Alternator problems?

[Bob77064]

The gauge in my truck has always shown 14 volts, for a few weeks now it has gone down to 13 and up to 15 several times. Does this indicate a problem with the alternator or voltage regulator?

 

[sam5570]

depending on the age of your truck the regulater is probably built inside the alternator what i would do is chack the alternator charging from the battery with a tester see if it jumps from 13 to 15 volts if it stays around 14 then you have a guage problem witch is on a printed circut and the whole panel has to be replaced more than likly just be sure and do the basic checks first check battery and conections on the alternater hope this helps

 

[Soundguy]

deffinately check with a multi meter.. set in truck and probe cig lighter and do it at idle and revved.

if it drops below 13.8 at idle.. or goes over 15 revved.. time for a checksee.

 

[murphy1244]

deffinately check with a multi meter.. set in truck and probe cig lighter and do it at idle and revved.

if it drops below 13.8 at idle.. or goes over 15 revved.. time for a checksee.

SG, On a side note. If your ammeter gage jumps from center to charge back and forth, is that a bad regulator? Thanks.

 

[Bob77064]

Thanks for the help guys.

 

[crashz]

I'm no expert, but a jumping ammeter would probably indicate a loose connection or short of some kind I would think.

BTW - My 2004 GMC had alternator troubles at ~ 150K miles and I changed the alternator. Had some charging issues with the replacement and let it go becuase it wasn't setting any messages or codes. I ended up frying the Body Control Modual. Which then lead to a whole mess of electrical gremlins. So my point is to get that straighten out ASAP.

 

[Bob77064]

My truck is a 2007 Tundra with 119k.

 

[Soundguy]

SG, On a side note. If your ammeter gage jumps from center to charge back and forth, is that a bad regulator? Thanks.

if this is on a generator based system, i'd say it could be worn brushes, weak springs or tall mica.. or a real cruddy vreg field circuit, perhaps with an open bias resistor.

need to know the application before going further with that thought.

 

[Soundguy]

I'm no expert, but a jumping ammeter would probably indicate a loose connection or short of some kind I would think.

.

short? that failure mode not coming to mind unless I also see smoke..

 

[puckgrinder85]

What year vehicle? Reason I ask is they started monitoring load on the electrical system, if there is no load then they turn the duty cycle of the alternator way down to conserve fuel. It may just be something you noticed. We dont test alternators with a DVOM, you need to load it to get a real test.

 

[Grumpy Old Man]

Keep it simple ,You have a 5 year old battery clean the terminals and take it to most any auto parts store they do free load checks . maybe it's just time for a new one !

 

[schmism]

just replaced the alternator in my E350 van. It was showing a half a battery light on the dash... started to come on every now and then, and over a period of 4 days got progessivly worse. (stayed on more of the time)

I watched the voltage through my scangaugeII. when the light wasnt on 14v... when it was on, 12-10 volts. I looked a local one but the parts places wanted the same price for a rebuilt china one as a i could get a rebuilt bocshe online. so i went that way. bosche one at the local parts places were 2x-3x as much as online.

 

[Soundguy]

What year vehicle? Reason I ask is they started monitoring load on the electrical system, if there is no load then they turn the duty cycle of the alternator way down to conserve fuel. It may just be something you noticed. We dont test alternators with a DVOM, you need to load it to get a real test.

an alternator with a regulator is already doing this.

when current demand is high, the alt vreg changes charge rate to keep system voltage in range.

this is NOTHING new...

 

[puckgrinder85]

Jeff Dunham - Peanut - "NYEWM" - YouTube



New(er) cars and some models are regulated externally by the PCM, which is why i asked for a model/ year as there are tons of them out there. The PCM monitors the loads and keeps fuel consumption and emissions in check, big brother doesnt want anymore power out of that engine that needs to be drawn.

 

[puckgrinder85]

My truck is a 2007 Tundra with 119k.

Original battery? Thats getting over the hill for a battery. Most last 5-7 years.

Really need to load test both to get an idea. Problems with charging generally dont jump out with a voltmeter unless its pretty obvious.

 

[Soundguy]

Original battery? Thats getting over the hill for a battery. Most last 5-7 years.

Really need to load test both to get an idea. Problems with charging generally dont jump out with a voltmeter unless its pretty obvious.

agreed.

I like to look at an ammeter as well. could be cells going bad making higher draw.. etc..

 

[murphy1244]

if this is on a generator based system, i'd say it could be worn brushes, weak springs or tall mica.. or a real cruddy vreg field circuit, perhaps with an open bias resistor.

need to know the application before going further with that thought.

MF 135 Altenator. 1967

 

[Soundguy]

external vreg?

 

[murphy1244]

external vreg?

Yes it is

 

[Soundguy]

i'd check that out.. make sure it has a good ground ref.. pry the can off and look at the contacts..