Bad voltage regulator on new alternator?

[KCscout]

Replaced my alternator, the old one whined for a few weeks and then finally died. Started up my 4runner and everything was good for a little while. I now have surges of voltage and i can feel the alternator putting a load on the engine during surges. All my connections are tight. I even ran a ground from the alternator to the battery ground to eliminate a bad ground. Voltage is either low at 11v or has spiked to 17v. Ill attach a few pictures of voltages i have. Anyone have any extra troubleshooting tips before I replace the alternator again?

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[KCscout]

And for reference this is what the voltage looks like when its not surging.

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[81runner]

What kind of alternator did you get? I had serious trouble with rebuilt alternators, wound up getting a fresh denso unit. Been fine ever since

 

[Toyrundrive]

I'm running a mechman alternator monitored by an analog voltmeter. It too about two weeks of occasional City driving for it to even out. Unfortunately the shop that installed it for me (id have done it myself but my steering pump exploded and that pulley is in the way of the last alternator bolt on the V8) decided to put the larger, stock pulley on it without my consent so that could have something to do with it taking so long to even out.

 

[riceandpho]

I'm running a mechman alternator monitored by an analog voltmeter. It too about two weeks of occasional City driving for it to even out. Unfortunately the shop that installed it for me (id have done it myself but my steering pump exploded and that pulley is in the way of the last alternator bolt on the V8) decided to put the larger, stock pulley on it without my consent so that could have something to do with it taking so long to even out.

when you run a high output alternator, they recommend an inch shorter belt since the pulley is smaller.

 

[riceandpho]

Replaced my alternator, the old one whined for a few weeks and then finally died. Started up my 4runner and everything was good for a little while. I now have surges of voltage and i can feel the alternator putting a load on the engine during surges. All my connections are tight. I even ran a ground from the alternator to the battery ground to eliminate a bad ground. Voltage is either low at 11v or has spiked to 17v. Ill attach a few pictures of voltages i have. Anyone have any extra troubleshooting tips before I replace the alternator again?

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i think some guy had the same issue, and it turns out he tore up one of the wire at the 4 pin plug, before you put the battery in, did you charge it up on an external charger to make sure the battery is still good? alot of people dont know that after an alternator swap, having it to try and recharge the old battery can kill it.

 

[Toyrundrive]

when you run a high output alternator, they recommend an inch shorter belt since the pulley is smaller.

I'm aware of that, I told that to the installer, he still swapped the pulleys without even asking. I didn't find out until I was packing up some old parts into my truck for a road trip and saw mechman written on the O'Reilly alternator...

 

[KCscout]

i think some guy had the same issue, and it turns out he tore up one of the wire at the 4 pin plug, before you put the battery in, did you charge it up on an external charger to make sure the battery is still good? alot of people dont know that after an alternator swap, having it to try and recharge the old battery can kill it.

I believe the alternator plug does not play a role in voltage regulation but I could be wrong. I was under the impression that plug is responsible for turning the dash light on for the battery. Also i put the battery in at 12.6 volts, so no problems there. I'm going to replace my alternator tomorrow and I will update if the problem goes away for anyone browsing with the same problem. Also had some spikes over 20v and a few burned out bulbs. Fairly sure the internal voltage regulator on the alternator is to blame.

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[KCscout]

i think some guy had the same issue, and it turns out he tore up one of the wire at the 4 pin plug, before you put the battery in, did you charge it up on an external charger to make sure the battery is still good? alot of people dont know that after an alternator swap, having it to try and recharge the old battery can kill it.

Turns out I didnt understand how internally regulated alternators worked. You were 100 percent right. Sensing wire apparently didnt have a good connection. I took off the plug and everything looked good. Put the plug back in and pushed it on as hard as i could. Problem seems to be fixed for now. Might have to replace that plug in the future.

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[KCscout]

By chance if anyone sees this that has the same problem, I did end up having to change my alternator out. The problem kept coming back. 2nd new alternator in the 4runner and all my voltage problems have been fixed.

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