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.

Thanks all!!

I took a less responsible and more expensive approach… (spoiler, it didn’t work).

Problem review: when key ignition is turned from position 1 to position 2, voltage at battery drops from ~11.5V to ~5V before climbing back to ~9V.

Bottom line up front… it is NOT:
-the ground to the starter motor (checked by bypassing directly to the negative terminal of battery)
-the starter motor itself (replaced)
-the ignition switch (replaced)

I guess the best first step was to find all the grounds/earths (as so many suggested). Can someone provide guidance on where all the key earths are located? (Photos appreciated!).

Any other things to test?

Also, does anyone know the torque specifications for the starter motor bolts? Still need to final tighten.

If you check out Defender 300 "behind dash earth" on you tube a fair bit of info comes up about it and other earth positions.
Torque settings on starter bolts not critical but can be found in manual, book or on line. I just tighten with a normal socket wrench.
The voltage drop and rise again is likely the glow plug relay doing its job.
It may be worth checking the condition of the main power supply cable from batt to starter.
I had one that had black wire corrosion in the first few inch's from the batt resulting in slow starter. New cable and terminal had it sorted.

The 300tdi employs a heater plug timer relay. This is on the bulkhead, inside the engine bay.
In position 2 this relay is energised and the heater plugs take a lot of current which does 'drop' the battery voltage.

Typically this drop is to around 11.x volts.
Then after a while it recovers (as the timer clicks off - which you can often hear if you wait long enough).
The fact that your battery goes below the expected 11V does indicate that it is not fully charged/faulty.
The fact that the voltage drops to below 9V screams that it's not charged/faulty.

There is a 'key' earth on the transfer/gearbox to the chassis.
Starter bolts are M10, I tighten mine to around 50NM.



My main earth (inc the winch cable)

The fact that we are never seeing anything like a good charged battery voltage is, well .

The glowplug being taken out of the initial switching on would be a good place to start as ^^^.

We also don't see anymore info on the low alternator charge reading.

J

Anything less than 12.3v is a flat battery.

This flat battery has been pointed out, but sadly completely ignored by @Joshk5000.

The battery maybe new to you, but I would suggest it's fooked.

Thanks everyone! Here is an update:

I’ve checked the main earth to the transfer/gearbox. The bolt was clean but I checked the main earth cable itself by bypassing it with a jumper cable directly to the battery. Then tests: ignition to position 2 still results in a drop from 11.xV to 6.xV… after the timing relay, there’s a return to around 7.xV. So it doesn’t seem like that particular earth is the problem. Are there others I should check?

As well, I totally disconnected the batter and charged it with another vehicle. It held stable at 13V after charging then when removed form external power fell to 12.xV and drifted into 11.xV with enough time. Connecting back to the defender (and without external power), it held in the low 11’s… this was a new battery as of a few months ago, is this the primary problem?

Still, hard to understand that there isn’t a short somewhere…? If I just replace the battery (again), won’t this problem recur?

Grateful for your help!

Joshk5000 said:

<snip>
As well, I totally disconnected the batter and charged it with another vehicle. It held stable at 13V after charging then when removed form external power fell to 12.xV and drifted into 11.xV with enough time. Connecting back to the defender (and without external power), it held in the low 11’s… this was a new battery as of a few months ago, is this the primary problem?

Click to expand...

It does sound like you have a faulty battery.
Can you fit your battery to this other vehicle and fit their battery to your defender ?

Your battery (when charged) should sit around 12.6 to 12.7V
A battery can 'appear' to be OK when checked for voltage but can be seen to be defective when a high current is drawn from it.

I recently had a similar issue with my wee 125 scooter. The voltage seemed fine but would only start the bike once or twice yet the voltage still seemed to be OK.
New battery and it's as right as rain.

I have a battery tester if you are near Lanark

Joshk5000 said:

Thanks everyone! Here is an update:

I’ve checked the main earth to the transfer/gearbox. The bolt was clean but I checked the main earth cable itself by bypassing it with a jumper cable directly to the battery. Then tests: ignition to position 2 still results in a drop from 11.xV to 6.xV… after the timing relay, there’s a return to around 7.xV. So it doesn’t seem like that particular earth is the problem. Are there others I should check?

As well, I totally disconnected the batter and charged it with another vehicle. It held stable at 13V after charging then when removed form external power fell to 12.xV and drifted into 11.xV with enough time. Connecting back to the defender (and without external power), it held in the low 11’s… this was a new battery as of a few months ago, is this the primary problem?

Still, hard to understand that there isn’t a short somewhere…? If I just replace the battery (again), won’t this problem recur?

Grateful for your help!

Click to expand...

Your battery is fooked.
Fooked your is battery.
Battery is your fooked.
Is your battery fooked.
Your fooked battery is.

I bought a new Bosch battery once, put it on the car and worked lovely.
A week later nothing, dead as a Dodo, got another one under warranty which was fine.

Alright! I’ve ordered a new Varta 110 to nuke the problem with the battery as empiric source. Hoping that does it! Will update in a few days when I’ve got it.

In the meantime, there must be other earths to check, right? The main earth from the battery goes to the gearbox and there are no other connections to it. Where else can I check/clean while waiting for this battery?

As always, thanks LandyZone brain trust! You guys are great!

I would buy an earth lead (just a generic one from halfords/local motor factor) and put it from the battery to chassis, as a lot of the electrics earth through the bulkhead/chassis.

GRATCH said:

I would buy an earth lead (just a generic one from halfords/local motor factor) and put it from the battery to chassis, as a lot of the electrics earth through the bulkhead/chassis.

Click to expand...

This is helpful. Any recommendations on where on the chassis? I suppose I could route a cable out of the battery compartment along with the earth to the gearbox?

The earth goes from battery to gearbox/transfer box, it branches of to the chassis rail near the gearbox.
If you have no earth to chassis then that could be your problem.
You need a heavy earth cable from engine or gearbox going to the chassis. Doesn't really matter too much where but the more the merrier.