Main Fuse for vehicle battery?

Rayclash

New Member
If you for some reason connected the battery terminals incorrectly ( don’t ask how just yet !! ) What fuse is going to blow? Will it do any other damage 2018 T6 dual clutch
 
Probably won't blow any fuses because you haven't drawn excessive current.
The problem is you may of damaged any ECU which doesn't have reverse polarity protection. The only way is to connect them up the right way and see what's not working.

edit - you may blow a fuse if you have a 2nd battery
 
I think it drew a lot of current as it was connected for 15 seconds when the jump leads started to melt. It disconnected immediately but that was a lot of current they are heavy duty truck jump leads
 
All of the main power fuses and relays sit beneath the battery. That’s where I would start to look.
 
Is it completely dead ie none of the electrics work, not even stuff that should work without the key in ?

Pete
 
Have you tried disconnecting the main battery and reconnecting it after a few mins? May be worth a go.
 
How about lights - sides should come on without a key. Also interior lights.
Have you measured the battery voltage with it disconnected ?

Pete
 
Have you tried disconnecting the main battery and reconnecting it after a few mins? May be worth a go.
I’ll try today. But I suspect a lot of current went somewhere, the lights in the back are on the utility battery and they all work ok. So it would have to be the engine electrics that was affected. ( thanks for all the suggestions chaps)
 
How about lights - sides should come on without a key. Also interior lights.
Have you measured the battery voltage with it disconnected ?

Pete
Battery was brand new. No not checked lights yet. I gave up last night as I didn’t want to knacker anything else in the dark.
 
Definitely check the battery voltage. It may be the damaged component.

Pete
 
How do jump leads come into this by the way ?
Describing what happened could be useful.

Pete
 
Ok so you mean check the battery volts when connected : as if something is faulty it will draw down the battery ?
No, disconnect one or both battery leads, and measure the voltage across the terminals with a voltmeter.

Pete
 
Ok two vehicles with flat batteries, one Landrover has been flat for a while : needed to move T6 back 4m to under some lights as it was in the dark ( completely dark in a barn ) and I could not see to put in new battery. Used the jump leads on the defender to new battery and moved it out of the way. Wanted to do the same with the T6, I just needed to power up to put it in neutral to push it back, so though I’d do this with its new battery and long truck jump leads - no battery in vehicle ) was dark at the back of a barn : and I just got the leads the wrong was round, pretty stupid I know, it only took 20 seconds for the leads to start to smoke : I kicked the lead off the battery immediately. Didn’t get chance to take it out of park. It’s The DSG model 8 speed dual clutch. Superb bit of kit actually. When it’s not blown up.
 
Definitely need to check state of the battery with a voltmeter - it may be completely knackered.
For jump leads to melt, we are talking lots of current. There isn’t a fuse of that capacity in the T6 system to my knowledge, so it is more likely that something has melted in the electrics.
I would follow the wires through from the +ve terminal looking for damage.
To be honest though, you need an experienced vehicle electrician here.

Pete
 
Not good.

Could be a job for VW Assist or auto electrician to start metering things out.

Master fuse box under battery tray as per above.

Possible ECU, component and loom damage with a reversed battery scenario.

I've seen this before made the alternator go dead short which fried the alternator and took out the loom.

Possible fire risk.... you need to have this looked at by the right people.

VW assist could take a look, then if need be, get it lifted to the dealer.


.....

If it was me,

I'd remove the battery and test it.

I'd check the resistance or impedance of the battery leads to test for shorts.

I'd connect a low current charger, power supply (say 15A) and test the current drawn by the van.

Then scan for modules and start testing circuits.

I'd check every single fuse.

.......
 
If the leads were smoking, you've drawn a lot of current.

What stopped them smoking? If a fuse blew, it should of stopped smoking but if you pulled the leads off, you may be ok. I can only assume you have a battery to battery charger and hence putting the leads on the wrong way will cause them to smoke.

Disconnecting the second battery including your B2B charger, and then try again with the new battery (if it's ok still). It shouldn't cause the leads to start smoking again, but if it does, you'll have to isolate circuits to find out why. To do this, remove the bolt in fuses under the battery.
 
Back
Top