Battery light stays on

Robin-i'-the-Hood

Hello. Hope someone has an idea why the battery light might remain on on my Land Rover 110 with 200tdi engine. I replaced the alternator a year or so ago as I was concerned that the battery light would stay on after start up (but went out after going into gear and moving off) The other day it stayed on on a round trip of 6 miles (I thought it would go off any second). I don't want to risk driving it in case I run out of electricity, but it fires up happily enough. Any simple fixes before the auto electrician is called upon??

forgotmyname

Test the battery and alternator voltages.

Cheap test meter is all you need under £10.

Robin-i'-the-Hood

Got one of those...but not sure how to test the alternator or how to interpret what I find! ...testing battery terminals engine not started was 12 point something

Quiet_Spark

Start engine, switch headlights on, rev to 2000rpm, voltage across battery terminals needs to be a minimum of 13.8v and a maximum of 14.4v.

Possible causes of voltage readings outside of those figures can include loose battery cables, poor engine earth connection, defective regulator, defective brushes, etc.

bryanb

Robin-i'-the-Hood wrote: »

Got one of those...but not sure how to test the alternator or how to interpret what I find! ...testing battery terminals engine not started was 12 point something

It's the point something that's important.
12v is almost flat, 12.7v is almost fully charged, both figures when cold and engine has not run for an hour or two.

epninety

Well the bad news is there was probably nothing wrong with the old alternator. It's very common to see the light stay on on a tdi until you get the revs above idle. I have it on two of my LRs, no problems over the last 8 years or so.

200tdi doesn't need much battery power to run once started, so possibly it isn't charging now. I've driven around for a few days with no working alternator.

So, a few questions to answer before it can be diagnosed :-

Is the light permanently on, or only when the ignition is on?

Measure the voltage, directly across the battery terminals...
(1) when the engine has been stopped for a few minutes
(2) with the engine still stopped, but the headlights on
(3) With the engine started at idle
(4) with the engine running at 2000rpm. You probably don't have a rev counter, so just give it some revs

Next question, why ask on here? There's plenty on good LR specialist forums where there will be plenty of people to ask. I recommend LR4x4.com, but there are many others.

Stooby2

First thing to do would be to check the connections on the back of the alternator. Not uncommon for the 200Tdi (and the 300tdi) to shake the connections off.

Norman_Castle

Very obvious, but you haven't mentioned checking for a loose or missing belt.

Stooby2

That's because the belt does the PAS and water pump as well on a 200tdi so he'd know if it had failed. Loose belt would give itself away with the usual screeching noise you get.

new_home_owner_3

Quiet_Spark wrote: »

Start engine, switch headlights on, rev to 2000rpm, voltage across battery terminals needs to be a minimum of 13.8v and a maximum of 14.4v.

Possible causes of voltage readings outside of those figures can include loose battery cables, poor engine earth connection, defective regulator, defective brushes, etc.

This is the way to test if the alternator is working correctly, i suspect if the reading is not correct and you replaced the alternator, it will be lose connectors, battery or a loose belt.

You can also do it with a clamp meter, it is very similar to above but you will see discharge and charge readings, basically use the clamp meter and turn all your lights on and blowers and you will see the reading on the meter showing the battery discharging. then do the same with the engine started revving it between 2000 and 2500 rpm and and the reading on the clamp meter will move up and show it charging. This will mean you alternator is fine.

It could be you battery is no good have you checked fluid levels?
You might need to check the density of the electrolyte, this can be done with a hydrometer, the reading should be 1.280 from each cell and if it varies by 0.50 the battery needs replacing.