Lucas PRS8 switch

Hi All,

I got a brand-new so-called "genuine" Lucas PRS8 ignition & light switch from a reseller, but it's simply rubbish. I sorted the problem with the ignition key by feeding the ignition directly from the battery (12 volts) with a ON-OFF switch, but I have no solution to fix the transient lighting problems.

Does anyone know what other reliable switch I coud use?

It's for a 1960 Dommie (with the big headlight shell). I am not looking for the original design as long as it works!

Thanks!

Laurent

Besides being a key operable switch, the switch serves two purposes:

1) lighting
2) stator control

Lighting function is OFF - PILOT - MAIN
This function can be done with a double pole double throw (DPDT) switch (10A)

The stator function can be accomplished with a second single pole double throw (SPDT) switch. Alternatively, you can bypass the lighting/charging switch by wiring the stator leads directly to an electronic regulator/rectifier such as a Podtronics.

I am not a purist .... when my Lucas switch crapped out, I replaced it with two rocker switches having a center off position. See below.



The left switch is lights PILOT - OFF - MAIN, the right is Stator OFF - OFF - ON. The right switch can be eliminated by wiring direct to a Podtronics or other regulator/rectifier, or with some modifications, the original 3 wire stator LOW - MID - HIGH amps can be accomplished. In jurisdictions requiring Lights On, the Stator Off becomes superfluous ....so eliminate it and let the regulator control the stator.

You could probably work this wiring diagram into your Dommie:



PM me if this scheme fits your needs and you need more info.

Slick

Thanks a lot Slick. Quite helpful!

I think I will go your way, but without the alternator switch. My alternator is directly connected by 2 wires to the Regulator-Rectifier, and I don't need to use its supply to cope with a flat battery (as I understand that in your solution, the alternator switch is the equivalent of the EMERGENCY position of the ignition key on a Lucas switch).

Rgds,

Laurent

@laurentdom

If a rocker switch is not to your taste, you can use a rotary DPDT in the hole where the Lucas should go.

With your 2 wire stator already connected to the Reg-Rect, the Lucas PRS8 is functional over-kill for lights only. I would use a good quality rotary 10A switch and get simplicity and reliability. Digi-Key (http://www.digikey.com/) is a good on-line source for electrical components.

You may want to opt for a water-proof switch version. My rockers are not water-proof, but I have never had a problem despite being caught in the rain and soaked to my skin.

Slick

Oops! You will need a double pole 3 position rotary switch to achieve a center OFF position. Then wire per the diagram in my previous post.

The new PSR8 switches are pattern copies and are NOT up to standard. If you want the ability to start with a flat battery install a 2Mc capacitor, this will also (at a pinch !) allow you to run with no battery.

norton bob said:

The new PSR8 switches are pattern copies and are NOT up to standard. If you want the ability to start with a flat battery install a 2Mc capacitor, this will also (at a pinch !) allow you to run with no battery.

Click to expand...

Don't they run a Maggie as mine does 1960 650 Manxman.

Ashley

Nope, Bikes fitted with the PRS8 were all coil ignition. Pretty well most of the twins made in 1960 were coil. Mag bikes used a simpler switch.