tacoma 2010 alternator diodes fail.

Hi guys, I'm a new member.

I have a 2010 Tacoma pre runner sr5.

Yesterday morning the truck did not start.It wouldn't even click.I checked the battery and had 12.6v I jump started it and auto zone checked it.They said the alternator rectifier failed.I've read

somewhere that batteries even though they show good voltage can be bad....any comments.

thanks in advance. airframeabe

 

It can read 12 VDC and up with no load, but when when you try to start it it drops to near zero and you get nothing. Diodes do fail, get a new or rebuilt OEM Alternator and call it good. These diodes can be replaced if you are good at disassembly of an alternator.

 

I think I posted in the wrong forum. but anyway,i installed a new batt and the diode failure went away. I think the old batt triggered the diode fail.the old batt was three years old this month.everything is ok now.

 

I've seen batteries read 12.7V and flunk a load test. The Open Circuit Voltage test is meaningless unless you are reading low.

The only real test is a load test.

 

If you truely do have a shorted diode the new battery will also fail eventually. Did you ever get a Battery Light on the dash? Battery Light on with the ignition on running indicates a shorted Negative Diode. Battery light on with the ignition off ( key removed ) indicates a shorted positive diode.

 

I would not hesitate to take the car to an alternator/starter shop to test the charging system. Most will not charge for a quick check. If you have a voltmeter, you can perform a simple test; look it up on youtube. Look up a mom/pop shop - the messier the shop the better!

 

I have had several situations were an auto parts store informed me my charging system was to blame, only to replace the battery and be just fine.
Changing a battery is quick and easy. I would change the battery, drive it for a day, take it back and have them check it again.

 

That's what I did.I replaced the batt and went back to autozone to have it checked.The alt diode failure went away.It's weird that the old batt triggered the alt diode failure.I'm glad I didn't have to replace the alternator.Btw the old batt was three years old this month,