Charging circuitry problem

[dwaynec]

I have a problem with the circuitry for my port engine (DD 8V71N). The alternator is not outputting any charge to the battery bank. I have had the alternator and the regulator tested at our local automotive electrical shop and they are both OK. So my guess is that there is a wire someplace that is broken. Since all of the wiring is in looms, I can't tell what wire goes to what destination, and I am a complete idiot when it concerns charging circuitry.

What I do know is that the three wires at the regulator are positive, negative and field. What I don't know is where the wires originate on the alternator, and what wire(s) connect to the battery cable. I assume that the connection is at the starter solinoid (sp) but all the wiring is painted white.

Can any of you give me a clue as to how this stuff is wired so I can test it?

Thanks

 

[Pascal]

my wiring diagram doesn't show the terminal markings on the regulator and i have replaced the original alternators/regulator with single wire alternators.

the diagram does show a relay activated by the fuel pressure switch on the secondary filter... there is a wire from teh relay to the regulator in addition to a Ground on the regulator and two wires going to the alternator.

 

[yachtsmanbill]

I agree with Pascal on the single wire alternators... not just the Hatts but almost all early alternators were installed with external regulators, and in my opinion were very FRANKENSTEINIEN.
One wire to the battery switch; what could be more simple? Although my OEM system is retired in place (RIP) I plan on a sanitary removal next winter.
ws

 

[Canuck Dennis]

I would suspect the fuel pressure switch, I had that failure on one one of my 12 71 series.

 

[REBrueckner]

I hope you checked to see the drive belt is present and snug.

Next easiest thing to check:the fuel pressure switch: when everything is off, it's likely open....infinite resistance....but check for voltage first, I think there's 12volts on one side...With engine running, it should be closed..no resistance. If the switch is failed open, then you'll not get any field current so the alternator is still off though spinning....


At the alternator, you can lift the wires one at a time and check distant ends via ohmmeter....Check each one in turn for voltage FIRST as if there is any VOLTAGE it will damage/ruin an ohmmeter....the one that is plus is connected to your battery positive. Label each with dymo tape as you identify them. At the fuel switch, when you get zero resistance on one wire at the alternator end, it's the field wire....Likely the heavy cable is to your battery, so one wire will likely show 12volts at the alternator from the battery. The negative ground wire will show zero resistance to engine/ground...

 

[dwaynec]

Hmmmmm. I never gave the fuel pressure switch on the secondary filter a thought. I replaced that last year on the port engine since the original had started to leak. I bought the switch at our local DD dealer, but maybe it is the wrong switch or defective.

Are the switches normally open or normally closed? In saying that I am assuming, maybe erroneously, that normally open means that in the absence of fuel pressure, the switch is open, and when there is fuel pressure, the switch is closed. Is that correct, or do I have it backwards?

Thanks.

 

[REBrueckner]

You have it correct...switch closed when engine is operating and completes your alternator circuit...

 

[dwaynec]

OK, I assume I can check the switch with a voltmeter by touching the contact that is toward the rear of the engine and the exhaust manifold and if the switch is closed I should see 12V, correct?

 

[Pascal]

engine running you should see power on both side of the switch. put the neg lead on a ground and the the pos lead on either side. you should find 32v (or 12v if your boat was converted) on both terminals with the engine runing.

sometimes the swtch also power hour meters, do you have them? are they working?

 

[dwaynec]

I just got back from the boat checking the switch. On the one side,it shows 12V with or without the engine running. On the other side it shows 0V either running or not running. I can't see anything on the switch that would indicate it can only be hooked up one way, and there were no instructions with the switch when I bought it. The way the switch is currently hooked up is with a single large (maybe 8 gauge) wire on one pole and two smaller ( 10 or 12 gauge ) on the other pole. This is the way the switch is hooked up on the other main and the charging circuitry works correctly. The only difference is that on the stbd engine the large wire is installed on the rear post and the two smaller wires are on the forward post. My guess is that I will be running out to DD and getting another switch.

As for the hour meters, one of the PO's changed them out and set up the new meters so the run whenever the ignition switch is turned on. I have that on the todo list as sometimes the ignition switch gets left on when opening the windshield and the meter is running.