altenator on the fritz???

[1tuffram]

Lately have noticed the volt meter gauge needle will be a needles width below the 14 volt mark and other times a needle width above and sometimes somewhere in between. Normally my gauge has always read about a needle width above 14 volts. When all this is happening no electrical accessories are running. I do not notice the needle to fluctuate while driving or varying the RPMs. If when I start the truck the needle is below 14 volts it stays there the whole time the engine is running. Then the next time the engine is started it may or may not be back to the normal needle width above 14 volts. This appears to be one of those intermittent problems at this point in time, so it may prove difficult to track down. All battery cable connections are clean and tight. All alternator connections are tight. Batteries where replaced a year ago.



I am wondering if its the alternator or voltage regulator starting to give out. Also wondering if it's a bad battery, like maybe a broken plate or something. Don't think it could be one of the grid heaters sticking on cause it is not pulling the volt meter needle down very much (like it does in the winter when the heaters kick on).



I have not noticed any problems YET. I'm just wanting to track this down before it turns into a problem and leaves me stranded. Any thoughts

 

[Dieselnerd]

Unless it continues to operate the way you describe when the weather cools off, normally when we have the kind of heat we've had lately the charging voltage is cut back. If it didn't the batteries would overcharge. Voltage regulators cut voltage when it's hot outside and increase it when it's colder.



This doesn't mean you don't have a problem but it could also be normal operation.



Mine normally is to the right of the center line too but in the recent hot weather it didn't go past the center line of the gauge either.

 

[Ron Bissett]

Originally posted by 1tuffram

Lately have noticed the volt meter gauge needle will be a needles width below the 14 volt mark and other times a needle width above and sometimes somewhere in between. Normally my gauge has always read about a needle width above 14 volts. When all this is happening no electrical accessories are running. I do not notice the needle to fluctuate while driving or varying the RPMs. If when I start the truck the needle is below 14 volts it stays there the whole time the engine is running. Then the next time the engine is started it may or may not be back to the normal needle width above 14 volts. This appears to be one of those intermittent problems at this point in time, so it may prove difficult to track down. All battery cable connections are clean and tight. All alternator connections are tight. Batteries where replaced a year ago.



I am wondering if its the alternator or voltage regulator starting to give out. Also wondering if it's a bad battery, like maybe a broken plate or something. Don't think it could be one of the grid heaters sticking on cause it is not pulling the volt meter needle down very much (like it does in the winter when the heaters kick on).



I have not noticed any problems YET. I'm just wanting to track this down before it turns into a problem and leaves me stranded. Any thoughts

Try a volt meter on it at battery after cleanig of posts watch both meters and see if they match or come close , don't think the guage in truck is a true measure just a way of showing charge no charge any thing above 12 volts is + fourteen is fine + - 2v on guage multy meter at batt should be right on voltage true. Ron in Louisville Ky

 

[fest3er]

Originally posted by 1tuffram

... I am wondering if its the alternator or voltage regulator starting to give out. Also wondering if it's a bad battery, like maybe a broken plate or something. Don't think it could be one of the grid heaters sticking on cause it is not pulling the volt meter needle down very much (like it does in the winter when the heaters kick on). ...

Not sure about the '95; on my '98 the voltage regulator is in the PCM, and I wouldn't expect it to fail. If an intake heater relay is failing, you might notice flickering in the dash lights and headlights at night on coarse roads as a relay bounces against the contact.



The only way to check the batteries is to park the truck for a day or so, then check the voltage of each individual battery. A bad battery should have lower voltage, showing it isn't holding a charge. Even with a bad battery, the voltage should stay up.



Since the dash gauge is driven via messaging from the PCM, the 'fault' would lay between the PCM and the alternator, either in the voltage sensing lead, or the alternator field lead. Check the voltage at the battery while the engine is running; it should be somewhere around 13. 5-14. 5 VDC. If it's higher, I would suspect the connections to the PCM. If it's lower, I might suspect the alternator (a bad diode): this is easily checked with a scope.



That all said, remember that semiconductors can often behave differently when they get hot. If the voltage is remaining at 13. 5-14. 5 VDC with a good load on the electrical system, it's probably normal variation. If the alternator has a bad or flaky diode, it might not be producing enough current when it gets real hot. I had an alternator fail on me driving through DFW area. Cold, it charged just fine. Hot, it wouldn't charge at all. It had a bad diode, losing 1/3 of the output.



Keep an eye on it, but don't worry *too* much. Remember, our mechanical 12Vs don't require much electricity to run. If you're really curious, have a shop scope the alternator in-vehicle *when it's hot*.



Most likely it's just normal variation and is naught to worry over. If your headlights start getting real dim at night, you might start worrying a bit more.



Fest3er

 

[1tuffram]

Thanks guys for the input. I'll check the voltage at the batteries to verify the accuracy of the dash gauge and monitor things as the weather starts to cool. It has been rather warm here latley so maybe it's operating normally.