i have a problem
when i turn the lights on in the old 1200
it idles rough
any help would be good

i have got a new alternator but still on good

If its external reg the reg could be out of adjustment, Bad earths??

battery weak and lights taking up to much power and not letting the fuel pump give the engine enough fuel?

internal reg, bad earth ?? is this to the lights
mec fuel pump, try new battery and had same proplem

any one

Have you checked power to the coil when the lights are on? Thats all I can think of right now, weak spark.
The headlight circuit has always been the weak link in the 1200's electrical system.

dont forget the windscreen wipers too levey, another weak link in the electrical circuit

Chuck a volt meter on the battery and check what the reading is at idle with lights on and off. Should stay reasonably constant at approx 14.5 volts, this would indicate the alternator/regulator is OK?

Battery cant hack the current drain. Alternator under load creates more load for engine. Also spark is not as good. All cars do it to some extent.

You need to clean up headlight connectors and main harness connector that feeds engine bay from fuse box. also cleanup earth points that goes under horn relay mounting screw. Wipe vaseline over the top to stop further corrosion.

Replacing headlights comes next, nut it's more likely due to dirty connectors in the loom or on the fuse box. I reckon 70% of under dash wiring looms I've seen/collected over the years has some melted connectors in the main feed or the wires that plug into fuse box due to and corrosion buildup.

thanx will try on monday