Alternator Woes
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liberator221 (11-06-2022)
11-06-2022, 09:14 PM
#22
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Thread Starter
Engs are 468's with 10.25:1 compression. It takes some juice to spin them. Don't see any corrosion at any of the connections I've seen so far. Haven't removed the batt switch yet. May be something going on there.
The bad alt ground theory made sense. If the alt ground was a couple of volts above batt ground, that would explain things. However I'm pretty sure I can rule out the bad alt ground theory now.
Still having trouble understanding how I can read 16.7V at the SENSE terminal of verified good alternator with a good ground and why jumpering from alt output to pos batt terminal helps lower the alt output from 16.7V down to 15V.
Next steps are to install jumper in parallel with the remaining batt cables (one at a time) and batt switch.
BTW, thx for the assistance!!
The bad alt ground theory made sense. If the alt ground was a couple of volts above batt ground, that would explain things. However I'm pretty sure I can rule out the bad alt ground theory now.
Still having trouble understanding how I can read 16.7V at the SENSE terminal of verified good alternator with a good ground and why jumpering from alt output to pos batt terminal helps lower the alt output from 16.7V down to 15V.
Next steps are to install jumper in parallel with the remaining batt cables (one at a time) and batt switch.
BTW, thx for the assistance!!
11-06-2022, 11:20 PM
#23
Registered
Thread Starter
Found this.
https://www.thehulltruth.com/boating...rcharging.html
See post #4 saying some Mondo VRs have a dummy SENSE connection and the voltage is sensed on the EXCITE terminal. I haven't checked the EXCITE terminal when eng is at higher RPMs.
If the EXCITE voltage is coming from a source that has higher current draw at higher rpm, that might be the issue. I know the MSD box pulls significantly more current at higher RPMs. So if EXCITE is tapped into that wire....humm.
Edit: Just remembered that during bench testing of the voltage regulator, I connected EXCITE terminal to a variable bench power supply and set to 12V. SENSE was connected to another variable power supply and as I sweep voltage from 12V to 15V, the brushes would de-energize after SENSE terminal went above 14.6V. Doesn't sound like I have a dummy SENSE terminal on my voltage regulator.
https://www.thehulltruth.com/boating...rcharging.html
See post #4 saying some Mondo VRs have a dummy SENSE connection and the voltage is sensed on the EXCITE terminal. I haven't checked the EXCITE terminal when eng is at higher RPMs.
If the EXCITE voltage is coming from a source that has higher current draw at higher rpm, that might be the issue. I know the MSD box pulls significantly more current at higher RPMs. So if EXCITE is tapped into that wire....humm.
Edit: Just remembered that during bench testing of the voltage regulator, I connected EXCITE terminal to a variable bench power supply and set to 12V. SENSE was connected to another variable power supply and as I sweep voltage from 12V to 15V, the brushes would de-energize after SENSE terminal went above 14.6V. Doesn't sound like I have a dummy SENSE terminal on my voltage regulator.
Last edited by zz28zz; 11-07-2022 at 12:12 AM.
12-05-2022, 10:16 PM
#24
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Thread Starter
A brief follow-up. Made a new jumper with correct terminals and 10ga wire. (Still have old additional jumper installed between alt output and starter solenoid). Installed new jumper between starter solenoid and batt switch. Voltage dropped from 16.7V to 16.3V @3k rpm. Removed new jumper and re-connected it between batt switch and batt, no change. Disconnected cable terminals at batt switch and bolted them together bypassing switch, no change. Re-measured alt ground post to batt neg post and got 30mV at 3k rpm. Re-checked batt ground at block, all good. No corrosion seen anywhere.
Decided to winterize and pick this back up next season. May try swapping the alternators between engs. The port side is the orig old school style with adj voltage regulator.
Decided to winterize and pick this back up next season. May try swapping the alternators between engs. The port side is the orig old school style with adj voltage regulator.
