Classic cars forum & vehicle restoration.

MrWhite · Joined: 09 May 2017 Posts: 105

I have a car which was originally positive earth but has been changed to negative. Everything works, the Amp metre works in reverse but the radio and clock will be a positive earth and so don't work. Is there a way of getting them to work or do I need to replace them, which seems a shame as they are both fairly original to the car. I have to say I have managed to avoid the positive negative earth thing all my life so far, so I don't think I really understand Positive earth, my realisation of this came when someone mentioned fitting and ignition cut out (Old school security) and I then realised I wouldn't know how to do it.

Penman · Joined: 23 Nov 2007 Posts: 4755 Location: Swindon, Wilts.

Hi
With the clock and radio can't you just swap the wires over?
Put the positive wire to the negative terminal.
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47Jag · Posted: Mon Oct 23, 2017 2:34 pm Post subject:

Some older radios had a polarity switching plug which you moved to suit the car earth. Have a look for that. Otherwise it's easy enough to switch your car's polarity if it has a dynamo. It's a simple job to re-flash the field coils. If you reverse the leads as Penman suggests you will create a short circuit with the aerial wire. The clock I'm not sure about.

Art

47Jag · Posted: Mon Oct 23, 2017 3:46 pm Post subject:

If the radio is in any way transistorised it will more than likely be for negative earth. Some older radios had a polarity switching plug which you moved to suit the car earth. Have a look for that. Otherwise it's easy enough to switch your car's polarity if it has a dynamo. It's a simple job to re-flash the field coils.

Art

peter scott · Joined: 18 Dec 2007 Posts: 7118 Location: Edinburgh

DM · Joined: 21 Dec 2008 Posts: 212 Location: North Cornwall

One of these will do although it's expensive for what it is.

https://www.classiccarstereo.co.uk/accessories/autosound-positive-earth-adaptor/

Bitumen Boy · Posted: Mon Oct 23, 2017 8:00 pm Post subject:

I'd be surprised if a radio old enough to be positive earth would still work satisfactorily nowadays. TBH I'd think it likely to be ripe for replacement or conversion to modern internals.

ukdave2002 · Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire

Unless there is any reason to stay as negative earth.; simply convert it back Smile

Dave

lowdrag · Joined: 10 Apr 2009 Posts: 1585 Location: Le Mans

Riley Blue · Joined: 18 Jun 2008 Posts: 1750 Location: Derbyshire

Paul fairall · Joined: 17 Nov 2016 Posts: 429 Location: North west Kent

Me neither, if I want to listen to music I have a dedicated music room in the garden. Listening in a car with tyre noise etc is not my idea of enjoyment.
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1957 ford popular

Bitumen Boy · Posted: Tue Oct 24, 2017 3:04 pm Post subject:

Paul fairall · Joined: 17 Nov 2016 Posts: 429 Location: North west Kent

For many years I sat in traffic jams going into London, I guess those that still endure that have time for listening then. Everyone should make time for relaxing or doing what they love otherwise what is the point of living.
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1957 ford popular

kevin2306 · Posted: Tue Oct 24, 2017 8:08 pm Post subject:

When I bought the restored Motorola 828 for my singer, I had a lead fitted so I can use it with my iPod. Love music when driving,more so in my modern.

Kevin

MrWhite · Joined: 09 May 2017 Posts: 105

Thanks for your replies, lots of ideas, so that's good. I am not sure what happened with the car as we didn't have it for a while and it was positive earth when we had it before but now negative earth and the advive we were given was to leave it as it is. I should maybe have asked more questions about this but at the time I just thought Negative earth is more what I am used to, so it should make things easier, less likelyhood of connecting anything up the wrong way. I will have a look at the items and see if there are any switches, that almost seems too easy. I did read about "Flashing" but I have no idea how you do this (electrically of course) or what it actually means, so I wouldn't mind an explination of what to do or a pointer in the right direction. I think I probably still prefer to keep the car Negative earth, the more modern radio or the converter box are great ideas but I think just a wee bit on the expensive side. I doubt I will listen to the radio much but I do like music in the car (modern car usually), mainly I just don't like having things that don't work Rolling Eyes