Lucas 12 volt regulator testing, repair and theory of operation

In this video I open up, examine, and repair an 1970's era voltage regulator made by Lucas Electrics of England. I discuss a little about theory of operation, the individual components, some basic checks you can make, and testing operation.

[@juslitor]

God created light, Lucas created darkness.

[@stuartosborne3013]

Thank you I learned a lot from your video. I’m trying to get the Triumph Tiger 90 charging system back into life. I guess this is the benefit of old style things they can be repaired.

[@johnpipping3848]

Same issue on my Ford tractor. I marked (just in case!) and turned the adjuster plate on top of the centre bobbin to put more load on the spring, (in other words used a wider diameter of the cam) and the voltage then increased to around 13.1V with the engine running at working speed. I reckon that's good enough, we'll see. If not, it's just €35 and 20 minutes fitting for a brand new unit, so no biggie.

[@DelTry-tq3fh]

Most excellent sensible and informative presentation. Thank you, from the uk, for taking the time to make this video.

[@damianbutterworth2434]

Sorry for over commenting but I used to set these up in a factory. I never could understand why you would need 2 regulator relays. I thought voltage would do and let the battery and load circuit be connected together. I might try and make one with an Arduino tomorrow with a DC SSR.

[@iulianc9037]

The letter D stands for dynamo

[@LukeSchiralli]

A very informative video, thanks for putting it together.

[@ianrobinson9565]

That is an RB 340 lucas regulator. Do you have all the electrical and mechanical settings in order to service it CORRECTLY?

[@stevewatr]

I think I found the specs online. It is charging the battery now, but there is a parasitic drain when parked with the key off. So I just remove a battery cable when parking it.

[@ianrobinson9565]

@stevewatr Three things to look at if you are getting parasitic drain. Check that the cutout in the regulator is opening. Check wiring on the key switch is not cross connected and Check the wiring in general. Look for rub throughs in the wiring. Parasitic drain can also be measured using an amp meter. It is a fairly simple system, but can be difficult if you are only working on it occasionally. CHEERS.

[@jabirucru6970]

I had the 1968 mg 1300 version and it may be my memory failing me but isn’t there a Lucas voltage regulator missing on the firewall or did they change it in later years???

[@dogpaw775]

Thanks, inspired me to go 'back in' and see if my mechanical regulator issue can be resolved.

[@tasmedic]

Thanks for your excellent description of how these work. I learned a lot. Despite your totally dissing Lucas, I see that your ancient regulator works just fine with no adjustment. Maybe an apology is in order?

[@stevewatr]

The jury is still out. It its charging, however, when the engine is off, and they key is off, there is a parasitic drain on the battery. I haven't had time to investigate yet.

[@markgilbert9930]

Replaced by educated sand.

[@buddyrojek9417]

Thanks, trying to solve the generator regulator problem of the soviet motorcycle in Ukraine, as I can't read Russian so looking at your concepts and apply to this . Thanks, my bike was working, now the light comes on so I will copy your cleaning methods ( I watched your generator video too. )

[@Flowing23]

👍👍