27 replies to this topic

[hystrix cristata]

Model: Morris mini traveller
Year: 1969
Description of problem (please be as in depth as possible):

I bought a 1969 traveller that's been off the road for a few years. The previous owner recently changed the battery and has wired it up positive earth, is this correct? The car does start and runs but there are a couple of electric glitches. The horn doesn't work,one headlight is realy dim,the indicators flash realy slowly,the fuel gague doesn't move and the ignition warning light stays on.
So should it be positive earth, would it still start if it should actually be negative? Would any of the problems above be related to the battery being in the wrong way round?

I've got a haynes for 1959-1969 that only mentions positive earth and a haynes for 1969-1982 that only mentions negative earth. So I'm at a bit of a loss.

[Rosslin Racing]

if it has an alternator then i would say its positive earth also the lights may well be an earth problem, and the horn has not been used for so long that its knacked or just rusted

Edited by Rosslin Racing, 15 November 2009 - 11:25 AM.

[hystrix cristata]

It's got a dynamo and the horn has been replaced at some point with one of those newer plastic red ones. Im tempted to turn the battery round and see what happens but I don't want to break anything

[MRA]

if it has an alternator then i would say its positive earth also the lights may well be an earth problem, and the horn has not been used for so long that its knacked or just rusted

If it has an alternator it will ONLY be a negative earth

[hystrix cristata]

Anyone any more information on this. If it is positive earth how easy is it to change to negative earth

[zef]

Anyone any more information on this. If it is positive earth how easy is it to change to negative earth

Dead easy matey. Did that on my '69 Elf. Get a mini alternator and fit it, you may need some brackets for a good fit. If you have a dynamo then you'll have a voltage regulator in the engine bay. You make all the connections you need in that. Have a search there's info out there on how to do it. Oh yes and when you've done it make sure the battery is connected with negative to earth.

[miniman_7]

You don't need to change to an alternator to go to positive earth!
Obviously, doing so will mean a more reliable charging system.

Your haynes manual for the earlier cars should give details on setting the polarity of the dynamo (in my copy it is on page 181 in section 8; Dynamo - removal and refitting)
It says how to polarise to positive earth. To turn to negative, just reverse the wires.

Everything should wrk fine on the car, unless you have an old positive earth radio

[bmcecosse]

You should convert it to NEGATIVE earth! Alternators are almost ALL -ve earth (few early 11AC models were +ve) - and all modern radios etc are -ve earth. It also supposedly helps to cut down body rusting!! You can easily polarise the dynamo to run -ve earth. The other problems are not related to the earthing in any way.

[hystrix cristata]

cheers guys, someone on another forum has told me it doesn't matter which way the battery is it will still work. Been looking at a few wiring diagrams and the only difference I can see between -ve and +ve earth is which side the wire from the coil to the distributor is connected. It doesn't have a radio in but I am considering putting one in when I can work out where to put speakers etc so will turn the battery round and have it -ve earth just because it makes more sense to me. Been fiddling with wires and just the horn doesn't work which I think is a faulty horn after quickly testing it on my pickup and it still not working, that and ignition light stays on.

[bmcecosse]

Ign light stays on - probably because the dynamo needs re-polarising! Swap the battery around - and check the coil connections - and then take a lead from the main battery cable and 'spark' it onto the small terminal on the dynamo - do it a couple of times. This re-polarises the dynamo to the -ve earth running.

[taffy1967]

You don't need to change to an alternator to go to positive earth!
Obviously, doing so will mean a more reliable charging system.

Your haynes manual for the earlier cars should give details on setting the polarity of the dynamo (in my copy it is on page 181 in section 8; Dynamo - removal and refitting)
It says how to polarise to positive earth. To turn to negative, just reverse the wires.

Everything should wrk fine on the car, unless you have an old positive earth radio

Won't the heater fan need turning around? I've heard it'll rotate the other way after conversion and won't be as effective?

[dklawson]

Won't the heater fan need turning around? I've heard it'll rotate the other way after conversion and won't be as effective?

No, the fan will be OK as will the starter motor, 2" gauges, etc. The critical components are the dynamo itself (which as discussed above needs to be re-polarized) and any gauge like an early electric tachometer. If the car originally had an electric fuel pump that needs to be addressed also.

As a footnote to Roy's observation above about re-polarizing and the ignition light. Be prepared for the worst. If the car had been polarized for negative earth and the battery was connected for positive earth AND driven that way, there may be some damage to the control box or dynamo. I'm not saying there is damage, only to watch for it.

[Rosslin Racing]

if it has an alternator then i would say its positive earth also the lights may well be an earth problem, and the horn has not been used for so long that its knacked or just rusted

If it has an alternator it will ONLY be a negative earth

thats what i ment I should read my posts before putting them out.
100 lines with you tomorrow

[MRA]

Won't the heater fan need turning around? I've heard it'll rotate the other way after conversion and won't be as effective?

Wow does this mean that you have one of the few efficient Mini heaters then

[bmcecosse]

It does appear - from comments about heater fans on another forum - that indeed the heater may run wrong direction. I haven't noticed/tried this myself - but it may be worth swapping over the two wires to the heater motor to see if it seems to pump more air one way than the other. Interested to have some feedback on this - if anyone has time to try it out!