Motoroia 114 converter from Pos to Neg Earth

[Frampty]

I have a Motorola 114 which I will get converted to accept FM and Bluetooth but the conversion only uses Negative earth. Has anyone used an electronic converter from positive earth to negative earth for the radio.

[Lotus54]

If you ‘float’ the radio it will work just fine - just keep + and - as on radio.
But make sure nothing on the radio touches any earth on the car, like antenna etc. No part of the radio frame or connections can touch any earth/frame of the car.

I’ve done this in the past and it works just fine. But certainly have to be careful on how you mount it.

[Frampty]

Thank you

[Elanman99]

There is a real risk with floating the radio. Basically the metalwork of the radio (including it front control panel) will be connected to battery positive do any inadvertent shorting out, by say an unwary passenger with something like a charm bracelet.

Converting (the car) to negative earth is really very simple. Is there any particular reason you can't do that?

Ian

[Billelan]

Hi. I’ve used one of these polarity converters, not on an Elan, but on a steel bodied car where insulating (floating) the radio would have been too risky. It was compact, easy to fit and worked really well.

[Andy8421]

Bit of confusion in the posts above.

You do not need to 'float' the radio. The radio needs a +12v supply relative to ground (the negative connection, usually the body on a steel bodied negative earth car).

In the case of a positive earth car, there is no +12v supply relative to ground, only -12v.

To solve this problem, you could use an entirely separate battery to generate the +12v supply relative to ground the radio needs, but it is easier to to use a DC to DC converter. The radio case will remain at ground potential as will the antenna lead and antenna base.

This supply will be at +24v to the other cabling under the dash, but if fused and installed appropriately shouldn't present too many additional risks, certainly better than having the case of the radio 'live'.

[Elanman99]

My post added to the confusion, I knew what I was trying to say but certainly did not put it very well.

My concern was having the radio casing not connected to the same ground as the rest of the car and I agree a polarity inverter solves the problem (not that I have seen anything for sale labelled as such).

Still I think simpler to convert the vehicle to negative earth.

Ian

[Andy8421]

My concern was having the radio casing not connected to the same ground as the rest of the car and I agree a polarity inverter solves the problem (not that I have seen anything for sale labelled as such)

Ian

Ian,

A bit of a boat anchor, but here you go:

https://www.ebay.co.uk/itm/326119597118?itmmeta=01HXVBMWEDFBCB02ZR3C1AK5CV&hash=item4bee3e243e:g:OVMAAOSw171kxh6~&itmprp=enc%3AAQAJAAABAMfonnM%2FPSmZBK%2BUHB8c4OHERjJStZNByGYQAXITl%2BUXXqTpyBI2sjH4Cs5Ng5725XvIrSViBp4%2B8Hl%2FmJDI0IE%2FK5BJqABJWil5UoGD2sGiIbnIZk00E37ZHlSsciKCjUg6kG31qnKVuv9dOxIPiz20t6LFvGL3Z6fIQQU1Wyz1tLbMf0WM4ktEwSEX2iWBDOTo6D2cfU6xnPCTB4fjkMNACzlt486FeLlnVkOy3qjM87mzlCzOFUwS%2FA9eEDzj8WIxVfpvfIGtAaZCmyjZe%2BJJY9WKBtymXIf2YYve3AtPglWskY6Ka5ufGMyefDxO6Dkz3QVNKQXHjBFEww0aj04%3D%7Ctkp%3ABk9SR6bH0-vuYw

Though should the OP have any electrical skill, googling 'Isolated DC to DC converter' will bring up 100s of possible candidates. Converting the car to negative earth is straightforward, but will require the rev counter to be swapped over as well,