Alternator Bad?

[95Finder]

I have a radar detector that has a voltage meter on it. Are these accurate. When the Pathfinder is running without the lights on the voltage meter displays 10.1. With the lights on it dips below and flashes low voltage.

[hardwaretoad]

That's way low, dude. Should be reading 13.5 or so. Might be a voltage regulator, or the alternator itself. Might even be something as simple as corroded terminals on your battery or a loose belt.

 

No voltmeter in your dash ? I wouldn't be able to speculate on the accuracy of your combo radar detector/voltmeter... does it sharpen knives too ?

[gacruiser]

Unless your voltmeter is attached directly to the battery, you have no way of knowing if there might be simply a voltage drop at your cigarette lighter plug (I'm assuming that's where you've got it connected).

 

That said, get a cheap VMM at Rat Shak (~$8-10) and connect it to your battery posts. When running engine with lights off, you should see 13.5-15V. If less than 12.8V, you probably have a dying alternator or voltage regulator. With engine off, you should see 12V+ across the terminals. If less than 12V, your battery's either not fully charged, or you have a dead cell.

[88pathoffroad]

Take it to an auto parts store and have them test it for you. Easy and free.

[95Finder]

Replaced the alternator, the system is now running at 13.4 instead of 10.4 like it was with the bad alternator. Before my brake light, battery light and a/t temp light were all lit up, after installing the new alternator all the lights have gone off. Later.

[Precise1]

Hey 95Finder. Glad to read your rotor change went relatively smooth; its the learning curve that gets ya the first time... Next time it's 20 minutes a rotor max. The alternator seems to be the fix, but for a week or two, check the battery output... You should have a steady 12+ volts without the motor running; keep the leads on and watch the meter when its started. If it dips below 8-9V generally means its getting weak (if so check fluid levels/terminal conductivity). Not a problem if it holds 12+ volts generally but could be if you are in cold country. A tired battery can kill an alternator faster than anything, not to mention leave you stuck when its not convenient...

 

Bernard

[95Finder]

Hey 95Finder. Glad to read your rotor change went relatively smooth; its the learning curve that gets ya the first time... Next time it's 20 minutes a rotor max. The alternator seems to be the fix, but for a week or two, check the battery output... You should have a steady 12+ volts without the motor running; keep the leads on and watch the meter when its started. If it dips below 8-9V generally means its getting weak (if so check fluid levels/terminal conductivity). Not a problem if it holds 12+ volts generally but could be if you are in cold country. A tired battery can kill an alternator faster than anything, not to mention leave you stuck when its not convenient...

 

Bernard

Thanks, yeah the rotor change when pretty smooth, I had never done rotors on a 4 wheel drive vehicle before so I wasn't used to taking the hub apart. On my supra you just pull the caliper and the rotor slides off(or you thread screws into both sides tighten them and it slowly works its way off). Wasn't too bad though. The alternator went pretty smooth also except for the rust in my eyes . My battery is brand new so I don't think it should be a problem. I will keep and eye on it though. Thanks for everyones help. Later.