Classic cars forum & vehicle restoration.

[ukdave2002]

It must be the month for 6v charging trouble's!, If you are having a problem at night with your 6v electrics this may may help..

A work college has just acquired a nice series 11 Morris 8, all is fine except that when driving at night the battery is discharging. He brought it round yesterday, I was expecting to fine a duff bit of wiring or control box that needed adjusting , did the usual checks, generator was fine , voltage cut off all fine, yet wont charge the battery with all the lights on. So I am now looking for a fault, no joy as again everything checks out ok.

So I then did a quick calculation of what the electrical load was so that I could compare to what was being drawn, this is the breakdown

Headlamps 2 x 36watt bulbs, requires 12 amps
Side lamps 2 x 5 watt bulbs, requires 1.6 amps
Tail lamps 2 x 5 watt bulbs, requires 1.6 amps
Ignition requires 2 amps

So total to run the car with lighting requires ;17.2 amps.

The spec for the dynamo fitted (Lucas C45N) is 6.5v 14 amps max at 2000 rpm, so we are over 3 amps short, and this is not allowing for charging the battery and using indicators, wiper motors etc. The dynamo is the correct unit for the car, surely Morris would not design such a flaw!

After a bit of digging in the operational manual, things became clearer. The original spec for the bulbs was as follows;

Headlamps 24 watt (it had 36w)
Side lamps 3 watt (it had 5w)
Tail lamp 3 watt (it had 5w), and there was only 1 rear tail lamp originally, but like many cars at some point a 2nd has been added.

The total “original” load would have been about 5.5 amps less than the current load, which the dynamo could have coped with. Problem is that I don’t think you can buy (or would want to fit!) 24 watt headlamp bulbs any more. The only solution was to fit a upgrade; I hada Lucas C45YV which has a higher output than the C45N, and delivers it at lower revs, but looks identical. Even this unit is only just adequate so he will have to keep the charging system in good nick, and forget any ideas about fitting a sound system.

Dave

[Rick]

Very interesting, amazing how a minor mod like fitting slightly different headlamp bulbs can cause things to go awry!

R
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[Uncle Joe]

Yes, I agree with you Rick.

UK, I find your electrical topics fascinating.

The one thing I always wonder though, why dont people convert to 12volts? It would save a lot of trouble in the long run...