Battery Connected Wrong Polarity
mistergrumpy - 16/1/12 at 05:04 PM
Bit of an embarassing moment earlier. I went to look at a van and as it had sat for a while he went to jump start it. He connected his leads, which
had a block on them with a green light on that I had never seen before, but he connected the other end to another battery and nothing was happening so
I looked at the van battery and noticed a few wires coming from the terminal with a huge + over the top which he had connected to the other batteries
negative. Anyway I says I think the leads are connected wrong and di he want me to switch them as he was sat in the van and he said yes.
Queue a big spark and the red light coming on the dash. He got out and looked and the + sign was actually a plug for topping the battery up 
Anyhow the dealer just replaced the van battery with another one and it started fine and ran but the red light stayed on. I agreed a price including a
short warranty and he said he would sort the red light even if it meant replacing the alternator. Great. But I'm wondering if there could be
other damage caused? As I said the van ran fine and everything just had the red battery light on.
Any idea's? Comments on what I tool I am?
daviep - 16/1/12 at 05:13 PM
Probably need to tell us what van it is? Is there a symbol with the red light?
We all do stupid things, they only ever happen when:
a) it doesn't belong to you or
b) when someone is watching or
c) both a & b
Regards
Davie
mistergrumpy - 16/1/12 at 05:39 PM
VW Transporter T4. It's the red battery light.
splitrivet - 16/1/12 at 05:43 PM
Probably taken the diode out in the alternator, but if it runs ok the rest should be OK. Was the radio working if not probably taken the protection
diode in that as well.
Cheers,
Bob
needforspeed - 16/1/12 at 05:52 PM
check main fuse 60 or 80 amp
mistergrumpy - 16/1/12 at 05:55 PM
As said the dealer said he'd replace the alternator if needed before handing it over which is reassuring but I was a bit worried about maybe the
ECU. Could there be damage here if the van was still running?
jollygreengiant - 16/1/12 at 06:51 PM
quote:
Originally posted by mistergrumpy
As said the dealer said he'd replace the alternator if needed before handing it over which is reassuring but I was a bit worried about maybe the
ECU. Could there be damage here if the van was still running?
At best the engine would run with an engine management light on, at worst the engine would not run, IF, there was any damage to the ECU.
splitrivet - 16/1/12 at 07:13 PM
Most ecu's have a bridge rectifier built in so that even with a misconnection they are still fed correctly.
Cheers,
Bob
perksy - 16/1/12 at 07:21 PM
Seen this happen a couple of times and each time all its done is take the Alternator out
So fingers crossed thats all it done
mistergrumpy - 16/1/12 at 07:22 PM
Great. Seems like all is not lost then. Phew!
Peteff - 16/1/12 at 07:39 PM
Isn't there a fuse in there to protect against incorrect polarity? When I did it on a bike it just blew the main fuse, one 30 amp fuse later and
up and running again.
austin man - 16/1/12 at 07:39 PM
get the alternator changed make sure hes not just removed the dash bulb so I would also take a test meter to see tht the new alternator is giving 14
volts on charging. PS welcome to the Transporter ownership. The link below may help you out over time. got me a T5 and loving it
http://www.vwt4forum.co.uk/
mistergrumpy - 16/1/12 at 08:03 PM
Cheers. Already a member on VWT4. I'll be looking for lots of help from there too, soon. 
austin man - 16/1/12 at 08:27 PM
will no doubt catch some of your posts on there then