xsspeed Posted November 3, 2009 Share Posted November 3, 2009 Is someone able to enlighten me or point me in the direction of some credible info pertaining to negative ground electrical systems and/or how this differs from the norm? I am a n00b wrt this Reason I ask is I have acquired some old car electrics including stereos etc, that say "For Negative Ground Only" and either 12V or 13.8V. Quote Link to comment Share on other sites More sharing options...
KKtrips Posted November 3, 2009 Share Posted November 3, 2009 Positive earth means the body is connected to the chassis and Negative earth is the opposite Almost all vehicles are negative ground - only fools with positive ground vehicles on this site would be Torton and borgweiser A alternators voltage fluctuates between 12V and 14.4V so if you have a stereo that has between 12V and 13.8V and is negative ground - I would be quite confident you will be safe with the vast majority of 12V cars unless you have something British from the 60's or earlier.... Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2009 Share Posted November 3, 2009 KKK is correct. Plug it in Quote Link to comment Share on other sites More sharing options...
KKtrips Posted November 4, 2009 Share Posted November 4, 2009 Positive earth means the battery positive is connected to the chassis and Negative earth is the oppositeAlmost all vehicles are negative ground - only fools with positive ground vehicles on this site would be Torton and borgweiser A alternators voltage fluctuates between 12V and 14.4V so if you have a stereo that has between 12V and 13.8V and is negative ground - I would be quite confident you will be safe with the vast majority of 12V cars unless you have something British from the 60's or earlier.... fixed - doh Quote Link to comment Share on other sites More sharing options...
mikuni Posted November 4, 2009 Share Posted November 4, 2009 Almost all vehicles are negative ground - only fools with positive ground vehicles on this site would be Torton and borgweiser I may be incorrect here but aren't early Fords (Mk1 Corts + Scort) positive earth due to generator stz? Quote Link to comment Share on other sites More sharing options...
xsspeed Posted November 4, 2009 Author Share Posted November 4, 2009 aha your second post of clarification makes sense. Cheer ears. Yeah the warning for Negative Ground threw me off eh, 1st time I have seen a warning label about it on something electronic so thought I better play safe. (this one stereo in particular appears to be around 15 years old or so). Quote Link to comment Share on other sites More sharing options...
Ned Posted November 4, 2009 Share Posted November 4, 2009 To be safe, connect a multimeter up to where you are about to run the stereo from and have a look Quote Link to comment Share on other sites More sharing options...
tortron Posted November 4, 2009 Share Posted November 4, 2009 actually the morrie has been converted at some point to negative earth just need to flip the battery around re-polarise the starter seem to recall changing the wires on the fuel pump and coil. dunno why it was done tho - i have 0 electrics. supposedly negative ground doesnt promote as much corrosion Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 4, 2009 Share Posted November 4, 2009 supposedly negative ground doesnt promote as much corrosion If that was true then I would need an explanation before I was convinced.Positive earth is a PITA Quote Link to comment Share on other sites More sharing options...
tortron Posted November 4, 2009 Share Posted November 4, 2009 galvanic electrodes and some such Quote Link to comment Share on other sites More sharing options...
CaMpylobacter Posted November 4, 2009 Share Posted November 4, 2009 yuh my id has een changed too. you change the coil leads, and repolarize the GENERATOR. starter it doesn't worry it. also, if you have an ammeter instead of a charge light, swap the leads on that bad boy. my ammeter runs backwards. lol Quote Link to comment Share on other sites More sharing options...
tortron Posted November 4, 2009 Share Posted November 4, 2009 yuh my id has een changed too. you change the coil leads, and repolarize the GENERATOR. starter it doesn't worry it.also, if you have an ammeter instead of a charge light, swap the leads on that bad boy. my ammeter runs backwards. lol dammit i ment generator Quote Link to comment Share on other sites More sharing options...
CaMpylobacter Posted November 4, 2009 Share Posted November 4, 2009 /fit alternator instead/nah genneys are way mean, esp combined with crank handle. Quote Link to comment Share on other sites More sharing options...
