Regulation Issues

Charging Voltage Issues

This post is to just keep track of the issue we noticed again this last trip.

Here's the overview

We motored up the IntraCoastal Waterway (ICW) on Tuesday, some of the bridges are just far enough apart that we can only make them if we push our speed up a bit. That means running the engine at around 2,000 rpm for about 15 minutes. We monitor the Engine Status by checking the Engine Control panel about every 10 minutes or so, but after about 4 hours into the trip, I noticed that the Engine Tachometer was reading 0 - ZERO but everything was running just fine. And that is the issue that I'm addressing here.

More Background.

On Friday, I noticed. that there is about a 1.2 volt drop from our electrical panel to the instrument system. For example, at one point, the GPS was showing 12.6v when the Digital volt meter connected to the Bus Bar in the Electrical Control panel is reading 13.8. That's voltage drop is too high, so I need to address that, but it's important right now to consider when diagnosing the issue.

While motoring at around 1,000 rpm, the Tachometer would drop to zero and at the same time the engine sound would alter, I'm guessing it was due to a reduction in Alternator Load because the voltage display would also drop to around 12.7v (it was be higher when the Tachometer actually displayed the engine rpm.). Every few minutes, the Engine sound would alter and at that time the Tacho would correctly show the current rpm. This repeated itself, even with no throttle alteration at all, almost consistently. When we throttled up (Tach showing 0 rpm) to around 2,000 rpm, the Tach would come back on line and show the current rpm, and the voltage display at the helm (GPS) would also go backup to around 13v.

Conclusions

My current (no pun intended) conclusions are that there is an issue with the External Regulator and possibly the wiring of the regulator to the Alternator.

Here's my reasoning: 

• When the Alternator is charging, there's a greater load on the engine, and the voltage display shows the charging voltage.
• When the Regulator reduces the charging voltage, it may be turning off the control voltage to the Alternator completely, thus also removing the voltage that is used to sense the Tachometer input.

The wiring from the Regulator to the Alternator was just replaced last year when I did a complete engine harness upgrade, but that could still be an issue.

Further Research

I'm going to inspect the Regulator connections, both at the Alternator and the Battery voltage sensing connection. I have no reason to suspect the connection at the Engine Control panel as the issue is very consistent and a bad connection would either be open or intermittent, and that's not the case.

I do have a spare Regulator and intend to wire that up at some time, as it also is connected to the Link charging system that we have onboard.

Meanwhile, if you have any ideas on this issue, they would be welcome.

Paul