Alternator voltage problem / starting issue

[vthokie]

Hey guys,

Recently I have noticed on my scangauge2 that my voltage has been varying pretty significantly. It used to stay in the range of 13-14 volts and now it spikes up to 15v and almost 16v at times. I'm a little concerned, and I don't really know what is causing it. The other day it hit 17v. It has only done that once, and it even caused my radio to reboot. What could be causing this?

I had my alternator and battery checked at Advance and they said everything was fine. It was also just sitting in a parking lot and I didn't notice much variance on the scangauge2 during the test.

Could my voltage regulator be going bad? If so, is that built into the alternator? Replacing the whole thing might be the easiest solution. I was also wondering if a bad ground could be causing this?

I have also had another interesting thing happen just yesterday. As I turned the key in the ignition, it lost all power, and wouldn't start. This has happened once or twice before since I have had the truck, and it will start if I take the key out and wait about a minute or so... I think maybe my ignition switch might be the cause of this problem.

Could a bad ground cause both of these problems? I'm really not sure what to do at this point, so any advice could help.

Thanks!

 

[Skidmarcx]

In any case you must check ALL your major electrical connections at the battery, alternator, and starter... verify solid grounds... the high voltage indicates a faulty regulator, but perhaps there is a bad ground causing your scan gauge to read incorrectly and resetting your CB...

 

[country]

Bump!

i hope there are some still talking about this problem. i have a '90 pickup that will be fine for several days after charging battery, then when i turn the key it just clicks, maybe tries to turn over. dead truck. battery is new, cable ends new, everything is clean. this happens if the battery drops below 12.5 at rest. running at 1000 rpm i have 14.7 volts at battery yet it keeps discharging. i had battery and alternator checked and the guy said both were fine and he also said there was no drain on bat. i don't how he could tell that.
what can this be? relay going off/on? winter is almost here!! thanks, john

 

[19963.4lsr5]

12.0 should start your engine is starter contacts, and all connections are good clean and tight.

12.5v at rest is a normal state of charge after a day or two.

When the contacts start going bad it will work and then it won't and then it will work again. Totally a random which makes you think something you did fixed it till it happens again.


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[hyken]

i hope there are some still talking about this problem. i have a '90 pickup that will be fine for several days after charging battery, then when i turn the key it just clicks, maybe tries to turn over. dead truck. battery is new, cable ends new, everything is clean. this happens if the battery drops below 12.5 at rest. running at 1000 rpm i have 14.7 volts at battery yet it keeps discharging. i had battery and alternator checked and the guy said both were fine and he also said there was no drain on bat. i don't how he could tell that.
what can this be? relay going off/on? winter is almost here!! thanks, john

Hey man I just did a starter swap in my 4runner that had the same exact problem. My voltage varied wildly when trying to start it. Most people think it's the contacts in the solenoid, but when it clicks and nothing happens, it's actually the plunger inside the starter that won't engage the reduction gear to the flywheel. Have Advance check your starter too.

 

[nevada]

i hope there are some still talking about this problem. i have a '90 pickup that will be fine for several days after charging battery, then when i turn the key it just clicks, maybe tries to turn over. dead truck. battery is new, cable ends new, everything is clean. this happens if the battery drops below 12.5 at rest. running at 1000 rpm i have 14.7 volts at battery yet it keeps discharging. i had battery and alternator checked and the guy said both were fine and he also said there was no drain on bat. i don't how he could tell that.
what can this be? relay going off/on? winter is almost here!! thanks, john

you'll have to get a good multi-meter and start checking circuits. sounds like there is a draw in the system somewhere.

 

[Ricktuk]

i hope there are some still talking about this problem. i have a '90 pickup that will be fine for several days after charging battery, then when i turn the key it just clicks, maybe tries to turn over. dead truck. battery is new, cable ends new, everything is clean. this happens if the battery drops below 12.5 at rest. running at 1000 rpm i have 14.7 volts at battery yet it keeps discharging. i had battery and alternator checked and the guy said both were fine and he also said there was no drain on bat. i don't how he could tell that.
what can this be? relay going off/on? winter is almost here!! thanks, john

employee having the same problem with his. after about the 3 rd time checking the alternator finds out that it isnt quite keeping up when everything is going truck isnt running fast. So if he is in traffic going slow and has lights and AC going his battery is slowly being drained. check your belts and connections at the battery and alternator if they are good change it. I lucked into a "used" Toyo on Amazon. looked like someone had bought it and returned it . bolts were still in plastic bags. got it for 30 bucks

 

[curryT4R]

employee having the same problem with his. after about the 3 rd time checking the alternator finds out that it isnt quite keeping up when everything is going truck isnt running fast. So if he is in traffic going slow and has lights and AC going his battery is slowly being drained. check your belts and connections at the battery and alternator if they are good change it. I lucked into a "used" Toyo on Amazon. looked like someone had bought it and returned it . bolts were still in plastic bags. got it for 30 bucks

Also check the throttle body is clean of carbon. I had a GX 470 that I thought needed an alternator, but turns out the throttle body had lots of carbon buildup causing a low idle, so the engine wasn't spinning fast enough to charge the battery enough.

 

[19963.4lsr5]

You should be at at least 13.0v in gear at idle with everything on. Headlights fan and AC on and your foot on the brake. Although some will say that 12.7 is ok in that condition because how infrequent it is.

12.5v is a at rest normal battery voltage at the posts after sitting 12-24 hours


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[nevada]

You should be at at least 13.0v in gear at idle with everything on. Headlights fan and AC on and your foot on the brake. Although some will say that 12.7 is ok in that condition because how infrequent it is.

12.5v is a at rest normal battery voltage at the posts after sitting 12-24 hours


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I would consider 12.5 to be low. I want them 12.6 or higher. preferably 12.7. there is very little margin in batteries. 12.0 is DEEPLY discharged, at 12.4 it starts to sulfate.

 

[19963.4lsr5]

I would consider 12.5 to be low. I want them 12.6 or higher. preferably 12.7. there is very little margin in batteries. 12.0 is DEEPLY discharged, at 12.4 it starts to sulfate.

I keep a voltmeter in the cig lighters on all my vehicles. I see 12.5 in all of them. Including my Cummins with dual batteries. If this is the first time you ever looked at your battery voltage it's what I normally see in my 2002 Saturn, two 97 4Runners, and my 94 Ram with the diesel. My 4Runner batteries are 1 year old and act the same as my 6 year old batteries (2 of them) in my Ram or the 5 year old battery in my Saturn. My Saturn in the dead of winter with 12v showing up on the volt meter before I turn on the ignition and still starts it just fine when it's 5f outside. (Ignition on voltage drops to around 11.5v)

The battery will stay at 12.7 after a charge with no cables hooked to it if the battery top is clean, and it has no internal damage) Put a voltmeter lead on the plus post and probe around the battery top with the other probe. You can see up to 10v is the battery has vented and acid (and most do eventually) on to the battery top. (White or gray film)

connected to the vehicle it will not stay there. Plus in the winter the at rest voltage will be closer to 12.0-12.3v which will make one think the battery is dead. But the cold acid lowers the effective voltage and capacity.

Just giving you my experience. Yours may vary.

Edit: the 12.7 voltage for a fully charged battery aka 100% is with a electrolyte temp of 80 degrees. A good rule of thumb is for every 10 degrees f above 80 you add .1v to the 12.7 and that is your 100% voltage reading and for every 10 degrees below 80 you subtract .1v from 12.7. So a battery that's 30 degrees F has a 100% charge post voltage of 12.2v and that same battery with a temp of 120 degrees F will have a 100% charge post voltage of 13.1v


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