Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

[rdc54yty]

Boat is a CC Crowne 340 w/twin Volvo Penta 570A I/Bs. Battery system is 2 batt,2 switch system with a charger.

One of my Paris Rhone 55A alts (port) quit charging a while back. Bench tested it outputs over 14V. In the boat it outputs nil, maybe battery voltage, ~12.4V at the alt + post. Cleaned up connections a little, no change. Ohmed the resistor off the D+ post, ~70 ohms which I think is OK. Ohmed the red + wire from the alt to the solenoid, no resistance to speak of, a couple ohms maybe. Ohmed the ground wire from alt - to the engine block, again no resistance to speak of. Belt is tight. When the boat is not in use I don't run the charger, power in my marina is sketchy.

The engine starts fine. With batt switches in the Both position, port volt meters show 13+ V. When I run the port engine on either batt the port volt meter shows discharge.

Could this be a bad relay? I forgot to check when I was at the boat, 40 mins away.

I need some suggestions.

 

[Don S]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

Make sure the main B+ 8 Ga red wire on the distributor is hooked to the starters battery terminal.

With the engine off, just test for battery voltage at the B+ terminal on the alternator.

 

[rdc54yty]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

Don

"Make sure the main B+ 8 Ga red wire on the ->>distributor<--". Did you mean alternator?

If so I did and it reads battery voltage. Engine off. Not much different engine on either.

 

[Don S]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

Yes, I meant to say alternator.

You should also have a brown wire with a resistor on it, going to the 61 terminal of the alternator. Do you have voltage on that wire when the ignition switch is in the run position?

 

[rdc54yty]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

No I didn't check the voltage. What I did was check the resistor ohms and the continuity of the brown wire between the D+ terminal (not 61 on this alt) and the + coil terminal.

 

[Don S]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

Checking resistance doesn't help, check for voltage on the wire.

 

[rdc54yty]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

OK I'll check volts. Thanks. Assumed since the engine starts and continuity from coil + was good that volts would be good too. Is this the exciter wire?

 

[Don S]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

Assumed since the engine starts and continuity ...............................

Assuming is the best way I know of it being just the opposite, whatever it is.

 

[rdc54yty]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

OK, that was an agonizing 3 hours.

 

[Don S]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

OK, that was an agonizing 3 hours.

Why didn't you just go check the voltage?

 

[rdc54yty]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

I may have. I just didn't write it down a couldn't remember the reading.

 

[rdc54yty]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

With the key on, voltage at the connector, before the resistor going into the alternator, was about 9.8V. It was also about 9.8V at the coil + terminal. Voltage at the D+ terminal was millivolts, about 70mV.

 

[Don S]

Re: Volvo Penta 570A - Alternator Bench Tests OK, Won't Charge in Boat

With the key on, voltage at the connector, before the resistor going into the alternator, was about 9.8V.

You should be seeing battery voltage at that point, if the battery is as ok, you have a poor connection between the ignition switch and that point.

Voltage at the D+ terminal was millivolts, about 70mV.

Sounds like the resistor is open. Remove the resistor from the alternator and the wiring and test it to see how many ohms it is. Doen't rmember what it's supposed to be right off, but measure it anyway and post the results.