Fuse melting engine cuts out - help please

Can someone point me in the right direction please ?

Back in Feb I was driving along and my engine just cut out.
I changed/fiddled with fuse 9 and off I went.
@snotty pointed out that this shouldn't ever happen.
18 years ago an immobiliser was installed (no issues until now), so my electrics are not as VW intended.

I know I need to get rid/change the immobiliser so my engine can't cut out whilst driving- potentially dangerous.

Anyway it did it on the way to the peaks last week and again on the way home!
Fuse 9 melted rather than blew.

So I need to sort it, but have little idea about electrics.

Photos to follow

 

Possibly useful info:
Red and white wire enters from below the fuse box and seems to go to below fuse 8.
I assume this is the main 'power' feed entering the bus.

A big red wire goes from the top of the fuse box (9) towards the ignition.
On my fuse 9 is Immobiliser, G & Oil pressure lights, fuel gauge etc. Ignition circuit?

How do I narrow down what item(s) on fuse 9 could be causing the overheating issue?

Hopefully these photos will help

Since the photo I've changed the terminal on the end of the big red wire, so there is no exposed wire.

2nd photo is probably the same 'big red wire' disappearing near the ignition.

Fuse 11 also has the G & Oil lights, fuel gauge and indicators on it. When I pull this fuse my engine does not cut out! So immobiliser not on this circuit.

Immobiliser wires are tiny, so doubt they are the cause of the overheating fuse/too much load etc

 

All fuses
Melted fuse 9 holder

Have a look at the melted plastic above fuse 9 - once i've found what is causing the problem, will i need to change the fuse box as the connection on fuse 9 will be crap?

 

From below the fuse box

 

Ignition will be the biggest demand on those two connections, there joined at the base so as you see bid red and white feom the battery head a off down the red to the ignition..

Mine had been a bit hot but had been messed with to take headlight feed off same..



Ignition also comes off the unfused side next to it which would suggest that's where the problem might be as it can get hot without blowing a fuse.. but electrictrickery types will be along soon with sensible advice...

Sent from my SM-G930F using Tapatalk

 

That maroon was is oversized too..

Sent from my SM-G930F using Tapatalk

 

The supply to the ignition switch should be the same side of the fuse as the fuse supply i.e. unfused, at the bottom. You'll see this is also the the supply to always on stuff like your interior lights.
Fuse 8&9 will be linked at the bottom so red/white supply on one and red to ignition switch on the other. At the moment you're putting starter solenoid current and everything that runs via coil through a fuse and you shouldn't be.
The melted fuse holder will probably be fine when you stop over loading it.

 

For it to melt like that means that there is a large overload, probably a dead short somewhere. It could be inside the afore mentioned immobiliser or just a trapped or frayed wire touching bare metal.

 

^this makes sense. Where does that thick red wire go to?

 

Thanks @Deefer66 & @zedders

I'm struggling to understand the fused / unfused bit

I Appreciate that it all shouldn't be going through the fuse, but it has been for 18 years.

 

The really thick red wire goes from the top of fuse 9 and then towards the ignition

 

The fact that the holder melted rather than the fuse blowing concerns me. That fuse is too big and the current going through there is too large.

 

Is it actually connected to the ignition switch? Have a squint under the column. Zed’s theory sounds correct to me. The ignition/ignition switch supply should be unfused.

 

Yes I need to sort it.

Im assuming a problem has recently developed (eg a short) as it hasn't been an issue for 18 years

 

I'll go and check it out.

 

You need to do some circuit testing I'm afraid. For instance with all switched off and your battery earth disconnected you should not measure any resistance between the battery +ve and earth.
That's your start point. If you measure resistance remove fuses one at a time until it disappears.
From then on, attach multimeter lead to an earth point at the front, anything will do, detach wires from the fuse that you narrowed it down to and look for resistance between them and your earth point. Now you've narrowed it down to a single circuit. Follow it and keep doing the same basic test until you find the culpret.

 

I've been and looked under the column and i can't really tell where the big red wire goes as its all taped up.

I'll post a photo in case that helps.

 

I hate electricians tape over wiring. In the name of making something tidy all it does is makes future jobs more difficult and covers everything with a sticky mess to boot! Grr.
It does have its uses though, but I got a 100 pack of velcro tie wraps for a couple quid, I use them for most stuff that doesnt have to be heat, oil or petrol resistant.

 

I can`t offer anything apart from moral support and seeing if anyone can recommend a GOOD auto electrician in the area , doesn`t have to VW specific just good . I had a great guy in Leeds but he`s retired .

I think you`re about the same level as me when it comes to electrickery , i can be looking all day but not quite seeing what a pro will spot in a couple of minutes.
Sometimes it`s better to bite the bullet and let someone else have a look as you`ve said yourself , it`s dangerous .

Edit :- @Merlin Cat might know someone ??

 

Is there an actual immobiliser unit you can see and if so does it have anything to identify it by. I have a rather old Bosch 20i alarm system fitted to mine. With a bit of googling I've worked out where all the wires are going and why it was randomly setting off the alarm and cutting the starter. Fortunately it didn't cut the engine once it was going, only made it hard to start. The main reason it did this was because the radio earth was loose so it was protecting against it getting nicked.