I'm working on a 1980 Catalina 38. The boat is in rough shape. We been working mostly on getting the motor to start reliably. After a new filter head, ignition switch and a relay, we have that task completed. Now we are replacing the gauges. I swapped the ammeter for a volt meter, so I need the rewire the alternator output. Upon removing the alternator I discovered that the output cable was not connected to the output post, it was instead connected to what I think is the voltage regulator sense post. I'm not sure the ignition exciter lead was even connected, it fell out of the crimp connection at some point.
On the way home I stopped by 2 automotive stores to have it tested. The first one refused to test it because it was off of a boat. I probably test a thousand alternators when I worked at an automotive parts house and I never turned anyone away without at least trying. The second one tried but he seemed very confused and even forgot to connect the output lead at first. I think the boat was charging last year.
After cleaning the alternator up I've made a few observations.
1. It has an extra diode plate connected to the output. After a little research it seems to be called a isolation diode.
2. I don't see a stator output. No wonder the tach doesn't work.
3. I believe the post with red wire is connected to the output of the rectifier. If the is in fact true then the pervious ower bypassed the isolation diodes by connecting the output cable to this stud.
Why use an isolation diode? It seems like it would lower the out voltage and do little more.
On the way home I stopped by 2 automotive stores to have it tested. The first one refused to test it because it was off of a boat. I probably test a thousand alternators when I worked at an automotive parts house and I never turned anyone away without at least trying. The second one tried but he seemed very confused and even forgot to connect the output lead at first. I think the boat was charging last year.
After cleaning the alternator up I've made a few observations.
1. It has an extra diode plate connected to the output. After a little research it seems to be called a isolation diode.
2. I don't see a stator output. No wonder the tach doesn't work.
3. I believe the post with red wire is connected to the output of the rectifier. If the is in fact true then the pervious ower bypassed the isolation diodes by connecting the output cable to this stud.
Why use an isolation diode? It seems like it would lower the out voltage and do little more.
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