Needed to replace alternator on a new to me 49. Noticed that there was voltage to engine even when all (at least I think all) battery switches were off and start battery disconnected. The only way to cut off voltage to engine was to disconnect house battery cables from house supply. Does this make sense? Is there a switch I missed? The switches I located were at house battery bank, inverter, panel on starboard settee facing nav station and at start battery. What am I missing? Thanks for the help.
2009 49 DC System Question
- Thread starter mdaitz
- Start date
Congrats on your new boat! Your 49 has a 100 amp alternator which is wired with a 2 gauge red wire directly to the house batteries. I have not found a switch on my boat. When I changed my alternator to a Balmar 160 amp with an external regulator, I had to disconnect the 2 gauge cable at the batteries. I also marked a warning in the engine compartment to remind anyone working on the engine that the red wire to the alternator is always "hot".
Thanks for the advice. Much appreciated. Thought I was going to go crazy trying to figure it out.
Yes, but this still doesn’t
I just reviewed the battery panel wiring diagram.
As documented, the house batteries disconnect from the alternator feed when the switch is in the off position.
However, the ACR shunts the house to engine feeds when the charger is on, irrespective of the battery switch being on or off.
So, I’m wondering if your charger is on? Try shutting off your AC, and repeat the measurements
Congrats on your excellent boat!
What is curious is that the boat was o. It’s mooring at the time with no shore power within sight. Please keep all ideas coming.
Suggest you download the schematic from the Hunter Docs site. It’s quite straight forward. Good luck
On my 410 the house batteries feed into the start circuit through the inverter selector switch via the battery isolator.
I have a 2004 AC41. Electric has never been modified. Factory original. I have a FP gen set, but no inverter. Start batery is independent. My batery switches DO NOTHING. The schematics are close, but not exact. My suspicion was that Hunter never really updated the diagrams as they modified the systems for inverters, etc. as the technology kept moving. On our boat the only way to truly know that the power is off is to disconnect the batteries.
It is not at all uncommon for a performance alternator to be direct wired to the house battery bank. This yields the opptimal charging performance. In the alternator positive cable there should be a fuse within 7" of the house banks positive terminal sized at 150% of the alternators rated output.
Beyond that it is always a good idea to install, in engine bay & clearly labeled an alternator service disconnect switch. This switch can be de-powered when working on the engine but other than that always remains in the ON position.
A service disconnect switch should de-couple the external regulator at the same time as the alternator output. The reason for this is so that if the switch is forgotten about, and left OFF, the alternators diodes won't be blow running into a zero load situation.
On my Hunter 50 the engine compartment is so tight, I could not find a good place to put a disconnect switch like the one that Maine Sail installed in his CS-36T.