Help please! Electrical issue with 1995 Defender 110 County, 300 tdi

Hello Landy Zone!

I'm a new Defender owner and a first time poster on this forum. I apologize if this is the incorrect format or post location. I'm grateful for any insight/guidance you an provide!

I am looking for help diagnosing and correcting an electrical problem with my 1995 Defender 110 County, 300 tdi.


Problem: When switching the ignition to position III, the battery voltage drops from ~12V to ~8V and then lacks the voltage required to turn the engine over. If connected to a jumper battery or another vehicle, I can turn the engine over. When connected to another running vehicle in parallel, the voltage climbs to ~13V; as soon as the other vehicle is disconnected, the voltage drops to ~11.9V.
Once turned over and with assistance disconnected, the voltage is steady at ~12V at idle; with the engine reved, the V climbs to ~13.
When left for several days without running, the battery discharges.

Additional info
- The battery is new.
- The Defender is mostly stock and low-mileage. It sat in a previous owner's grain silo in UK and is very well-preserved.
- The only modifications of which I am aware is a pair of Land Rover brand driving lights that were mounted to the front bumper. I have since disconnected the power source to these and insulated the power leads that were running to them. I have not traced these wires back into the dash and disconnected them though (the wire bundle for this appears in good shape and I'm not concerned about a short along this circuit).

Diagnostics thus far:
- Fuses: with the engine off and key out of ignition, I've connected a multimeter in series with the positive terminal of the battery and pulled each fuse under the dash and the 4 fuses in the engine bay one-at-a-time while taking note of the voltage drop. The most significant drop was under-dash fuse #2 which dropped from 11.76 V to 11.49 V. I've attached a photo of the fuse box as well as the fuse box key.
The only other voltage drop was from pulling the 60A fuse in the engine bay (3rd from the front, depicted with red arrow in picture attached) wherein the voltage dropped from 11.69 V to 11.32 V.

- Alternator: I've also disconnected the alternator and observed the voltage with all batter terminals connected (multi-meter in parallel). There was no voltage fluctuating with the alternator disconnected -- both when the engine is off/key out of ignition, as well as with the engine running. Since I've seen a number of posts discussing incorrect wiring of the alternator, I am including a picture of my current alternator wiring (attached).


Thank you for reading. Again, I am so grateful for any help!

Best,
Josh

Welcome to Landyzone and good news you are in the right section.
Couple of questions. How long have you had this issue and was it ok before?
Does the dash battery/ignition light go out when running?
Any other issues like poor lighting and or flickering of.

Welcome .

Ok first I would say your battery is not fully charged.
You have potentially bad /missing earth connections.
Your alternator out put is low so not charging the battery.
Your starter maybe on its way out.

Charge the battery .
Check and clean all earth straps Battery to body/chassis, engine to chassis. Look at the earth strap carefully they can break down inside insulation.

So start with the cheap/free fixes.

Sorry I really dont understand the checking for Voltage drop.

Good luck, let us know how you get on.

J

Try your volt meter on the large terminal of alternator engine running, should be reading 14. something v.

marjon said:

Welcome .

Ok first I would say your battery is not fully charged.
You have potentially bad /missing earth connections.
Your alternator out put is low so not charging the battery.
Your starter maybe on its way out.

Charge the battery .
Check and clean all earth straps Battery to body/chassis, engine to chassis. Look at the earth strap carefully they can break down inside insulation.

So start with the cheap/free fixes.

Sorry I really dont understand the checking for Voltage drop.

Good luck, let us know how you get on.

J

Click to expand...

You have said everything I was just typing out to say!

Agree the battery needs a good charge and go through the battery to chassis cables and other earthe cables between engine and chassis. Give all of them and the attachment area to clean and wire brushing so all the connections have a good low resistance connection.

I also do not follow the fuse pulling methodology. Pulling fuses should not create a voltage drop. I would be testing the other way around. Pull all the fuses and turn the ignition on there should be no drop. then put the fuses in one at a time and see which fuse then creates a drop when the ignition is turned on.

I would also be expecting a drop when the ignition is turned on as the 300tdi had the glow plugs on a timer relay which comes on when the ignition it turned on, rather than on a separate position of the key on older models. As soon as ignition is on the glow plugs will draw power, you could try removing this relay and see if the voltage drop changes, it is the relay in the centre of the bulkhead under the bonnet. (i believe seen just above the engine fuse box in your pic0

tottot said:

Try your volt meter on the large terminal of alternator engine running, should be reading 14. something v.

Click to expand...

If its earthed at the engine maybe not.
If its earthed at the Battery maybe.

Earths first free check.

J

Should have said earth to battery, engine earth may be rubbish. Mine came off recently [ broke when I jacked engine to renew mount rubber's ] and I did not notice Made all sorts of funny things happen, temp gauge lost the plot, LED voltage reader went like something at a fairground and headlamps sending morse code.