Electrics this time!!

Landyfox · May 3, 2018

Just like last year, the day before the MOT an issue suddenly arises out of the blue that I can’t figure out... this time it’s an electrical fault. The rear Left Indicator/repeater to be more precise.

Everything has been functioning as it should, then yesterday the rear indicator suddenly overnight stopped working. Foolishly, I assumed it was a blown bulb or maybe a lose wire as the front and side repeaters were working fine, although much faster. When I’ve taken the bulb out, everything appears ok visually. The bulb is not blown and there appears to be power on positive wire and a nice clean and secure ground without any paint or debris impeding the connection. I’m out of ideas and obviously anxious about MOT tomorrow.

What I’ve done so far (everything in the list at least 3 times just to make sure)...
- Replaced the bulb with a known working one.
- Replaced the bulb holder with a known working one.
- Cleaned the connections back to bright copper wire before attaching new terminals.
- I’ve tested old bulb and holder in a working lamp.
- Created a new earth test wire directly to the negative on the battery.

What I find baffling, when using a multimeter there is power to the indicator, the reading alternates with the flash pattern... voltage readings similar to this.... 2.1, 6.0, 7.4, 0.8, 3.2, 5 and so on! With it being an early Defender 300TDi 90, I have additional wires behind the rear Right brake light for a towbar harness to be attached, the older black female bullet terminals. Just to eliminate variables, I thought I would connect bulb up the corresponding wire (GR) in the towbar harnes..... the exact same issue. Volitage ranging between 0.8 to 7vlts on multimeter, but no illumination on the bulb or test lamp....

I’m past head scratching now, I’m firmly banging my head against the wall. Has anyone experienced similar issues or maybe understands what’s going on. As always thanks

Landyfox · May 3, 2018

I forgot to mention.... the rear Left break light doesn’t seem to work either. The lamp works as it should, just not the break. I assume that’s a bulb, but thought I would mention it just in case it was relevant.

Flossie · May 3, 2018

The wiring for the rear left comes from behind the rear right lamp cover. Have a look there.

Landyfox · May 3, 2018

Flossie said:
The wiring for the rear left comes from behind the rear right lamp cover. Have a look there.

That’s where the tow bar harness is located, I’ve tried testing most the wires behind there. I’m confused as why I can still be recording voltage yet no illumination.?!

Landyfox · May 3, 2018

I’ve even unplugged the connector in the engine bay and checked that there is continuity to the rear wires!

As I say, it’s been working tremendously well of late, than this morning this...‍

‍

jamesmartin · May 3, 2018

Landyfox said:
I’ve even unplugged the connector in the engine bay and checked that there is continuity to the rear wires!

As I say, it’s been working tremendously well of late, than this morning this...‍‍‍

it is it the 300 style black small pin connector

Landyfox · May 3, 2018

jamesmartin said:
it is it the 300 style black small pin connector

Hi James.... no it’s a two prong plug. Earth wire and a Green with Red stripe. I thought that was at fault so fitted a new one but exact same issue.

Jimsky Korsokov · May 3, 2018

I think the clue to this is that the remaining indicators are flashing too fast - a sure sign that something is wrong somewhere as this is determined by the circuit resistance (see https://www.2carpros.com/articles/turn-signals-blink-rapidly)

May be related - on a friend Landy we had power to the headlight full beam, but when trying it no light came on. Clue there was that the voltage dropped on application to 9V instead of 12V. This was caused by a corroded connection at the fuse box essentially nicking most of the power leaving too little to produce light. Once we found the corroded contact and remade it - a glorious 12V illuminattion occurred.

Lesson is that poor contacts can cause great confusion - your low volt measurements could be for the same reason.

Landyfox · May 3, 2018

Jimsky Korsokov said:
I think the clue to this is that the remaining indicators are flashing too fast - a sure sign that something is wrong somewhere as this is determined by the circuit resistance (see https://www.2carpros.com/articles/turn-signals-blink-rapidly)

May be related - on a friend Landy we had power to the headlight full beam, but when trying it no light came on. Clue there was that the voltage dropped on application to 9V instead of 12V. This was caused by a corroded connection at the fuse box essentially nicking most of the power leaving too little to produce light. Once we found the corroded contact and remade it - a glorious 12V illuminattion occurred.

Lesson is that poor contacts can cause great confusion - your low volt measurements could be for the same reason.

I suspect they running fast because it’s not recognising the bulb, thus creating a brake in the circuit. But that’s problem, there’s power and good ground connections, bulb just won’t illuminate.

Landyfox · May 3, 2018

Jimsky Korsokov said:
I think the clue to this is that the remaining indicators are flashing too fast - a sure sign that something is wrong somewhere as this is determined by the circuit resistance (see https://www.2carpros.com/articles/turn-signals-blink-rapidly)

May be related - on a friend Landy we had power to the headlight full beam, but when trying it no light came on. Clue there was that the voltage dropped on application to 9V instead of 12V. This was caused by a corroded connection at the fuse box essentially nicking most of the power leaving too little to produce light. Once we found the corroded contact and remade it - a glorious 12V illuminattion occurred.

Lesson is that poor contacts can cause great confusion - your low volt measurements could be for the same reason.

Sorry I forgot to mention, the remaining indicators have the same volt drop.

Jimsky Korsokov · May 3, 2018

Does it light when you put the hazard's on?

Landyfox · May 3, 2018

Jimsky Korsokov said:
Does it light when you put the hazard's on?

No, but they don’t speed up, they flash at normal pace.

jamesmartin · May 3, 2018

faster flashing is a symptom of a bulb not working not a cause ,usually its a connection,earth or the holder

Landyfox · May 3, 2018

jamesmartin said:
faster flashing is a symptom of a bulb not working not a cause ,usually its a connection,earth or the holder

That’s what I thought. But I’ve cleaned and checked earths. Even used a test cable directly to a battery negative. I’ve replaced bulb and holder with a known working one. Also tested bulb and bulb holder in a deferent lamp, both work. I’ve replaced the connector. I’m just stumped

jamesmartin · May 3, 2018

must be a poor feed to the lamp then

Jimsky Korsokov · May 3, 2018

If the brake light is also not working, has some part of the loom got crushed somewhere? Afraid I'm out of ideas .... normally solve these by spending huge hours with a multimeter .. finally working out what it was having come up with many dumb hypothesis along the way.

My money would still be on a bad connection on the +ve wire dragging the voltage down. The symptoms are a decent static voltage, but pulled down drastically under load.

Good luck tomorrow with the MOT - hope you get it worked out - will probably come to you at 3am!

Landyfox · May 3, 2018

I’m going to try and run a new feed wire from the engine bay and see how that fairs

Landyfox · May 4, 2018

Does anyone know what the voltage should be reading when the indicator is switched on.?

zeaphod · May 4, 2018

I'd be looking for 10v at least. Run a temporary earth to the bulb holder and retry - if that doesn't work, run a 12v feed wire to the indicator connection point where the rear loom ends (back drivers side of tub) to prove the bulb and holder. If the earth is OK it's most likely the trailer wiring/socket, you could also try disconnecting that.

jamesmartin · May 4, 2018

Landyfox said:
Does anyone know what the voltage should be reading when the indicator is switched on.?

it will vary you wont get a 12v reading with a std multimeter

Electrics this time!!

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