Surging headlights and low voltmeter

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Jul 10, 2017
Northern VA
Hoping it’s just a dead battery?

Cranking had been getting weaker and weaker over the last few weeks. Tonight on on my commute home the voltmeter was very low and surging. Headlights were noticeably surging as well. Only when idling, driving was fine.

Would not turn over when I got home and parked. Alternator was replaced a few years ago. Battery is pretty old I think.

If it’s not the battery, how to go about checking grounding?

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The alternator or regulator is toast. Some replacement alternators can croak before the year is out (in my experience).

Replace the alternator and battery & you'll be back on the road.
Some of the 60 series alternators have an external voltage regulator. It's a flat thing, about 2"x2" square that's fixed on top of the alternator via some phillips screws. If it's there, you can replace it easily, it's less than $20, and they do go bad. I carry a spare, and have used it.
Voltage swings like that suggest the alternator, not the battery. But if your battery is old, and has been run dead a few times, you're better off replacing it along with the alternator or the voltage regulator.
FInally got to take a look in daylight and it looks like it might be original or at least OEM reman— not sure with he green band. I haven’t had a chance to look through the previous owners service records yet.

Doesn’t appear to have an external regulator. Fusible links look to be in good shape.

If it’s OEM, should I start with swapping in new brushes? I’ve been searching a lot and these seems to be a good option but may make sense to just spring for the OEM reman.

Found this part: 2737131011 - Brush, alternator. Usa - Genuine Toyota Part

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My vote is for a bad alternator. Replaces the brushes and internal regulator as a first step. Regulator PN 27700-63030

Be aware that a bad alternator can cause a battery to fail. Have both tested before moving forward.
My vote is for a bad alternator. Replaces the brushes and internal regulator as a first step. Regulator PN 27700-63030

Be aware that a bad alternator can cause a battery to fail. Have both tested before moving forward.

Is the internal regulator not included with an OEM reman? I ask because that regulator PN is a $180 which is well on its way to replacing the entire alternator.
It would be included with an OEM reman if you're going the route of replacing the alternator instead of rebuilding it (replacing brushes, etc.).
If you're going to do that, replace the regulator and the diodes as well. It could be them as well and the brushes could be fine.
I’m a noob to all this if it wasn’t already obvious.

So I’m in the process of removing the alternator. I’ve gotten all the bolts out (top, bottom, and adjustment bolt) and pulled all the way out. Belts are loose but it is still pivoting on the bottom bolt point. I’ve tried wiggling and pulling as hard as I can and tapping it with a hammer to free it up.

I didn’t take the air pump out as I couldn’t get the hoses off but it is loosened up.

Do I need to get a pry bar on it? Anything other suggesting?
We were all noobs, so don't apologize. Most of us are still noobs...

Is the bottom pivot bolt out all the way? Then it's just stuck. Stick a pry bar or similar under the alt and lever it off the mounting ears.
Managed to get the new alternator installed. Without completely removing the air pump and only 1 busted knuckle!

Has been driving great. However, idling in traffic tonight the volts, headlights and dash lights were dropping again. Sitting idling in my parking spot in neutral with the lights off the volts stayed pegged at normal. The battery was weak this morning (~30 degrees) and again starting leaving the office (~50). It’s old but was fine after getting jumped and driving around all day plus idling in airport arrivals pickup traffic.

Any thoughts? Bad ground somewhere in the lighting system? Slipping belt? I’ll recheck the tension in daylight.

Also, what should I do with the original OEM alternator. Sell here as is? Rebuild and sell?

Thanks all

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I'm having the same problem with a new alternator in my 60. Voltage reads fine when idling with no lights but with lights on it bounces and my dash and headlights surge pretty bad at idle. Replace the external voltage regulator so I know it's not that. Next is to try a different alternator and see if that fixes it.
The battery is 8 years old and had it replaced this morning. All seems okay. Still dropping a bit idling with lights on but only to 11 to 11.5ish volts (got a cigarette lighter digital reader).

Will continue observing. It may be that the lights are just drawing off the now strong battery. From what I read that isn’t abnormal.

Does anyone have a good list of what to test with my multimeter?
I think you've solved the issues by replacing a failing alternator and an old weak battery.

At idle, the alternator puts out very low amps, so a voltage drop is normal as loads are applied that exceed the amp output from the alternator. With a new strong battery, it can provide the "missing" amps (for awhile, not forever).

One way to help get the most from your new alternator is to run an 8ga fused wire from the + output on the alt to the + on the battery. The stock wiring has the alternator charging the battery through much smaller gauge wires, some of which no doubt have corrosion (which adds resistance). The direct fused wire will reduce voltage drop at low rpm, because you'll have less resistance. Use a fuse that's 20% higher than the amp output from your alternator.

Multimeter battery/alternator checks...I am not an automotive electrician, but here are some approximate guideline values:
At idle, no loads...13.5 or higher volts is normal.
At idle, with everything running (lights, fan, radio, etc) ...11.5 or 11 is normal.
At idle, no loads except the turn signal...11.5 is normal.
At 2000rpm, no loads...14 - 14.8 volts is normal. For some reason I think 14.5 - 14.8 is ideal.
At 2000rpm, all loads (except turn signal)...1/2 volt lower than the no load value.
If you have a monster amp, I don't know what's normal.
It seems to be fine now, it still drops a bit but not enough to be concerned. Not sure what was up
What’s happening here? :doh:


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