Alternator

[slowandsteady]

Late last season the needles on both my tachs, bridge and lower helm, started bouncing. This season neither work and my the gauge says that I am only charging at around 10 volts. There does not seem to be any adverse effects on my batteries. I’m thinking I should get my alternator bench tested. Engine is Perkins 6.354 and I already checked the belt and wire connections. Anyone else experienced this issue?

 

[DavidM]

My guess is that the brushes on your alternator started making intermittent contact and that is why your tachs bounced because they pick up their rpm signal from the alternator. Then they finally failed. Ten volts won't do any charging.



So yes get your alternator checked and rebuilt if necessary. A good automotive electrical shop can do it.


David

 

[rochepoint]

Late last season the needles on both my tachs, bridge and lower helm, started bouncing. This season neither work and my the gauge says that I am only charging at around 10 volts. There does not seem to be any adverse effects on my batteries. I’m thinking I should get my alternator bench tested. Engine is Perkins 6.354 and I already checked the belt and wire connections. Anyone else experienced this issue?

We had the same problem, turned out to be a bad wire from an oil pressure sender to the exciter terminal on the alternator. This circuit allows the engine to start and develop oil pressure before the alternator puts a charge load on the engine.......

PS...same motor.

 

[bayview]

Ten volts is not charging at all. Measure the voltage at the battery with a hand held meter with the engine on and off.

 

[Lepke]

Most auto parts stores will test an alternator for free. If you're handy, you can buy rebuild kits online. I rebuild mine.
New Perkins alternators are under $80 on ebay. Probably $300 from Perkins.

 

[kchace]

At 10 volts you're not charging at all. In fact the battery is getting very low. Not only are you not charging but I suspect there are other issues because if the battery is actually at 10v it is about completely dead.

Ken

 

[FlyWright]

I recently had to replace my start battery for the 2nd time in a year. Turned out that the cause was my port alternator diode had shorted, not blown. The alternator would charge properly when running but after shutdown, the short would drain the start battery slowly.

I discovered the problem by disconnecting the alternator charge cable from the start battery and watched the start battery voltage recover. When the cable was reconnected with the engine off, the battery voltage began to drop again. A bench test confirmed the problem.

I'm not saying this is the same as your problem but alternators can sometimes cause battery problems that you might not expect.

 

[slowandsteady]

Definitely pulling it this week and bringing to a shop to get it looked at/repaired.