Electrical issue Merc OH1418

[Kappy]

Hi Guys,

Looking for some guidance regarding an electrical/starter issue.

Recently notice I had no dash lights and the handbrake tell tail light not working,

So dismantled the dah housing and discovered a plug linked to brake tell tale lighth was disconnected.

Checking dash tight I discovered a couple of instrument lights blown, so replaced lights.

Still no dash lights, then turn on key and no dash lights at all, but turn key and engine starts, but no instruments working ie, oil pressure, voltage fuel gauge etc .

Check fuses and discover fuse blown.

Replace fuse, return to cab turn key and hear noise from where fuse is same as before engine starts no instraments.

Recheck fuse and blown.

So check nothing has changed or been really altered from when all was working except for instrument lights.

Electrics not really my forte, interested in some simple guidance/logic if possible.

Info on OH1418 appreciated, please don't suggest google deed end.

Cheers
Kappy

[dapope]

Not a spaarky, but I would start by checking the wiring on the blown circuits...looking for damage or burning..

[Busman]

Betcha it is a bad ground (negative or return to the battery) First and most obvious place to look, and easily disturbed without realising it.

[BruceS]

First suggestion is to grab a manually re-setable fuse to hook across where it's blowing that fuse or you'll empty your spare fuse container REAL quick.
Then you need to make sure you have a good printout of fuse positions & the Amps rating of each one.
If it's like my old Benz a lot of positions are empty anyway?
Once you've removed most, try if it still shorts out or not. If it doesn't, start replacing one by one till you find that one that does it.
All wires black?

[Kappy]

Strange that it just started without any real cahnge.

Thanks busman, I'll double check the battery as the only option I had just reconnected the negative to the battery after having them on charge.

Hopefully its that simple.

[Busman]

Realistically one simple piece of equipment will have you learning about DC electrics pretty quick.
Any decent Digital Multi Meter (DMM) will have a continuity section, usually you just put on Ohms setting (like a horseshoe) and if you put the red and black probes together you will get a noise, a buzz, or at the minimum a light. This shows continuity or a circuit is present.
Without power on you could put one side (doesn't matter which) onto the globes you replaced (positive or live side) and the other onto the fuse block. This will tell you if there is a circuit between the fuse and the globe (light switch on).
If you can borrow a DMM it is very easy to learn how to trace a wire.
Everyone I know with a big rig carries one, as well as 15 metres of wire, to reach every part of the rig. Makes fault finding evry easy.

[Kappy]

Just an update on my progress.

I disconnected the negative link on the battery/s and re connected.

Turn on ignition and I have dash instruments again brake light/glow plug etc, but still dash illumination lights.

Also now I notice Air Brake Parking Light is now not on even though air was down to 2.

As I have the dash in pieces and the park brake lever sitting to one side I noticed a line that is attached to the bottom of the park brake mechanism has come adrift, looks like fitting is dodgy, but air still builds with it disconnected.

I was gonna post a pic but couldn't get it small enough even though its 27KB.