Battery Light On Dash.. Alternator & Battery Test Good

Re: Battery Light On Dash.. Alternator & Battery Test Good

none77 said:

Hi,

Red Battery Light Symbol is showing on my dash. Battery is draining, and I could smell something under hood that I associate with burning electronics smell.


I assumed this was a bad alternator after reading multiple posts on this forum. I removed the alternator and took it to autozone for testing. It passes the test. The guy at autozone didn't really inspire confidence. I take it to O'riellys and have it tested. This guy is better and runs it three times to see if it consistently passes the test.

While I'm removing the alternator, I check all pulley and accessories associated with secondary belt. I also look for any thing that looks shorted, and try to find source of burning smell. I checked ground straps, examined all wires that are visible.

Everything looks good. I re-install original alternator & charge battery. Red Battery Light is still on. Alternator output is 13.6 or 13.7. I went to Autozone and had Battery and Alternator tested on car, and according to Autozone Specs everything passes. No burning smell, and Range Rover drives great except Battery Light on Dash.

I'm open to ideas. Has anyone had any similar experience?

Please advise.

Thanks in Advance,

LL

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The battery with the car off should be 12.5-8 anything below that you're on borrowed time. With the car running you should be seeing ideally 14.7, though even my rig with a new alternator only puts out a constant 13.9 which must be where the voltage regulator is capping the charge. 13.6-7 is low though. Alternators are so cheap after core charge you should have just forgone all the testing and just replaced it IMO. If you have access to an oscilloscope it is helpful to put that on with the car running and seeing what exactly the alternator is doing. Multi meters and the digital testing equipment in those places don't refresh quick enough to spot quick volt spikes or drops but if you log a a minute or two with a scope it'll tell the story. I never had the battery light just remain on as an issue, but for a while I was having all sort of random faults, turned out my alternator was spiking up to 17v intermittently causing various systems to just shut down.

Also check all your battery wiring, grounds etc.

mylife1903 said:

Lou, i have also alternator problem now
I am in trouble with overcharging, i checked the battery connections from alternatir and saw 15.6
but I didn’t battery light.

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replace the alternator asap... likely a failing voltage regulator.

Re: Battery Light On Dash.. Alternator & Battery Test Good

I'm still trying to determine why my alternator is charging at 13.7 on the car. Is the voltage regulator controlled by ECM on 2006 RRSC?


I agree that Autozone doesn't specialize in European or Premium cars. The alternator on my RRSC looked like a Denso Product. I assumed that it was common enough that local auto parts stores could test it. I have been working on cars a long time, but I'm always learning and open to advice.

The alternator showed an output of 14.5 volts on the bench tester at Autozone. I would hope they would test for bad diodes, but I'm not sure. The alternator didn't smell burnt, and I couldn't find anything that looked or smelled burnt when R & R the Alternator. I actually went to 2 stores and had it tested. The second store was O'riellys and the guy tested it 3 times in a row to try and get it hot. It passed every time.

I should have posted here before I reassembled the car. I would have replaced the alternator based on the advice I'm receiving here. . My Dad was an excellent mechanic and he was always encouraging me to diagnose the problem, and not just replace parts. I wasn't sure of best procedure. If I can't find another problem, I will try replacing alternator with Reman.


Thanks again to everyone for the help!

Re: Battery Light On Dash.. Alternator & Battery Test Good

I wanted to follow up.

I replaced the alternator with Reman from Autozone and the battery light is off.
My conclusion is the Alternator Test Equipment at Big Box Stores must not meet Range Rover Specs.


I removed Alternator and had it tested at 3 different stores (2 Autozone & 1 O'Riellys). It passed test at ll three locations.
I charged battery, and re-installed.
Battery light was on. I went back to Autozone and they tested Battery & Alternator on the car. It passed both tests.

I posted on this forum and people recommended that I replace alternator because 13.7v was not enough output.

I replaced alternator and it fixed the problem. New alternator seems to consistently charge above 14v.

Thanks for all the help!

Re: Battery Light On Dash.. Alternator & Battery Test Good

RABarrett said:

Referencing range Rover TSB's there is a possibility that the battery monitoring harness, which is fused, may have a blown fuse. This could result from a spike from the dying alternator. It may also be the result of a spike in the electrical system, say, from a jump. If you research this code on the internet, there are very specific instructions on repairing this code. Ray

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Thanks for the reply...
I read that TSB.
However, the fuse for the BMS harness is actually built into the harness itself. And I've already replaced the harness.
Here is a pic of the old fuse link harness wire (not blown)

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