop he measured it with volt meter and he also says it was alternator. Bought brand new alternator and replaced t myself. Still the same low voltage. I don’t know what else to change.


Sent from my iPhone using Tapatalk

new alternator and battery... both being bad is rare, yes they can take each other out if they are bad enough, but usually the car doesn't start or run properly before then.

have you used a meter to check the battery voltage? (most stores have a cheap one for <$10)

relic1 said:

new alternator and battery... both being bad is rare, yes they can take each other out if they are bad enough, but usually the car doesn't start or run properly before then.

have you used a meter to check the battery voltage? (most stores have a cheap one for <$10)

Click to expand...

Yeah checked with a meter but looked further and noticed the ground wire was a little hot to the touch so I added another ground to the alternator and sure enough the voltage peaked up to 13.6 on idle. My guess is that the ground wire that comes with the car is faulty?

geramy1232 said:

Yeah checked with a meter but looked further and noticed the ground wire was a little hot to the touch so I added another ground to the alternator and sure enough the voltage peaked up to 13.6 on idle. My guess is that the ground wire that comes with the car is faulty?

Click to expand...

If the ground wire is hot, it's probably not connected well. Check for a good, tight connection, and make sure that there is no corrosion anywhere, a poor connection will cause resistance (heat) and limit the charging ability of the alternator. Check the entire wire, at both ends. If there is any signs of burn marks, or any obvious damage, replace it. Check all of the cables in the circuit, especially the ones that were disconnected to swap the battery and alternator.

geramy1232 said:

Yeah checked with a meter but looked further and noticed the ground wire was a little hot to the touch so I added another ground to the alternator and sure enough the voltage peaked up to 13.6 on idle. My guess is that the ground wire that comes with the car is faulty?

Click to expand...

glad to hear you got it figured out. :thumbsup:

Ground wires do go bad, since they are a connection between the engine and chassis they get wiggled and vibrated a lot. (differently at both ends)
All though typically speaking they last longer than the age of our cars.... there may have been a small defect in the wire or crimps, or there was something that damaged it at one time, which weakened it. :iono:


to expand on gijoewoz's comment, any wire that gets hot is suspect. It means there is too much resistance to the current flow. (either a defect in the wire/crimp/connection OR too much current flowing)