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Decaying voltage

tracy

Well Known Member
Friend
Voltage used to show 14 -14.1 volts, but now is showing 13.8 volts 9 years and 700 hrs later. Would you expect this to be alternator getting tired or something else? Would I need to correct this at this time? Denso 40amp.
 
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Many Possibilities at this point

It certainly could be a current drop, do you have an ammeter to watch that? Depending where an ammeter sits you can make conclusions about whether the battery is participating in the problem, or if the regulator is suspect. Determining if it is the alternator itself can be done on a bench check at your local car parts supply.

It could be a voltage drop by resistance either on the field side or supply side (yikes) including grounds.

Start checking voltages in different places, then start isolating variables with some known good values.
 
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I do have an amp meter between the alt and battery, or position a, when referring to dynon shunt diagram. There is an increase in amps from 0 or1 to 3 or 4 now. Maybe it is battery getting week. It still starts fine though.
 
Nice, if you see an unexplained increase in load then you probably have a battery that is beginning to internally short (normal process of battery age). Do a load check on the battery. A start isn't always the best way to load check.
 
Thanks, I’ll do that. The battery is only a year old, appex12220, and i switched to it because it starts stronger than the odyssey and is about 1/3 the cost.
 
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Premature failure happens, but obviously the age of the battery may force the troubleshooting onwards. There is where the 'known good' part of isolating variables comes in.
 
battery health should not impact the alternators ability to hold the set voltage, unless it is so bad that it is maxing out the alternators output.

Possibly a bad VR in that Alternator or too much resistance on the line that is measuring the bus voltage.
 
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