Tech Tip: Lucas 30608 Ignition Switch - Understanding 3 & 4 Spade Terminals

At some point during your ownership of a vintage motorcycle you may encounter that your original Lucas ignition switch may need to be replaced

Usually a failed ignition switch is caused by vibration, moisture and from "installing / removing" your ignition keys "in and out" over the years which will eventually wear your tumblers

If you wait long enough to replace a known bad or failing ignition switch, you may find yourself stranded on the side of the road! 

Although most know the basic function of the Lucas 30608 ignition switch, some folks are not aware that the new Lucas and EMGO 30608 ignition switches are slightly different from original Lucas switches 

If you are in need of a replacement ignition switch or you already have a replacement switch on hand from us you may find that your spades have a different terminal count and may confuse you

In today's Tech Tip post we will cover the main differences from original and new switches on the market

Keep reading the post below and follow along! 

The switches 

Before we dive into this topic, lets showcase 3 Lucas 30608 ignition switches commonly found on most late model Triumph, BSA and Norton marks along with vintage British vehicles from approx 1966 and later..

Above we have 3 types of Lucas 30608 ignition switches

From left to right 

• Left (original Lucas) - 3 prong
• Middle (new Lucas) - 4 prong
• Right (EMGO) - 4 prong

As you can see all the switches look fairly the same minus the style of key head, finish, etc

The main feature most noticeable when installing a new Lucas or EMGO switch is that there are 4 spade / prong's rather than 3 spades like the original Lucas switches as shown above in the far left..

For the most part, all new Lucas and EMGO ignition switches will replace Lucas 30608 and also other associated old and new superseded part numbers ...

Common part numbers

Since the Lucas 30608 switch is common on most models the "new" Lucas and EMGO switches will replace some of the following original parts numbers..

• 19-1775
• 99-0558
• 31899
• 03-3016
• 31886
• 60-0989

 I'm sure there are more part numbers out there, above is just a small few (you get the idea)

Spades / terminals 

The main question that we get from customers when replacing an old Lucas ignition switch with a new Lucas or EMGO switch is:

• "I purchased a new Lucas 30608 switch and noticed it has 4 prongs and not 3 like my original, will it make a difference?"
•  "What does the 4th prong do that my original Lucas switch did not have?"
• "Do I need to send this switch back for a 3-prong switch?"
• "Which spade do I hook my wires up to?"

 To answer your question in a straightforward manner the answer is the new 4-prong 30608 switch will work and replace all 3-prong ignition switches

Both units (3 and 4-prong) feature a 2 position setting.. “on and off” as fitted to most models from approx 1966 and on

 The reason why Lucas and EMGO brands are producing a 4-prong switch is for "universal" applications 

It is more efficient to produce 1 switch to replace 5 or 6 variations that where used over the years rather than making 5 or 6 difference switches when in reality they are all same 

In other words, the 4-prong ignition switch is a better choice and replacement part 

Installation

If you have an original Lucas switch for reference (and replacement) you can mark each terminal #1, #2 and #3 and simply transfer your old wires to the new 4 prong switch in the same sequence

Internally the switches are same, so don't let the 4th prong confuse you!

Most motorcycles do not use the 4th spade terminal so you can leave it "as is" or simply put a cap or block on the end of the spade (your choice) 

If you do not have an original switch to copy, get out your multimeter in the ohms setting and start checking continuity between each spade terminal to figure out which wire belongs in the proper location

Need a new ignition switch?

Should you have an original Lucas switch that needs to replaced we have 2 new types of complete ignition switches that are ready to be installed 

Click on the links below to purchase your new switch 

Recap

 The next time you are in need for a replacement igniting switch do not let the 4th terminal trick you!

It's the same switch with an added terminal for "other" applications 

Install the switch as per your wiring diagram or how your machine was originally wired and all will work and function well

Thanks for reading

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Ride safe! - Classic British Spares