07 Ford Focus… Electrical Nightmare?

Posting here because I found a post from 10 years ago with a similar issue. Basically, my alternator had no output, so I grabbed a replacement from AutoZone. Dropped it a few times during install, but it looked fine. Installed it, did the ‘learning cycle,’ drove fine.

Now today, I’m getting 19 volts at the cigarette lighter where I have a volt meter plugged in. Battery is from 2019. My sub system is rated for the stock alternator, and at the time of the video, only the heat and my accessories were on.

No idea what’s going on. I’m stumped.

Your alternator voltage regulator is toast. Replace the alternator.

Nico said:
Your alternator voltage regulator is toast. Replace the alternator.

Just replaced the alternator yesterday though…

Cedar said:

Nico said:
Your alternator voltage regulator is toast. Replace the alternator.

Just replaced the alternator yesterday though…

And you’re getting 17+ volts? That’s bad. Could be an issue with the pulleys—underdrive/overdrive?

@Nico
It’s mounted at the top left of the engine behind the power steering pump. But yeah, I’m seeing up to 19 volts. Do you know what’s clicking when it jumps that high?

Cedar said:
@Nico
It’s mounted at the top left of the engine behind the power steering pump. But yeah, I’m seeing up to 19 volts. Do you know what’s clicking when it jumps that high?

I wouldn’t drive it like that. Best case, you’ll blow a bunch of fuses. Worst case, you’ll fry some modules or even set the car on fire.

@Nico
How do I fix this? Could it be the battery?

Cedar said:
@Nico
How do I fix this? Could it be the battery?

Possibly. An overcharging alternator can damage the battery. Most auto parts stores have a battery load tester—get it checked.

@Nico
Before I installed the new alternator, the battery tested fine, just needed a recharge since the old alternator was dead.

@Nico
I also dropped the new alternator a few times and bent the positive post during install. Probably need another one, huh?

Cedar said:
@Nico
I also dropped the new alternator a few times and bent the positive post during install. Probably need another one, huh?

Yep. 17+ volts at idle is a problem. The alternator is the only thing generating voltage when the car is running, so I’d start there.

@Nico
It only spikes that high under load. Still replace it?

Cedar said:
@Nico
It only spikes that high under load. Still replace it?

Yeah, that alternator is cooked. If it’s spiking under load, it’s not regulating voltage properly. Swap it out before you fry something expensive.

I’d replace the battery first, even if it tests fine. Start there.

Micah said:
I’d replace the battery first, even if it tests fine. Start there.

It’s six years old, so it’s definitely overdue.

Cedar said:

Micah said:
I’d replace the battery first, even if it tests fine. Start there.

It’s six years old, so it’s definitely overdue.

Yeah, you could have a bad cell or something weird going on. I’ve had batteries that test fine but still cause electrical issues.

Swap it out first. If the problem continues, check your grounds and battery terminals. Then check the alternator output with a multimeter.

If it’s still acting up after that, check the fuse box and wiring.

If none of that works… good luck lol.

List of electrical add-ons in my car:

  • Underglow kit (only ground connected since the fuse on the positive wire blew)
  • 4 JBL door speakers, aftermarket radio, subwoofer with amp (installed professionally for stock battery/alternator capacity)
  • Cigarette lighter extender with volt meter
  • Plugged into that: backup camera/digital mirror, radar detector, interior footwell lights

@Cedar
Check alternator output at idle—it should be between 13.4-14.1V.

@Cedar
Might be worth taking it back to whoever installed your radio. Something could be wired incorrectly.