Automatic dimming head lights

[Theo_NL]

This feature has installed itself in my car

Driving it in the dark yesterday for the first time since long, I experienced following:
At random the head lights AND the speedo light AND the warning light for flashers (if in use) lights up significantly. Like switching from 12 to 15V... It randomly switches back to the 'normal' level. Or the other way around (normal level is not that much, but never had been better). Happened approximately 15 times on a trip of 40 minutes.

Where should i start to solve this?

[simmitc]

Perhaps it is jumping to 15 volts - check the regulator output.

[bmcecosse]

If it's a dynamo - I guess it's jumping in and out of charge........ Look for bad connections/worn brushes - and check the Regulator....

[Theo_NL]

Sorry, forgot to mention: Alternator fitted, no voltage regulator.

[bmcecosse]

Unless the belt is slack.....faulty alternator...... Which may of course simply be stuck/worn brushes....

[kennatt]

would think its the control unit inside the alt. available via EBay and easy to swap,have a look on U Tube for how to do it Assuming ACR alt.Dosen't need soldering only need small sockets to get covers off.Think the one I got was about£8.

[bmcecosse]

Bit unlikely that would go ON/Off though - unless a bad/loose connection. The outer brush wears much more than the centre one - try new brushes first...

[kennatt]

the one I had Roy was on an mgb and was axactly the same in fact it used to blow side light bulbs with the high voltage,fitted a new unit, fine after that ,but yes could be simply brushes.but if brushes would'nt it be dropping volts and rising to 12 or 13,as it worked correctly not going from 12 to 15,or would it

[bmcecosse]

Well 12 is the 'off charge' volts - and 15 could be volts if it cuts in and the battery has run down and needs a charge.

[Theo_NL]

Update

I fitted a temporary voltage gauge and made a test drive.

[frame][/frame]

Immediately after starting it went thru the roof, up to 19V. 5 seconds later to a steady 13.6 volt at cruising speed and 13.4 at idling. During the 10 minutes trip it went up to 17+ volt 2 times for a couple of seconds.

I bought me a new alternator (made in China, I know.... ).

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It is giving me a steady 14.2 Volt (driving) and 14.1 at idle

Learned from this forum these new alternators are not expected to survive for long, I intent to repair the old one for spare. I guess the small regulator (?) box in the alternator is broken, see picture below. I tried, but could not find it at the known suppliers. Anyone knows where to get it?[frame][/frame]

[MrIan]

They're on good old Ebay starting from about £5 inc post. No idea on the quality though.

[Trickydicky]

Here is a supplier, don't know if they will ship outside uk?
http://www.jcrsupplies.co.uk/products/A ... UILD_PARTS

[bmcecosse]

The original looks like a Lucas ACR ? In which case -spares should be available ok.

[Theo_NL]

Here is a supplier, don't know if they will ship outside uk?
http://www.jcrsupplies.co.uk/products/A ... UILD_PARTS

Thanks for the link!

Looking at my problem (frequent increasing of the voltage, and dropping back to normal) which parts might cause this? (electronics is not my expertise)

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[bmcecosse]

Just get the complete kit! http://www.ebay.co.uk/itm/LUCAS-ALTERNA ... 2a25ef3d20