Introduction: Re-cycled Lucas Diagnostic Kit

It's my first Instructable, so be kind...

I run a small engineering workshop on the sunny island of Madeira. We work mainly on classic cars, and I am always on the lookout for rare old classic car tools to add to my collection, so when a bunch of tools popped up for sale, I snapped them up.

With these tools came a full 1970s (I think) Lucas Electrical Diagnostic set - complete with instruction cards. This comprises a set of three devices that indicate different voltage levels via three LED's and a bunch of instruction cards that you used depending on the problem with the car. I've had these kicking around for several years now, and I haven't the heart to throw them out, so the enforced workshop shutdown has forced me to tidy the office/electronics bench.

There are three little bits of test kit spring to mind as needed in the workshop:-

1. Dedicated Battery Meter (Yes, one of these is a battery meter, but I want a little more resolution than Good/Bad/Replace!)

2. Remote engine start - when I am tuning carburettors, it's very useful to have basically a box with a switch to crank the starter over to re-start the engine.

3. A continuity meter for the build-up area.

Yes, a Multimeter could be used for 1 and 3, but I'm getting tired of seeing my lovely expensive meter getting bashed in the workshop when all I want is an indication.


One old Lucas Diagnostic Kit - Although up-cycling stuff like this can apply to almost anything.

Soldering kit, solder, pliers, cutters, craft knife, file, and a bunch of old odds and ends.

Step 1: The "12V Battery Tester"

The Lucas "12V Battery Tester" simply has three led's to indicate:-

"Battery OK", "Recharge Battery" & "Investigate Battery"

While this could be useful, its far more useful to have an accurate voltmeter reading of the battery voltage.

I had a dig around in my parts bins, and foud some cheap and small digital voltmeters left over from a previous camper van project. These have an overall size of 14mmx22mm.

Firstly, I took the unit apart - I thought that the case was familiar - it's a Verobox case - standard enclosure - quite old now - I've not seen one on sale for a while. The circuitry was quite neat, but the old LED's were quite dim - the digital display is far brighter.

I realised that I could fit the digital display into the top of the case, and retain the original circuit as well!

I carefully cut the case back using a file until it fit perfectly. A word of advice here - go slowly and carefully when machining cases. The more time you spend, the better the finish will be - "Measure twice, and cut once". Plastic cases are easy to cut, so this doesn't take long, but still be patient - file a little bit and test fit, repeat as necessary.

The file could not create quite such a clean inner corner, so I fettled this with a craft knife.

By creating a snug hole, I was able to mount the meter only using an adhesive pad (the kind used to secure trim parts and number plates. This adhesive tape works best if it's heated up to reactivate the adhesive. I used a hot air gun to do this.

Wiring was simple - It was connected directly across the incoming tester cables.

What's left - a very neat little battery voltmeter that will live in the battery charging area of the workshop.

Step 2: The Remote Start.

When you are tuning carburettors, you often stall the engine. It's therefore very useful to have what basically amounts to a switch with long leads and crocodile clips, so you can activate the starter while fettling under bonnet.

SO - I used the aptly named "12V Starter Tester"

This also has three LED's - but all I really want is a case to mount a switch in.

I wanted to leave the LED circuit in, and it could illuminate to indicate that I had a voltage across the switch when the switch was not pressed. But, by cunning planning. I was not only able to fit a switch, but also another meter, so this remote start also has a digital meter.

The build was again straight forward.

Cut and file the slot for the meter as per the battery tester.

Drill and file the hole for the switch. (I found this switch in a scrap bin from my old career as an electronics systems engineer - I think it might have come from an earth moving machine?)

The meter was wired directly across the original two test leads, and the switch connects the new third lead to the +12V. This way, I can also monitor the car battery while I'm fettling - useful, because old car charging systems are less efficient than modern ones, and also often don't actually charge while idling, so it's nice to see if I'm letting the battery drop too much. "Lucas, Prince of Darkness"....

Step 3: The Continuity Tester

When we rebuild a gearbox or transfer box, we need to test the switches within it (reverse, high/low range, difflock, starter inhibit or neutral, depending on the gearbox). I decided to build this, so this tester can remain in the build area rather than drag out a multimeter.

I used the last unit - the "12V Alternator Tester"

This time, it was obvious that I would have to gut the insides. I want to use a readily available battery, so chose a 9v pp3 battery. (Actually, it's the only one I had handy!).

I would still need a board to mount the LED's to, so I de-populated (de-soldered) all the components from the board, and cut it down so I could get the PP3 battery in place, but still left a place to mount the resistor.

I used High Intensity Yellow LED's (again, what I had to hand from a car interior lighting project). These are rated at 2.0 to 2.4 volts 20mA max so I connected three in series, with a 220 ohm resistor to give me 15ma. The LED's are very bright and obvious - Perfect.

We regularly rebuild Land Rover gearboxes / transfer boxes, so this tester will have specific Land Rover connectors added later, as well as some small crocodile clips (Unfortunately, I have to buy some!).

Step 4: Results

Three useful little gizmos that will serve very useful in the workshop.

I'm a bit of a maker at heart, and I love re-purposing things, but I also love a little nostalgia, so this project is perfect. The fact that I managed to "Add" functionality rather than gut and start again brings out the little kid in me. It's nice to keep a classic "old school" feel with some of our kit, and repurpose it rather then creating more landfill - it also offsets the mode modern kit I use - 5 gas analyser, laptop based diagnostic sets etc,.

Yes, I could have used a bulb and battery for the continuity tester - but where's the fun in that!

A lot of old kit can be repurposed - even if it's just for the case! It can add an interesting dimension, or back story that you wouldn't have had if you had used a brand new case.

My next project is a portal Wideband lambda sensor kit, so I can monitor the fuel mixture on the fly - I removed an old scrap analogue cellular phone out of a car while we were upgrading it. I've just gutted it - it's the perfect size to mount an adruino, a power pack and support circuitry for the Wideband project - watch this space.

Step 5: What Did I Learn?

1. Writing an instructive is time consuming! It took longer to write up than it did to do! Good on you to all of those who write them to such high standards.

2. I need a better light over my workbench, I only have a high-bay light and an angle poise at the moment - the photos are rubbish!

3. I need to clean my workbench!

4. I need to plan before I cut (The battery tested has the meter in the wrong place!) Tut tut!

5. I actually had some fun doing this - it is nice to take some time out and let the inner kid play sometimes!

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