2008 Mk 7 Minibus electrical fault.

[Bridget]

Hi, Hope someone can help.
I’ve owned my 2008 ex-minibus since March 2022. I bought it with just 10,000 miles on the clock. It now has 40,000. Since being in my care, I converted in a very basic way to a camper, serviced annually and looked after it. It hasn’t missed a beat until now. One month ago, I drove it home during my lunch break, came back 45 minutes later and turned the key, but nothing happened. No ignition at all. The immobiliser light continued to flash so I assume, stayed active. Doors locks didn’t work, or lights, but interior lights were on. I work at a bus company so the mechanic came to take a look. Tested fuses but could find out what had blown, but did find out that one of the batteries was only giving out 9v, so i put a new one in when we Towed it to work where an Auto-electrician changed a master fuse, under the driver seat (On the fuse cover near to the batteries, it says this fuse should be 60w, he’s put in a 100w fuse which concerns me). I asked what had caused the fuse to blow but he didn’t know. I drove it home, popped out the next day, no issues. Monday morning, turn the key, Nothing again. Just the immobiliser light flashing and no ignition. It seems that the fuse blows when I turn the ignition off. Does anyone have an idea of where would be a good place to start on finding out why the master fuse is blowing? It’s been off the road for a month.

[DanMK7uk]

I cant be of massive help. But ignition switches can cause a whole host of electrical gremlins.

Cheap and easy to try.

If its not tripping whilst driving, you would think overall, its mostly ok.

But that’s just my two cents.

[T350camper]

Has the master fuse blown a second time? That's a really big fuse to blow! You'd expect something major to cause that. I wouldn't replace a 60w fuse with a 100w fuse. The idea is that the fuse breaks the circuit if there's a short or overload. If the fuse is rated above the capacity of the wiring, then there's no safety net.

It sounds more like a drain on the batteries which is draining them when parked (the master fuse...unless it's gone again, could be a red herring). If one battery is strong and the other is weak, then the weak battery will drain the good one and leave both discharged.

I'd also go with Dan's suggestion and change the ignition switch (cheap and easy) just in case that has something to do with the drain.

[Bridget]

As mentioned, I did change the battery that was only showing 9v so have 2 good batteries. Voltmeter shows both fully charged so not a battery issue. I’ll see if i can change the ignition switch and go from there. Thanks.

[tranmx2]

The fault is usually after the fuse.
Changing the fuse does not fix the fault.
A fuse blows because of too much current flowing through it. Such as a direct path from the + battery terminal to the negative battery terminal - there being no resistance in the circuit.
Was the 60 A fuse the right one?
The box adjacent to the batteries is likely to be power distribution. The electric is routed to different parts of the van - usually goes through the starter switch from the battery to the unit that consumes the electric.

Elelectric systems do much the same thing but the circuits can be different. You need to know what is on the van - your 2008 is different than the 2012.
The bus electrician likely is not going to be familiar with the Transit set up. May have put in the 100 A fuse to get you home and maybe it was the only fuse available.
2008 to 2025 = 17 yrs old. It's been modified. Did a screw go into a harness? Has the vibration finally cut the insulation and shorted out the wiring?
Get the correct info'. Supposedly it was possible to get relevent wiring diagrams - shematics - from Ford. There is info' on the site re' getting it - whether or not that is still possible has not been acertained.

Might be. Look at the starter motor wiring and solenoid.
From the starter switch the solenoid is activated.
The solenoid closes a switch to cause electric to flow to the starter motor. There can be a short within the starter motor assembly. The brushes are likely candidates. Electric can - track - make a path through dirt. At first it's a trickly but overtime the path - track - becomes less resistant.
Likely it is cheaper to replace the starter unit rather than to repair it.