Electrical problems 1961 Mk2 manual with OD

I’m chasing electrical problems on my car as above.

  1. where physically does the map light go?, mine is missing and I have obtained a new one but can’t find the purple/ green wire which feeds it. The wire from the switch goes into the loom but where does it come out again to connect to the light.
  2. the car was originally positive earth with Dynamo but has been converted to alternator with negative earth. All works ok and charges fine but I see from the circuit diagram that originally the Dynamo charged the battery via the gauge so that you got a true reading of current flow. Is there a way to wire the amp gauge with the alternator to do the same thing? It presently reads permanently a discharge though the battery is charging fine. The PO had wired the gauge backwards to show permanent charge I suppose because it’s more comforting.
    3 None of the instrument lights work nor do the lights on the label rail, I suspect the switch which I’ll get to tomorrow. All external lights work fine as do indicators.
  3. interior lights all work on the door switches but the interior light switch doesn’t do anything, again could be just the switch.
    Everything working via the two fuses works ok so they seem fine.

Any suggestions and help with position of map light much appreciated.


I think the bulb holder for the map light is on the underside of the top fascia capping. I think there are only 2 fuses in the Mk2 system, so, if one goes out, it takes a fair bit with it.

The interior lights are all fed from the same fuse and the four door switches and panel switch are wired in parallel, feeding earth to the lights. If the door switches work but not the panel one, you are correct, either the switch is faulty, or its earth connection. WRT the ammeter, early cars fitted with negative earth and alternator still used an ammeter, which, I assume was wired similarly to +ve earth cars. Later cars replaced the ammeter with a" battery condition" meter, which is a voltmeter, I believe. Unfortunately, I don’t have a wiring diagram for a -ve earth car with an ammeter, so can’t assist there, but it certainly can be made to work like it should. Someone with an S1 E. 4.2 or 420\ Mk10, might be able to help.

Hi Kevin
Thanks for the information, do you know which side of the dashboard the map light connections go to? My car is LHD and if I knew which side, dash or glovebox the wiring comes out of the loom on it would save me from having to de mount both sides. The dash top I removed today and there are no signs it ever had screws for the dash light, maybe a replacement dash top and I can’t see the two wires I assume come out of the wiring loom.
As for the ammeter wiring, I see that the spec for the alternator fitted is maximum output 90 amps so probably not a good idea to charge the battery through it. Ok in most instances but not if the battery were flat. I might try to source a voltmeter instead.

Hi Ian,
IIRC, the lamp holder was on the underside of the top rail, directly above the centre panel, so the wires for it poked directly out of the wiring loom at that point. Should be able to see them by swinging down the centre panel. Surely the alt doesn’t put out 90 amps? If you’re sure, it may be better to fit a voltmeter, but I’m sure the ammeter can be made to work, depending on the wiring of the alternator.

Hi Kevin
In my car the map light switch has a red wire in (12 v) and a purple green wire out which goes immediately into the wiring loom right above the switch. The loom is new. That must mean that somewhere else in the loom the pg wire comes out to go to the lamp probably with the black earth wire required to make the lamp function. I can’t find those wires out of the loom. I suppose I could just take off the wire into the loom and make a short two wire loom directly to the lamp but given the loom is new I’d like to do it as it should be if I can nit picky I know but that’s me. As for the alternator output current, it was bought and fitted by P.O. but the description on the invoice is 90 A. alternator.

Thanks also for the clue to how the alternator conversions were done to continue to use the ammeter. I found info on a Moss Motors description for their conversion via an MG site. I might try to wire in the alternator via the ammeter and if it doesn’t like it because of excess current, then switch to a voltmeter.
Great frustrating fun chasing lots of small faults, none of which stop the car from running but I like everything to work as it should. Next things to tackle, low speed on the wipers, slow speed on the heater fan and a hisser which doesn’t hiss even though the solenoid works ok. Not sure there’s petrol getting to it from the front carb.


Correct with the colours, red, purple\green and black earth. I agree with not modifying the loom if possible.

Problem with dash lights proved to be switch which was badly internally corroded but which can be disassembled and cleaned easily. Now done and working fine. Problem with interior light switch proved to be missing earth and wiper and fan slow speed non functioning also turned out to be switch related. All now working. On to the hisser problem. Thanks for the help.