lights dimming

[gmorry]

Hi anyone help with lights dimming problem I notice last night as I pit on windscreen heater my dash and front light where flickering but when I switched it off flickering stop it only happen with this switch any ideas?

[insanitybeard]

Are you talking about the heated front windscreen? Heated front windscreens use a lot of power and it isn't unusual to see (e.g) headlamps dim slightly or the blower speed reduce a little when it's switched on. If it's really apparent though it could indicate (among other things) that your alternator or battery aren't in the best of health (a charging problem) or the alternator belt tension isn't brilliant or the belt has seen better days.

[gmorry]

Thanks will check battery put new get on 2 months ago so how do I check alternator and tension wheel😊

[insanitybeard]

If the belt was loose I'd expect you'd hear it squealing with the engine running and especially if you have a lot of electrical systems turned on (heated screens, headlights, blowers etc), just make sure it's not slack by seeing how much it deflects when pushing it with your fingers (engine off obviously!). You can check the alternator output by putting a voltmeter across the battery terminals with the engine running, it should normally be about 12.5V or over with the engine running.

It is possible though the alternator is working but there's an internal fault with either the regulator or rectifier circuits causing the power fluctuation you are seeing, in which case it'll either be a replacement unit or a repair if you can find somebody able to repair the unit.

One other thing I'm not sure of is if the Mk1 Galaxy's have one way clutches on the alternator pulley. I'm inclined to say not on the Mk1 but I may be wrong. If it has, these can cause problems.

[Mirez]

Sounds like you have a diode either blown or on the way out on the the rectifier of the alternator. Your alternator therefore won't be producing DC but more of a pulsed DC as it misses one half of the sine wave. Unless you have a volt meter that has a fast refresh you probably will still measure 12+ volts.