akesh45

I had an alternator go bad and mistakenly purchased 2 alternators that only went up to 12 volts. Battery wouldn't get charged as a result and my car would die out.

I purchased a used alternator from a crashed s2000 And put it in. Got a new battery too.

I pulled out the multimeter and been testing it between 15-20 minute drives.

Consistently getting 11.50-12 volts instead of the 13-14 volts some people report. This while idle or under load(revving engine in first gear).

Without car on, I get solid 12 volts.

Is that correct? Also, what are some ways of testing if the alternator is charging the battery successfully?

Perhaps I need to drive for a few hours more? Battery is new but was sitting unused for a week not connected to anything.

Car Analogy

In order to charge, alternator must put out more juice than the normal battery voltage, which is 12.6v. Typical alternator charging voltage is around 14v. Your charging system is not charging.

Ap2low

Go on youtube and watch a few test videos, check for any parasitic draw. Check all of your ground cables, 2 bundles next to the headlights, 2 on the drivers side engine block, bundle right next to the ecu in the drivers side foot panel and last the negative battery cable!

I went through the same headache for eel over a month with worse symptoms than what you have. Replaced the alrernator twice with autozones ones and then dropped $800 on a new one from Honda, along with buying a new battery and I would still have erratic voltage readings. I changed the negative battery cable and terminal to a 2g wire and the car has been perfect ever since. Hope that helps, and good luck!

Billman250

Your car is not charging, check the field voltage going to the alternator.

There is no such thing as an alternator that only goes up to 12v.

When it's charging properly, your volts will read over 13v while running.

Reese914

I have changed the alternator twice, the battery has been replaced with and AGM battery, and the negative battery cable has been replaced with a four gauge cable. My battery reads at 10.4 volts with the head lights on. I’m not able to locate where the other negative/ground wires are. Any help is appreciated.

Car Analogy

So long as alternator is putting out less than 13v, battery won't charge. Alternator output is your issue.

That doesn't automatically mean replace alternator. It means troubleshoot actual issue. You seem like someone that just points at most likely part and replaces it. And if it doesn't fix it, replace something else. Or even replace same part more than once. That isn't troubleshooting.

Youtube for troubleshooting low alternator output. Doesn't have to be S2k or even Honda specific. Charging systems are all conceptually similar.

windhund116

Cars usually won't start with battery voltage under 12-volts. As a rule-out, get a known-good 9-volt battery and measure the DC voltage across the terminals. Just to be sure your voltmeter is good.



One of these. Any brand.

Billman250

STEP ONE is check the fuses. Keep it simple.

One of the fuses in the under-dash fuse block is directly linked to the alternator field supply.

spider2k

ELD fuse

Car Analogy

Can test fuses without removing them. Fuses have test points on top, where you can put meter probes.

Setup: Set meter to diode test mode (aka beep mode). Join black and red probes, make sure you hear beep (one probe might be in wrong place in meter).

Test: Now just place probes on one fuse after the other, making sure hear beep for each one. Probes just go to test points on fuse. Fuse stays installed.

Makes it fast and easy to check all.