Leece Neville sense wire

[Rick Vyncke]

2004 Beaver Marquis with Leece-Neville alternator that has a sense wire.  The alternator fluctuates every half second or so between 13.5 and 15.5 volts (not normal).  I had the alternator rebuilt and it had no impact.  I recently replaced house and chassis batteries…. No impact.

Current t thinking is a bad sense wire or sense wire connection.  Does anybody know where the sense wire connects?   One end connects to back of alternator but I cannot track where the wire goes from there.  Any help would be appreciated. 

Thanks.

[David T. Richelderfer]

The post I found (link below) seems to indicate where the sense wire is connected.

https://beaveramb.org/forum/index.php/topic,10518.msg71592.html#msg71592

[David T. Richelderfer]

And another post with its link below...

https://beaveramb.org/forum/index.php/topic,3979.msg30681.html#msg30681

[David T. Richelderfer]

and another post...

https://beaveramb.org/forum/index.php/topic,3342.msg25865.html#msg25865

There are many posts talking about the Duvac alternator, sense wire, etc.  I did my search using "alternator sense wire" to find the posts.

[John Fitzgerald]

I am at work but I think it connects at the battery isolation relay.  I am wondering if your battery isolation relay is a part of the issue.  You could run a temporary wire from the DUVAC terminal on the alternator to your chassis battery directly and see if that changes anything.  My sense wire was not even connected when I bought my coach.

[Eric Maclean]

Rick
The sense terminal on the alternator is used to give the alternator a more accurate voltage reading of the battery bank theoretically to off set any volt drop effect caused by long distances between the alternator and the battery bank.
That said in system where the alternator is expected to charged two battery banks the sense wire is sometimes connected to a terminal on a battery isolator which uses large diodes to isolated the two battery and allow one alternator to charge both battery banks ( Duvac is actually a brand name).
On other systems the sense terminal is connected to the primary battery bank.

By disconnecting the sense wire and using a jumper wire to connect the sense terminal of the alternator to the output terminal  of the alternator the voltage should stabilize at a regulated voltage 13.2 to 14.4 volts if it doesn't the regulator in the alternator is at fault.
If this test stabilizes the voltage you need to check the sense wire integrity and the isolator for possible faults.

Hope this helps
Eric

[Rick Vyncke]

Thank you all for your input.  I ran a jumper from the alternator’s sense lead terminal to the chassis battery. Voltage immediately stabilized at 14.2 volts.  Problem identified.  Next I’ll run a more permanent cable.

Thanks again!!!