Battery Light flickering

I got this truck used and its at 260k. Runs great but I have been servicing everything I can on it to make it last. I notice that when I was driving at night the battery light the battery light would come on and flicker faintly from time to time. Normally at higher speeds above 55mph. I could tell the bearings in the pulleys were worn so I replaced all of the pulleys (2) #1's, #2 and the tensioner pulley along with the factory new toyota belt. Still making the battery light flicker and maybe now it is worse. Which is weird. Any ideas?

 

I'm betting you have a loose belt or the voltage regulator in the alternator is failing. Prolly the voltage regulator.

 

I hope it not too big of a pain, if its a regulator what would you guys suggest for a replacement? Toyota or any good aftermarket brand?

 

I will have to go out and look at the wiring coming from the alt tomorrow if I get a chance with the rains we have been having and see if anything is loose.

 

Do you know how to use a multi meter?

Can you check the output voltage?

 

I do.

 

I will check the volts and post back what I find out here. Thanks guys might be a day or so.

 

The regulator is inside of the alternator. At 260K chances are pretty good the brushes are worn out and probably have cut deep grooves in the field rotor. Yes your best bet is a new alt.

 

People have had good success with Denso alternators from Rockauto.

DO NOT, DO NOT, DO NOT buy an alternator from Auto Zone, O'reilly, etc.

Also, there is a wire in the connector that plugs into the alternator that corrodes and makes the light come on, even though the alternator is working perfectly. I think it's a white wire that corrodes inside the insulation about 1" up from the connector.

 

Thanks guys I will check this out! Love this site.

 

Sorry to hear about your troubles.....lets see if we here at TW can help!

Please let us know what the output of the alternator is when you do test the battery under load. Can you also share any information about the battery? Age, wet/gel ect.

 

Updating
Battery terminals cleaned
Battery cables look to be in good shape
Cleaned ends of terminals
Battery reads 12.53v before start
Battery after start 14.31v
Battery under full load @2000rpm 14.17v
Battery at full load idle @5mins 11.95v low idle when higher idle 12.20v

 

Battery installed is a no brand no markings other than date code sold of June 19' but it does not fit the battery tray all the way and there is space on both sides about 2-3" on left and 2" on the right side.

 

before we attach the issues of the battery size lets make sure the alternator is working...

How can I tell if the diodes are bad in a voltage regulator?

A quick way to check is by using a multimeter. Touch the big post on the alternator (the positive terminal post on the alternator) with the red lead of the multimeter, and touch the other lead on the alternator case. With the multimeter set to measure resistance, it should measure more than 550 ohms if the alternator diode is any good. Make sure when you do it that the battery is disconnected to prevent any electrical shorts or shocks

 

I was just into a Taco alternator. Replaced both bearings and the brushes. The regulator is a soldered in piece of a rear assy. and not a DIY IMHO. Likely your brushes are bad as well as the bearings. Maybe get a new/rebuilt from Rock Auto, or if you are really hard core you could do the bearings and brushes. Beware I bent the pulley on mine and it a $35+- OEM part or a $25ish aftermarket.

 

Looking at the alternator you can tell its factory and with 260k on it I am leaning towards its just worn out. Called local Autozone spoke with a trusted guy I know there and he said they could check the alternator with the machine they have while its still in the truck. But he told me like others here have said, its just probably worn out. Ill keep you guys posted. Thanks again for the support!

 

Those machines that check the alternator should not be trusted. If you have an intermittent bad voltage relay, it will read that the alternator is good.

 

Okay I see. Glad to hear this. I did notice that the battery while in idle at full load the voltage kept dropping every time the trucks idle would cycle through. If that helps. I just have to find out which alternator goes into the truck. Looks like there are 4 different part numbers for Denso brands.

 

Called Toyota with Vin and its the 100 amp model non-towing

 

I had the intermittent light flashing and it was the main charge wire connection was loose at the alternator. check that too, it may also be corroded.
I forgot to tighten it when I did head gaskets job.