I recently replaced my M25 alternator mounting bracket from the original to the universal modification. In the process all the wiring from the alternator got broken. I have it back together except for one wire off the alternator. I have the original 1984 alternator with the voltage regulator attached to the backside of the the alternator and clearly visible. There is a thin yellow wire coming out of the regulator which I believe is the voltage sensing wire. The wiring diagram for the M25 manual shows a wire coming off the alternator and attached to a purple wire on the wiring block next to the engine. It seems obvious that these should be connected as I have the yellow off the regulator and a loose purple on the wiring block. Without the wires connected and the engine running I am showing very close to 15 volts on the voltmeter at the starting panel which I think is the max factory setting for the alternator and an obvious overcharging condition for the batteries as it does not move down. I am hoping a C-30 owner of either a 84' or 85' with the original motorola alternator can verify that these yellow and purple wires should be connected...Thanks for any help Wayne owner of Steadfast hull #3701
1984 C-30 alternator voltage sensing wire
- Thread starter windyjazz
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We have 1984 hull #3518 with the original alternator. The purple is connected to the yellow
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Thanks Stu
From your drawings it looks to me like both the red and the yellow should be connected to the purple #6 which is basically the ignition key. I know you replaced both the alternator and the regulator with a external regulator and after searching through some threads found that your original alternator was connected to something called Automac which somehow bumped up the charging current. The red and yellow wires seem to be excitation and sensing imputs for the attached internal regulator. I'm thinking that the red was attached to the field terminal of the alternator below the POS + output terminal and the purple was tapped there and attached to the quick disconnect on the yellow? I'm not sure which was which but I am also not sure it matters since both need to be looking at the battery terminals which would have been purple #6 on the terminal block next to the engine. Just curious on your cockpit panel do you have a key on, push glow plug, and pull starter switch and a pull kill handle? Again thanks for the reply and drawings and all your excellent postings on this site. Wayne
Wayne, you're very welcome. Key on, push glow plug, separate push starter buttons, kill pull handle to the stop lever on the starboard forward side of the engine.
Thanks rb so much for pic
I see everthing on your pic that I have.... the yellow quick disconnect attached to purple, reddish /orange terminal wire on alternator right sidre pic going straight into wire collector (tac tap), black ground on alternator terminal grounded to engine block. The positive alternator output heavy orange going into wiring harness on left side of pic. Below that should be another terminal on the alternator which has a red wire coming off the regulator attached and my suspision is that the purple wire is also connected to that terminal before goining back in to the black wire collector tube. Please fallow that purple wire from the yellow quick disconnect and tell me if I am correct? Also very curious does your cockpit engine panel have a key on, glow plug push on, engine start pull on, and pull handle kill switch? My panel also has tach, fuel, temp, voltmeter, engine hrs. Thanks so much for this further help!!! Wayne
I would characterize our key switch as "Off-Run-Start". Vertical is "Off". A clockwise turn to roughly one o'clock is "Run". At that position, power is enabled to feed the glowplug toggle switch (the engine is not yet starting) and the starting buzzer is sounding. The glowplug toggle is a momentary switch that must be held down to "make". Heat up the glowplugs as long as you want, then release toggle. Next, turn the ignition key switch one more notch further clockwise, to two o'clock, and it supplies power to the starter solenoid (engine cranks). Release key (and it spring returns back to the one o'clock position), the starter stops, and the engine stays running. Engine kill is a T-handle cable. No push-button start. Five gauges: Fuel, Temp, Tach, Volts, Hours.
Rob
Rob
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