My boat has twin Cummins diesels - model 6CTA8.3-D(M)2 (mechanical not computer managed), fitted with 24V Delco 22Si alternators, one of which, at idle of 600 RPM, delivers highly fluctuating output –cycling from around 15-20 A at 27-28V to 23-24V and 60-70A. Each cycle lasts 5-6 seconds only.
All current goes only to the batteries. No external loads running.
Batteries are 12 month old lead acid - 2 x 12V fully charged- with electrolyte SG ~1.24.
Those readings were with a new Delco. I replaced the original because it displayed same symptoms, and I concluded it had a faulty regulator. This model Delco has an internal regulator.
I have parallel neg and positive cables between the Delco and batteries – in case of loose connections. Clamp meter readings show the cables are OK - low resistance.
I have monitored the voltage difference between the alternator exciter wire – connected to terminal No 2 of the Delco, and to the +ve battery terminal. That difference oscillates from -0.02 to + 0.06V.
That reading from the other, problem free engine’s Delco, is about 0.02V. It delivers a rock steady charge of (approx.) 3A and 27V into the same battery system -immediately after start up.
I’ve started and run the good engine with the instrument cluster from the problem motor- by cross connecting the wiring harnesses at the instrument panel – to check if the fault is in the start system in the cluster– and found no problem.
However, Ive yet to cross connect the harnesses in the engine room to check if the prob is in the wiring harness - between flybridge and engine room.
Presumably connected with this problem is that the gearbox oil pressure gauge display has died. The sender complies with VDO spec ----10-184 ohms.
Cummins have not been able to supply a wiring diagram for this model – and otherwise have not been able to suggests a cause.
The highly fluctuating output should surely help narrow down the cause- eluded me so far. It fluctuates so fast – suggesting – to me at least, that it’s not merely a loose connection.
The high currents are damaging the batteries and I therefore have to conduct tests as fast as possible.
Any help greatly appreciated.
All current goes only to the batteries. No external loads running.
Batteries are 12 month old lead acid - 2 x 12V fully charged- with electrolyte SG ~1.24.
Those readings were with a new Delco. I replaced the original because it displayed same symptoms, and I concluded it had a faulty regulator. This model Delco has an internal regulator.
I have parallel neg and positive cables between the Delco and batteries – in case of loose connections. Clamp meter readings show the cables are OK - low resistance.
I have monitored the voltage difference between the alternator exciter wire – connected to terminal No 2 of the Delco, and to the +ve battery terminal. That difference oscillates from -0.02 to + 0.06V.
That reading from the other, problem free engine’s Delco, is about 0.02V. It delivers a rock steady charge of (approx.) 3A and 27V into the same battery system -immediately after start up.
I’ve started and run the good engine with the instrument cluster from the problem motor- by cross connecting the wiring harnesses at the instrument panel – to check if the fault is in the start system in the cluster– and found no problem.
However, Ive yet to cross connect the harnesses in the engine room to check if the prob is in the wiring harness - between flybridge and engine room.
Presumably connected with this problem is that the gearbox oil pressure gauge display has died. The sender complies with VDO spec ----10-184 ohms.
Cummins have not been able to supply a wiring diagram for this model – and otherwise have not been able to suggests a cause.
The highly fluctuating output should surely help narrow down the cause- eluded me so far. It fluctuates so fast – suggesting – to me at least, that it’s not merely a loose connection.
The high currents are damaging the batteries and I therefore have to conduct tests as fast as possible.
Any help greatly appreciated.