Power dropped off Igor!

Naigle

Member

Posts

14

Location

Cookham, Berkshire

• Dec 3, 2016

• #1

Hey, looking for some pointers to solve an issue with my 1995 90 (300tdi).

It's lost electrical power! headlights are dim, blower weak.... until, I put her in reverse and when the clutch bites... full electrical power is restored!!!

I put in a new battery last year and engine wise it's solid, starts perfectly, nice and lively.
During the day I don't notice anything is wrong.... at night when I'm using headlights and full blower in the current weather.

I'm guessing I have a bad earth/short on some cabling... Anyone have any pointers on where to start looking ? a casual scan doesn't show anything obvious wiring wise (visually).

If I can get this sorted, I'll finally get around to wiring in the heated seats!

Thanks in advance

Naigle

 

neilly

Well-Known Member

Posts

20,000

Location

Oxfordshireness

• Dec 3, 2016

• #2

Hi,

Might be worth using a jump lead to simulate an earth , may help you identify the area you need to look at if it is a dodgy earth.

Cheers

 

mikescuba

Well-Known Member

Posts

2,731

Location

France, Loire, Rhone Alpes

• Dec 3, 2016

• #3

+1 for a doggy earth.

 

bluedog333

Well-Known Member

Posts

5,436

Location

Henley on Thames, Oxfordshire

• Dec 3, 2016

• #4

Wiring to the reverse light switch can sometimes rub on the chassis and short out, causing electrical gremlins. Worth a look.

 

Disco1BFG

Well-Known Member

Full Member

Posts

6,316

Location

Buxton

• Dec 3, 2016

• #5

An extra earth, as mentioned above by Neilly, post #2 will almost certainly prove the issue.... and....

bluedog333 said:

Wiring to the reverse light switch can sometimes rub on the chassis and short out, causing electrical gremlins. Worth a look.

Click to expand...

This ^^^ plus, if an engine earth strap has failed, and the alternator is earthing through the reversing light switch/wiring, it could get a bit messy.... so have a look ASAP.

The alternative earth for an alternator is sometimes the handbrake cable... and this can end quite badly - specially if, the now "heat treated" cable fails!

 

Naigle

Member

Posts

14

Location

Cookham, Berkshire

• Dec 3, 2016

• #6

Thanks everyone... I take a look around the Alternator and reversing switch... I've not thought about using a temp second earth to help diagnose, so will give that a go as well...

I'll report back.

Naigle

 

Naigle

Member

Posts

14

Location

Cookham, Berkshire

• Dec 4, 2016

• #7

No Joy on the 30min I could spend today... what I need is a little helper to watch the headlights whilst I'm under the truck or head in the bonnet!
I'll get one of the kids to wrap up and help out...

I've checked that the battery is sound and main earth cable to engine/gearbox is good...
The reversing switch> cable is clean and no interference with the chassis.
The Alternator doesn't seem to be the issue (tried a jumper cable to good earth).. no change.
I'll take a look at the fuse/relay box next time.

I WILL find this issue....

Naigle

 

Naigle

Member

Posts

14

Location

Cookham, Berkshire

• Nov 7, 2021

• #8

Logging back into forum for a different reason and realising I never posted conclusion.....

Dodgy earth indeed.
I put a new braided earth strap between the chassis and the gearbox and 100% fixed.

I found by using a single jump cable connected to the negative of the battery directly and hunting around the various earthing components.
Thanks for the advice all.