Alternator going bad?

[CMGRover]

Just wondering if anyone is familiar with the signs of an alternator going bad. Past few months on occasion I've smelled a slight "electrical burn" smell after pulling the LR3 in the garage and it seems slower to crank over- the battery is good to my knowledge- like maybe it's not getting charged properly? No faults.

Thanks!

 

[Disco Mike]

This is not rocket science, go to a local parts store and have them perform a free full load charging system test, voltage should be between 13.6 and 14.4 volts.

 

[CMGRover]

Did that about 1.5 months ago, everything tested out ok but I don't have the greatest faith in those types of tests.

 

[Houm_WA]

My alternator let me know it was on its way out by howling at me. Don't know if that always happens though...

 

[PhyrraM]

Mine failed with a short in one of the rectifiers. This did cause a burned electrical smell as the battery discharged through the alternator. Smoke and a very heavy acrid smell at the conclusion.

The ECU controls the alternators output, so sometimes a traditional charging system test doesn't give reliable information.

Most pending alternator (and battery) failures are accompanied by random error messages and warning lights from the various systems. Particularly transmission related ones.

 

[bbyer]

I beg to differ ....

I noticed a comment to the effect that it should be easy to test for the proper operation of the alternator. Yes, it should be easy, but at least for me, it is not.

I find that there is something different about the design of the regulator located within the alternator and that it can fail in a manner that is not obvious to the normal alternator shop testing procedures.

About the only thought I have is that it has something to do with the interaction of the regulator with the engine computer. In the case of our 3, it was one of the first vehicles to use what Denso or Land Rover calls a Smart Regulator, (and I call dumb).

The regulator gets its instructions from the engine computer rather than the battery. The instructions are transmitted in the form of a digital like Pulse Width Modulated, (PWM), signal rather than just simple battery voltage per regulators of the previous more common design and what we are used to. The reasoning behind the change relates to furthering fuel economy.

Since this is such a "smart regulator" if appears to also have a fail safe mode where it can default to about 13.3 volts, (rather than just quitting), and also allows a certain amount of current to be generated. This amount appears to be enough to run the ignition, radio headlights etc, and provide a bit of a charge to the battery as well. The battery however tends to be last on the list apparently due to unintended software glitches - probably for the same reason the battery never gets fully charged even when all is well. As the battery is last on the list, I think that is why the alternator light on the dash will sometime come on and then go off.

The bottom line to all this magic is that while the alternator can test OK by using the normal alternator shop techniques that have worked since the fifties, those techniques do not necessarily yield correct results on these new PWM regulator alternators.

Ford is now using these same style regulators within the alternators on some of their newer vehicles and recommends a testing procedure that they call PCM/RC where PCM means Powertrain Control Module, similar to ECM per Land Rover.

About the middle of the album per the link below, there are five files related to the alternator and the regulator that may be of interest.

http://bit.ly/1hrIQm5

 

[nivekau]

My alternator let me know it was on its way out by howling at me. Don't know if that always happens though...

Same happened to me, plus an electrical burning smell.

I read on another thread a report about one that caught fire!

As for slow starting I'd be checking the battery first. The fact that a battery was fine 1.5 months ago means nothing. They can fail very quickly (mine has done that as well, about a year before the alternator failed).

 

[goinsurfin]

A year ago i had the similar symptoms, burning smell + light up dash icons. After replacing the alternator, I ended up replacing the battery too because of the major draw from the alternator. Fortunately, the battery was replaced under warranty.

 

[Team Jeff]

The symptoms with my alternator failure were;

Low volume restriction (HSE) for 10-15 min in the am

Overhead HID lights (8" visionx) were difficult to light

Slow cranking

I may have had a slight bit of noise from it, but the belt was due to be changed & could have been causing the sound I heard, or masking some sounds the alternator was producing.

No burning smell at all.

bbyer - thank you for the accurate & detailed information. It's what I've come to expect and appreciate about your posts!

 

[rhearrel]

Just had mine replaced this week. Mine had a growling howling sound and I had a faint smell of burning electrical under the hood.