Alternator overcharging with new regulator

[datadawg70]

The alternator on my LS180 started randomly overcharging. It would be in the normal range at start up but occasionally after being running for 10+ minutes the voltage would start to climb. At times it would top 18v. Other times I could run it for an hour and the voltage would stay in the 13.5-14.5 range. I assumed the regulator was going bad so I got a new one from my local auto electric shop. It ran normal for a week or so and then it started doing the same thing but it hasn't gone above 17 volts yet. I'm not sure if the new regulator is bad too or there is something else wrong. What should I check?

 

[nflodge]

The alternator on my LS180 started randomly overcharging. It would be in the normal range at start up but occasionally after being running for 10+ minutes the voltage would start to climb. At times it would top 18v. Other times I could run it for an hour and the voltage would stay in the 13.5-14.5 range. I assumed the regulator was going bad so I got a new one from my local auto electric shop. It ran normal for a week or so and then it started doing the same thing but it hasn't gone above 17 volts yet. I'm not sure if the new regulator is bad too or there is something else wrong. What should I check?

The good news is that there are several easy checks you can do to analyze what's going on. The first is to measure the battery voltage at the battery terminals with a trusted voltmeter with the engine running, that is, the battery is charging and compare it with the reading on the voltmeter in your instrument panel. The voltages should be pretty close, or the instrument panel voltmeter is out of calibration.
While charging, the battery voltage should not exceed 14.7 volts with the battery at 70 degrees F or 16 volts at 32 degrees. At colder temps, the voltage can go higher.
If both meters agree and the terminal voltage still goes above 16 volts, the battery could be going bad, the connections at the battery terminals could be corroded causing a significant voltage drop, or possibly the smaller gauge sense wire that sends the battery terminal voltage back to the regulator could be loose causing an intermittent connection.
These are easy checks to do without any disassembly or skun knuckles. Hope this helps.

 

[foton]

I have seen bad grounds cause problems like these you describe. and it could be the ones to the gauge. check as mentioned above post to isolate issue.