Charging system is weird

[16Pilot]

When I am at idle my lights are dim. When I get into it a little the lights get brighter. Could this be the battery? or would it be more on the alternator going bad?

 

[KaGee]

Re: Charging system is weird

Somewhat normal. What other loads do you have running on the system at the same time? What does the voltage read at the battery with the engine off? Engine running? Engine reved? If you ever noticed your car sometines does the same thing, normally with a load of accessories turned on.<br /><br />I would have the batteries checked out at Auto Zone to be sure.

 

[marlinempress]

Re: Charging system is weird

If you have a good battery that's big enough, you shouldn't get much dimming, but if your battery is small or is losing it's ability to charge, at low rpms your lights will be getting some straight alternator juice of which most is used by the ignition system, hence the dimming and fluctuation. Alternators aren't real efficient until about 2000 rpm or so.

 

[Don S]

Re: Charging system is weird

It could be the battery, sounds like you're alternator is working, they don't put out much amperage at idle. What is your battery voltage before you start the engine, and at idle. Do you get around 14.5 volts when at about 2000 to 2500 rpm for a few minutes.<br />You may also have a dirty, corroded connection somewhere in the power to the instrument panel. This would cause the light to be a lot dimmer at idle than normally seen.

 

[Boatist]

Re: Charging system is weird

Battery voltage is 12.6 volts with no load. The alternator output is 13.8 volts to 14.8 volts, that is a big jump and you should see it. <br /><br />You can check your alternator belt and make sure it is tight. What is your adle RPMS?<br /><br />With no load your battery voltage should not drop below 12.6 volts, but if your running a blower and big lights and idleing around 600 rpms you are going to see the change in voltage. A small change in voltage will make a big change in light intensity.<br /><br />As DON said what in your voltage before you crank your engine. 12.6 is normal with no load. If it low check all your battery connections, ground and positive side. Check your battery water level and charge your battery all the way up with a good automatic charger. With the engine running at least 1500 rpms and no load it should be at least 13.8 volts. If it is low with the with the engine running at 1500 then check the alternator belt and see if it is worn on the sides. With engine stopped try and turn the alternator both ways it should take some effort. Make sure the belt is tight. Understand also if your battery has not been charged all winter it will likely take several hours of running for the battery to fully charge that is why I suggest you charge with a good automatic battery charger first. If it charges up and your battery charger output should drop to near zero amps.<br /><br />Now with the engine running at 1500 rpms or more and light load you should get 13.8 volts or more. Running big lights, blower, bilge pumps, live well pumps, big stereo all may load it to less than 13.8 volts. <br /><br />If the output voltage is still low running at least 1500 rpms with a light load then you need to check the alternator. You can take it in and have it tested or check it your self. Check the brushes, diode block, regulator, and diode triode if it has one. Also can check the field winding and stator but they rarely fail.