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Reversing light switch types
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colwyn500



Joined: 21 Oct 2012
Posts: 1745
Location: Nairn, Scotland

PostPosted: Tue Feb 11, 2020 12:49 pm    Post subject: Reversing light switch types Reply with quote

The switch I obtained for my gearbox is the correct thread and dimensions and is activated by the reverse selector-rod inside the gearbox. In neutral and any other gear than reverse, the plunger of the switch is normally depressed which closes the internal contacts and would provide a circuit to ground or to return a live feed.

When reverse is selected the selector-rod inside the gearbox moves away from the plunger of the switch and the contacts are open. This is the opposite (reverse Wink ) of what I expected as I have wired a circuit so that this switch would acivate a relay and supply a feed to the reversing light when reverse was selected. I presume I now need to obtain a switch that works the opposite way to this.

So I'm asking what is the terminology for a switch which when in its active position is normally open.....maybe I answered my own question?

Or is there a way I can make this setup work with the existing switch?
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alanb



Joined: 10 Sep 2012
Posts: 516
Location: Berkshire.

PostPosted: Tue Feb 11, 2020 2:27 pm    Post subject: Reply with quote

If the contacts open three can be no circuit , are you sure you are checking this correctly? Normally you have live to the switch and the lamp permanently earthed on selecting reverse the contacts are closed making the circuit.
There are 2 types of switches available those with contacts normally open and those with contacts normally closed. From your discription you would need a switch with contacts normally normally closed, i.e. Press the plunger to open release the plunger to close contacts.
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colwyn500



Joined: 21 Oct 2012
Posts: 1745
Location: Nairn, Scotland

PostPosted: Tue Feb 11, 2020 3:03 pm    Post subject: Reply with quote

alanb wrote:
If the contacts open three can be no circuit , are you sure you are checking this correctly? Normally you have live to the switch and the lamp permanently earthed on selecting reverse the contacts are closed making the circuit.
There are 2 types of switches available those with contacts normally open and those with contacts normally closed. From your discription you would need a switch with contacts normally normally closed, i.e. Press the plunger to open release the plunger to close contacts.


Thanks Alan. I am checking it properly but almost certainly not describing it or using the terminolgy correctly. But your answer clarifies what I've been thinking and now the job is to find such a switch which will fit the gearbox. Smile
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alanb



Joined: 10 Sep 2012
Posts: 516
Location: Berkshire.

PostPosted: Tue Feb 11, 2020 8:00 pm    Post subject: Reply with quote

What vehicle is this for? This company has a good selection,
https://tridon.com.au/products/Tridon/35/483/switches-and-sensors/2016/reverse-light-switches
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colwyn500



Joined: 21 Oct 2012
Posts: 1745
Location: Nairn, Scotland

PostPosted: Tue Feb 11, 2020 9:38 pm    Post subject: Reply with quote

alanb wrote:
What vehicle is this for? This company has a good selection,
https://tridon.com.au/products/Tridon/35/483/switches-and-sensors/2016/reverse-light-switches


Thanks for the link.

It's complicated. The vehicle is a 1969 Fiat 500. They didn't have luxuries like this, but the later Fiat 126 gearboxes had an end cover which is a straight swap and which is tapped in the right place for a switch; the gearbox internals, gear ratios and synchromesh apart, are identical.

So I bought the "correct" part from a specialist dealer and it's simply been used as a blanking plug for ages until I decided to rig up a light for use on night rallies. But armed with the "NC" info you helped me with and scrolling through the specifications at The Green Spark Plug company, who give very thorough descriptions and have a massive range in reversing switches alone, I discovered that the switch fitted to the Nissan Pajero/Shogun looks likely to solve my problem. Very Happy
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alanb



Joined: 10 Sep 2012
Posts: 516
Location: Berkshire.

PostPosted: Tue Feb 11, 2020 11:13 pm    Post subject: Reply with quote

Glad to have been of some assistance, I had a fiat 126 for awhile, I was given it by a work colleague for my son to play with when he started his vehicle engineering course at tech college, it wasn't street cred enough for him to use when he started driving so I bought him a mini and after a while I sold the fiat as it didn't get used. The proceeds went to the mini money pit.
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1252
Location: Nottingham

PostPosted: Wed Feb 12, 2020 11:34 pm    Post subject: Reply with quote

The terminology for switches is Normally Open (NO) and Normally Closed (NC) I have come across both with reverse light switches and if you have the wrong sort a relay can easily correct it
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