18 replies to this topic

[JXC Mini GT]

My mini has a positive earth, is anyone aware of a supplier that could provide a toggle switch with a combined LED to suit a positive earth car.

[nicklouse]

Any just wire it up the right way round for the LED to work.

[weef]

For the LED to operate you have to wire the vehicle positive to the positve switch terminal and likewise the negative, but you have to realise the output from the switch will be a positive i.e. an earth. 

This somewhat complicates the wiring as normally it is the power feed that is switched, not the earth.

As I see it your options are

 

Convert the vehicle to Negative earth.

Convert the vehicle loom to switch the earth, really a non starter.

Find a switch that uses a convential bulb for illumination.

Use the LED switch output to operate a relay, then use the relay to operate the circuit.

 

If you want to keep the vehicle Positive earth then I would go for the relay option,  fitting relays to switch loads is quite a common practice and there is plenty of information available to do this work.

[nicklouse]

You would be surprised to know many modern cars are actually earth switched. Can be fun fitting horns.

[weef]

Maybe on a modern vehicle but we are talking about an older positive earth vehicle here where the o

[68+86auto]

You would be surprised to know many modern cars are actually earth switched. Can be fun fitting horns.

Not just modern ones, there were old ones that used earth switched headlights.

[68+86auto]

If you can show us an example of a switch you want to use we can see if it can be used. Not all illuminated switches will be wired the same.

[IronmanG]

Try David at wired by wilson

[KTS]

For the LED to operate you have to wire the vehicle positive to the positve switch terminal and likewise the negative, but you have to realise the output from the switch will be a positive i.e. an earth. 

This somewhat complicates the wiring as normally it is the power feed that is switched, not the earth.

As I see it your options are

 

Convert the vehicle to Negative earth.

Convert the vehicle loom to switch the earth, really a non starter.

Find a switch that uses a convential bulb for illumination.

Use the LED switch output to operate a relay, then use the relay to operate the circuit.

 

If you want to keep the vehicle Positive earth then I would go for the relay option,  fitting relays to switch loads is quite a common practice and there is plenty of information available to do this work.

 

there is another option which would be to run a connection from the earth tag on the switch to a point in the loom that has a battery -V connection (fusebox, regulator?)

[JXC Mini GT]

Thanks for all the suggestions, I will have a look at whats involved in converting it to Negative earth however the car is fitted with a positive earth Dynamator.

Edited by JXC Mini GT, 14 November 2023 - 11:59 AM.

[weef]

The dynamo will just need repolarised to negative earth, a straightforward process.

All you need to do to polarise the dynamo is to touch the dynamo field terminal with your chosen power feed, is this case the battery positive, a couple of times and the job is done. There is no need to remove the dynamo to do this.

[nicklouse]

Ok the switch has three terminals?

 

 Two need to be positive and one needs to be negative. Forget about thinking positive earth or negative earth.  Just wire it up negative to negative and positive to positive.

[JXC Mini GT]

The dynamo will just need repolarised to negative earth, a straightforward process.

All you need to do to polarise the dynamo is to touch the dynamo field terminal with your chosen power feed, is this case the battery positive, a couple of times and the job is done. There is no need to remove the dynamo to do this.

The dynamo has been changed to a Dynamator (Alternator that looks like a dynamo) I don't know about the wiring that's been altered to fit it, other than there are 2 types of Dynamator, 1 for positive earth and one for negative earth, they cost about £400 so I am reluctant to change polarity.

Edited by JXC Mini GT, 14 November 2023 - 08:30 PM.

[JXC Mini GT]

Ok the switch has three terminals?

 

 Two need to be positive and one needs to be negative. Forget about thinking positive earth or negative earth.  Just wire it up negative to negative and positive to positive.

I will have a play tomorrow with the wiring to see if I can get the switch LED to illuminate by switching the earth as you previously suggested.

[nicklouse]

 

Ok the switch has three terminals?

 

 Two need to be positive and one needs to be negative. Forget about thinking positive earth or negative earth.  Just wire it up negative to negative and positive to positive.

I will have a play tomorrow with the wiring to see if I can get the switch LED to illuminate by switching the earth as you previously suggested.

 

Just to clarify my thoughts. The switch has a feed + an earth - and a load. Simple on a neg earth car. But the load can be seen as an earth - as it has to make the circuit. 
 

on a + earth car your feed needs to be your  load earth +   But both your other two need to be on the feed - side .

 

further thoughts need me to get wires out as I think I can see a problem. Might have to pop back into the garage.