Voltage Issue

[PurpleCedarPlug]

Can anybody help me figure this one out?

Boat 99 CC 28 Cummins 6BTA 220HP

Voltage gauge on Port motor reads no more then 12 and will drop down to 11 or lower, then jump back to 12 at idle and at cruise.

This past weekend after fishing, pulled in for fuel, turned motors off, left main on and battery switched on. After refueling boat (@20mi) Went to start Port motor and it struggled to turn over, but eventually did.

We checked all components with a meter: Gauge works correctly, batterys are good (We even switched Port and Starboard Btry thinking Port was bad), alternator is good, Isolator is good, battery charger (dock side) is good.

Something is drawing power from the Port side and I can't figure it out..

Someone suggested maybe the Voltage Regulator which is a part of the alternator may be bad..

Any suggestions would be appreciated. I am at a loss??

Thanks,
Ed

[Tswann]

Try . . .

If you checked all those items, I would tend to look at the ground side of the motor and make sure you have good/clean/tight connections . . .

The fact that she struggled to turn over sends me towards a loose ground or battery cable. Check the inboard, rear side of the port block for the primary connections. Makes sure the cable crimps are in good shape and have good/solid contact. You can pass a lot of voltage through a crappy connection, but passing high-load/high-amps is another issue . . .

Voltage regulator in the alternator -- maybe. Of course the cycling below eleven back up to twelve or so is/are the grid heaters cycling on and off.

[PurpleCedarPlug]

Tswann,

Thanks for the quick response.. I will check the ground to make sure everythings clean and tight.

Question?

Grid Heathers cycling on and off. What is this?

Thanks
Ed

[outriggers]

First check the output of the alternator at the input of the isolator. It should be around 14.3v or so. The isolator will drop around .6v at the output as it goes thru a diode to isolate the other battery. You should have at least 13.5v there. Anywhere you measure after that you should have the same reading. If not you have some bad connections. You battery should show the same amount with the engine running. With it off it will read around 12.5v fully charged when it settles down or after you hit it with a short start to knock it down to a static condition. You should get at around 10v at crank or you have a bad/weak battery.

Feel all your connections to the starter if the voltage is low at the starter terminal. You could have a bad ground or pos battery connection problem.

You shouldn't have a fluctuating voltage at anytime if you don't have large loads going on and off. I believe the grid heater is the air intake heater for starting cold. I don't have the engine but that's what it sounds like. They draw a lot of current and shouldn't be operating when the engine is hot.

[Tswann]

Voltage

With the 6Bs (and 4Bs for that matter) in the boat you will have voltage fluctations as the grid heaters cycle on and off. Typically these will occur for the first 20 minutes or so or until the boat reaches 1200 rpms. This load is large and will cause a drop from 14 volts to 10 or 11 . . . These are air heaters for start assist and low rpm smoke control. After the initial 20 minute or 1200 rpm cycle a thermistor in the aftercooler will control them if incoming air temp drops at the aftercooler . . i.e out striper fishing and the ambient temp is low and your are at dead low idle. Grid heater worth vs stress on the batteriess and value is up to debate. Most people will install a switch to manually cycle these on and off during those cold winter mornings and others will wholesale remove the emm and grid module from the boat completely . . . You can verify any of this by going to boatdiesel.com and search 6B + grid heaters . . .

Additionally, on a 6B install you will NOT (and should not) have both alternators plugged in at the same time. This is by design and how CC installs them. In essence, you will only have one alternator plugged up at any given time (and the other is in reserve) feeding the isolator and battery system. There is a three pin connector on the back top of the alternator and if you look at both motors one will be plugged in and the other will not - typically the unsused connector will be wire tied right behind the alternator. If you would like to test you alternator you can simply swap the alternators by plugging and unplugging and check your results. Of course do this while the boat is not running and in the key off position.

On my personal 28 I used to swap which alternator was plugged in every time I changed my secondary fuel filters . . . I felt like it wasn't fair for one to do all the work all the time . . . .

Feel free to give me a call/email if you need anymore guidance.