Corrosion and Volt Drop issues.

This was the ground wire to the starboard alternator. The Alternator Does Not ground via the frame on this model as most marine alternators have an external ground. 
We had both our alternators overhauled by my friends at Johnson's Electric in Carrollton Georgia. We had used their services for many years and they are trusted and reliable. The Volvo Alternators did not have a problem but were 30 years old and I felt they needed a good look see at all there parts. They ran about 10 hours and the starboard engine showed low voltage on the gauge. I checked and the voltage was barely above 12.4 Volts

I wish my picture was better but the wire is green except where it overheated . All this was covered by the cap and insulation. Replacing the wire and connector fixed the problem and now the alternator charges fine. I wonder how many alternators are replaced because of problems in the circuit. 



This is a relay test for volt drop across the circuit. The starter relay is not clicking and there fore the starter doesn't work.

Good relay with bad circuit due to corrosion.  this section of the circuit going to relay is good. Look up stream for problem.

Using this tester is easy. The push button loads the circuit with a 100 ohm load


Understanding the circuit design allows you to quickly diagnose the problem.

Up on the dash at the switch now I find a circuit that is showing 13 Volts. When it should read near zero. The battery charger is on at this time. 



One terminal is corroded causing the volt drop and the starter not to operate. The terminal at the 9 O'Clock position is the culprit.




This is the terminal connection that has the offending connection. I by passed the connector and ran a new wire on this 30 year old boat. Because I knew how to test for volt drop I did not have to replace a bunch of good parts to fix the problem.
Here are some resources to help. https://autoteacher.net/Electronic_Q3HM.html  or you can google Volt Drop Test



Comments

  1. Jeff CurtisMarch 29, 2015 at 1:01 PM

    Volt drops, volt drops, volt drops... How many technicians yet need to learn this skill?

    ReplyDelete

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