Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 12 volt wiring help please!

Good evening all, have a problem that I’d like some help with please!

I want to hook the car up to a battery conditioner and am hoping to use one I already have that was designed to use with a BMW motorbike.

The unit output is marked “out 12V=1 A” then a space and “ta 40/E”

I’ve assumed that this unit (branded BMW) would do the job so went to plug it in via the cigarette socket only to find the plug on the end of the unit was much smaller than the cigarette lighter socket.

So I bought a bigger plug, which was attached to 6 foot of wiring and have soldered the wires on the new plug to the output wires on the conditioner.

This is where I need some guidance, please!

The wires on the unit are red/black and black.

The wires on the new plug are red/black and red.

I cut the old 12v plug off the conditioner and have connected the red/black to the red/black and the red to the black.

However when I plugged it into the car, the “ error” light lit on the conditioner.

The new plug has an LED on it to tell you if it’s getting power - and this is lit.

So before I swap the wires over, do people think :

1) the wires should be wired the other way round or

2) the conditioner is not up to the job or

3) it’s a different problem..

I appreciate in the ideal world I would not charge via the cig lighter but direct wire a fused plug to the battery. I will sort that at some point when I’ve got time but want to, for now, take the easy option!

Thoughts please!

Regardless of colour, the wire that goes to the centre contact of the plug is going to be positive. so the wire that went to the centre connector of the old plug should go to the centre connector of the new plug.

Plus, you may need to check that the accessory socket is live with ignition off. If it isn't you will have to wire in a socket to the battery (via a fuse).

Never rely on colourcode! Always use a voltmeter to check which wire is positive (+) and which is negative (-). The pin on the plug should be positive (+).

If that is correct and there is still an error, it could be the conditioner is not up to the job (with a pourly charged battery) as it is only 1A.

Thanks for the replies everyone.

I think this (quote) is the nub of the matter. Looking at the CTEK chargers that seem to be favoured here, they seem to be 3.8 or 5 volt so is suspect that my conditioner is not up to the job.

Also reading about the charger I’ve got, it was for a BMW GSA which has Canbus electrics - I wonder whether this means the charger isn’t compatible with a non-Canbus vehicle? (Not my strong point, so may have nothing to do with it!)

on some of these plugs there is a fuse in the centre pin if it is rated at 1amp and you have a flat battery it will try and draw a higher current.. (it's to do with the internal resistance of the battery)

David Byrne

FW

You've just spent a not insignificant sum on a new car.

Get a new conditioner (C-Tek is a good start) and if the socket is not permanently live, get a qualified automotive electrician to wire in a new fused socket close to where the battery is located.

By your own admission, you're not an expert. So, in my opinion, don't experiment on your new car.

I personally wouldn’t can the idea without changing the wires over and try that

I’m pretty sure all automotive 12v batteries will charge in a similar way

I don’t think it will harm anything - if it’s not right it will just stop with another error message

I wired my charger for my last Mog up wrong as I put a lighter socket charger on and it just beeped at me with Error first

A quick update, thanks again to everyone whose responded.

I have checked that the cigarette socket is live when the ignition is off: I can confirm the socket is live, I have a 12 volt light that plugs into cig socket and that worked.

Fuse in the plug is intact, I couldn’t read what it was rated at though but the details on Amazon say it is fitted with a 10amp fuse - so presume that it is.

I think the wiring is the right way round, as the charger shows all being well for a few seconds then the error light comes on. I would think a wiring issue would be binary- it would work or it wouldn’t.

Ivor Mog - you make a very good point, I can’t argue your logic!

So tomorrow CTEK 5.0 will be procured...

Thanks again for all the pointers.

Get it hard wired, not difficult. There have been cases where cars have caught fire using the power socket.