Alternator excitation

Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
My alternator is only putting out 12.6 volts while running. I had it removed and tested and the guy said it works as intended. He also it was likely the excitation function and it connects to the 61 post. Also, none of my instrument panel lights work. Is this what activates the excitation thingamajig? Could this be the problem?

On a side note, there was nothing connected to the W post and my tach works fine. Any ideas where it is getting it’s free from?
 
Last edited:

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
Good idea to add the wiring diagram but the top of it is cut off. Can you post another photo that includes the whole wiring diagram?
 
Sep 24, 2018
2,549
O'Day 25 Chicago
Does the voltage increase at higher RPM's? I've had a couple of automotive alternators act like they where bad at lower RPM's but seemed OK above 2500-3000 RPM
 
Feb 10, 2004
3,917
Hunter 40.5 Warwick, RI
You have a Volvo engine judging by the block diagram. I have one also. The 12V feed from the battery comes from terminal #1 and it supplies +12V to the entire engine controls. It feeds the instrument lighting, instrument sensors and indicators, and the alternator excitation on terminal 61.

A few questions: Does everything else work correctly? For instance, do the instruments show normal operation? I presume that the engine starts and shuts down OK. Does the sensor alarm work? Does the test button for the alarms work?
Without further clues, I would guess that the +12V that feeds the instrument lighting and the alternator excitation has an open in that circuit. But without further info, that is just a guess. Knowing what else works or doesn't work could give more clues as to the fault and its location.
 
Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
Does the voltage increase at higher RPM's? I've had a couple of automotive alternators act like they where bad at lower RPM's but seemed OK above 2500-3000 RPM
I believe I was only running it at about 2200. I’ll check that when I’m back at the boat Thursday.
 
Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
You have a Volvo engine judging by the block diagram. I have one also. The 12V feed from the battery comes from terminal #1 and it supplies +12V to the entire engine controls. It feeds the instrument lighting, instrument sensors and indicators, and the alternator excitation on terminal 61.

A few questions: Does everything else work correctly? For instance, do the instruments show normal operation? I presume that the engine starts and shuts down OK. Does the sensor alarm work? Does the test button for the alarms work?
Without further clues, I would guess that the +12V that feeds the instrument lighting and the alternator excitation has an open in that circuit. But without further info, that is just a guess. Knowing what else works or doesn't work could give more clues as to the fault and its location.
Yes it is a Volvo Penta 2002. With exception to the start/stop functions, the entire panel is dead. No sensor alarms, lights, or test button.
 
Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
You have a Volvo engine judging by the block diagram. I have one also. The 12V feed from the battery comes from terminal #1 and it supplies +12V to the entire engine controls. It feeds the instrument lighting, instrument sensors and indicators, and the alternator excitation on terminal 61.

A few questions: Does everything else work correctly? For instance, do the instruments show normal operation? I presume that the engine starts and shuts down OK. Does the sensor alarm work? Does the test button for the alarms work?
Without further clues, I would guess that the +12V that feeds the instrument lighting and the alternator excitation has an open in that circuit. But without further info, that is just a guess. Knowing what else works or doesn't work could give more clues as to the fault and its location.
One thing I did over the winter with recommendations on this site, was move the B+ lead to the house battery instead of connecting to the starter. It looks like that could kill the power through the starter and to the relay.
I’ll be back at the boat Thursday and have a three way date with the motor and a voltmeter.
 
Apr 7, 2016
184
Beneteau First 305 Seward, Alaska
Sorry for the above diagram being cut off. Here is a better one. It is different because the one I have uses a key to start. It also solves the tach question.
 

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Oct 22, 2014
20,992
CAL 35 Cruiser #21 moored EVERETT WA
I liked the Stones, but I believe there was a Beach Boys song as well
 
Jul 23, 2009
857
Beneteau 31 Oceanis Grand Lake, Oklahoma
The fuse that feed the instrument panel on my Volvo powered Beneteau failed and caused the previous owner all kinds of problems. When I bought the boat it had a remote start switch and nothing on the engine panel worked. All 4 fuses in the block looked good but the first 2 tested open. Everything started working correctly when I moved the wire to a good spare fuse. Its a fuse with 4 circuits, 1 working and 3 spare. I my case is 2 failed, 1 working and 1 spare. Hope that makes sense.
 
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