defender 300Tdi ignition light coming on slightly

I've started running my 110, upgraded to a 300 Tdi. I need some advice please. The engine is unknown so expecting some teething problems. The first thing is the ignition warning light. It's flickering on idle and gets less when rev'ed up but still a little glow which is noticeable in the dark. What does it mean and where do I need to start to sort it out? Cheers, Paul

Check the voltage at the battery when its running.
Generally if the light is flickering you have a poor connection, or the alternator brushes are worn.

Check the voltage on the battery.
With the engine off.
With the engine ticking over.
With the engine revving.

When the engine revs it should be around 14.4V
12V or a little more on tickover.

If not it's the alternator.
There is a small wire connected to the back of the alternator, check the connection is good.
Check the earths on the bulkhead in the engine compartment. The earth point is approx behind the fan speed levers.

I've ordered a multimeter so will check and let you know. It has a usb charger with a voltage gauge on it and on tickover it's 12.4v
I'll check the little wire on the back of the alt tomorrow. I had a look at new alternator's. There are 65 amp, 100 amp and 120 amp. Does it matter which type? Other than a price difference. Many thanks for your help, appreciate it.

Gunter Butfuster said:

I've ordered a multimeter so will check and let you know. It has a usb charger with a voltage gauge on it and on tickover it's 12.4v
I'll check the little wire on the back of the alt tomorrow. I had a look at new alternator's. There are 65 amp, 100 amp and 120 amp. Does it matter which type? Other than a price difference. Many thanks for your help, appreciate it.

Click to expand...

So long as the alt has the same connections as yours it will be a straight swap, they all fit but some require wiring/terminal mods.
Defender traditionally had a low output alt, Iirc the 200 was only 45 amp, 65 should be more than enough.

Agree, 65amp is plenty for standard truck.

Need to measure voltage between the main terminal on the alt and the alt body too rule out bad connections

Also check that the drive belt is not over-tightened.

Hi, heres an update.
I removed the ground wires from the bulkhead terminal and cleaned them up with a bit of emery paper (nice n shinny) replaced but made no difference.
Then with new multi-meter in hand,
I checked the battery at idle = 12.4v then revving up no change (sometimes 12.5v)
Checking the alternator = thick brown wire terminal and ground to the body of the alt. 15.6v at idle.
I guess it looks like the alternator?
I want to have fitted a dual charging system (for camping etc.) would I then need an upgraded alt?
Cheers, Paul

15.6 sounds a bit high, but you need to figure out why you're getting only 12.5 at the battery

Agree 15.6 is a bit high but that is at the alternator not counting any losses in the wires. You should be getting 14.3-4 at the battery.
If you are getting a high reading 16v plus at the alternator when revving then I suspect its regulator fubar.

tottot said:

Agree 15.6 is a bit high but that is at the alternator not counting any losses in the wires. You should be getting 14.3-4 at the battery.
If you are getting a high reading 16v plus at the alternator when revving then I suspect its regulator fubar.

Click to expand...

Need to fix the wiring first though, might find the village drops back to normal when there's a load on it

Another update.
I thought I would take a photo of the back of the Alt to see the pattern of the terminals if I was to buy a new one,make sure it was the right one.
I was looking at the photo and suddenly noticed that the retaining nut for the thick brown cable was missing.
But now it's 15,5v at the battery on idle not diff revving up. Are the gubbins inside broke? Red flickering lights gone
Is this going to fry the battery?

I would only expect to see 15+ on the most modern cars with stop/start etc

It might simply be the alternator is trying to make up for the low state of battery charge, so maybe run it for an hour and see what the volts are reading, bit of luck the battery will come back to life.

Both my cars with A127 alts run at high 13 to low 14 volts, my D3 runs high 14 to low 15 volts all the time, tonight after standing for 4 days, on the 20 mile run home it showed 15.2 volts the whole journey.

lynall said:

It might simply be the alternator is trying to make up for the low state of battery charge, so maybe run it for an hour and see what the volts are reading, bit of luck the battery will come back to life.

Both my cars with A127 alts run at high 13 to low 14 volts, my D3 runs high 14 to low 15 volts all the time, tonight after standing for 4 days, on the 20 mile run home it showed 15.2 volts the whole journey.

Click to expand...

Ok thanks. I'll see how it goes for a few days

Fully charge the battery so you're on a good starting point

kermit_rr said:

Fully charge the battery so you're on a good starting point

Click to expand...

OK, wilco.

Update
Fully charged the battery, and battery shows 12.5v.
A slight change, the output is now from 14.8 or 9v to 15.1 or 2v
I have a spare 300tdi engine at my sisters. I'll visit a round the end of the month and swap the Alternators. The the spare shows a normal output I have the original one repaired.