Hemi Posted November 4, 2009 Share Posted November 4, 2009 guy what was that old car outside the cafe we saw on sunday morning? was mean . anyway shit should be positive earth , if i heard right from my auto elec tutor diggers are like that to stop electrolosys Quote Link to comment Share on other sites More sharing options...
forced Posted November 4, 2009 Share Posted November 4, 2009 You don't change the coil leads. If you do then it won't work properly. SU type fuel pumps are solenoid operated so you don't change them either. It's got nothing to do with galvanic or whatever. Going back , most things were positive earth, that's how all the old (valve) radios are made. Or to put it in other words, in the days prior to the transistor, electronics were easier to make in positive earth due to the way that thermionic valves work. Even today, telecom exchanges are still positive earth. Electrolysis is only relevent if the machine is earthed, like a boat for example. Rubber tyres are a good insulator but caterpillar tracks aren't. As far as electrolysis goes on a digger,it's probably irrelevent. More useless info. Steve Quote Link to comment Share on other sites More sharing options...
Hemi Posted November 4, 2009 Share Posted November 4, 2009 You don't change the coil leads. If you do then it won't work properly. SU type fuel pumps are solenoid operated so you don't change them either.It's got nothing to do with galvanic or whatever. Going back , most things were positive earth, that's how all the old (valve) radios are made. Or to put it in other words, in the days prior to the transistor, electronics were easier to make in positive earth due to the way that thermionic valves work. Even today, telecom exchanges are still positive earth. Electrolysis is only relevent if the machine is earthed, like a boat for example. Rubber tyres are a good insulator but caterpillar tracks aren't. As far as electrolysis goes on a digger,it's probably irrelevent. More useless info. Steve so people with those things hanging down behind their cars are douches? also im pretty sure ign coil only work one why chap ... the positives exit at the same point Quote Link to comment Share on other sites More sharing options...
Ned Posted November 4, 2009 Share Posted November 4, 2009 so people with those things hanging down behind their cars are douches? also im pretty sure ign coil only work one why chap ... the positives exit at the same point What are they for? i was told once that they were to ground the car for if they got struck by lightning... Never had a reason to doubt it because i didnt really care but now i'm curious Quote Link to comment Share on other sites More sharing options...
tortron Posted November 4, 2009 Share Posted November 4, 2009 to prevent static shocks also The procedure for changing over to negative earth is very simple. Most people do this when they want to fit a modern radio as these are polarity conscious.1. Switch off ignition 2. Disconnect the battery and turn it round the other way. Cut two 'U' sections from the metal bracket that retain the battery so it has adequate clearance from the terminals. 3. Replace the two terminals on the battery leads (the positive and negative terminals are different sizes). New ones are available from any good car shop. 4. Connect the earth connection to the battery negative terminal. 5. Disconnect both dynamo leads and use a long length of wire to connect the small dynamo terminal to the battery positive for five to ten seconds. This removes any magnetic memory that the dynamo has so it charges the correct way. 6. Re-connect the dynamo. 7. Connect the positive lead to the battery. 8 Swap the 2 small wires on the coil over. These just pull off and slide back on. If in doubt you should end up with the black and white wire connected to the terminal marked - or neg. 9 If the red light on the dash goes out when the engine is running all is well. If not repeat sections five onwards. 10 If you have one of the very early cars with an ammeter you will need to reverse this as well or it will read backwards. Some of the very early cars have heaters that run in reverse as well but only the VERY early cars do this. The windscreen wiper motor also runs the opposite way but this has never proved a problem. Quote Link to comment Share on other sites More sharing options...
CaMpylobacter Posted November 4, 2009 Share Posted November 4, 2009 ^ yuh i changed the coil leads over on the ferguson i changed over (most recently). i'd trust where my advice came from more than mr forced Quote Link to comment Share on other sites More sharing options...
cletus Posted November 4, 2009 Share Posted November 4, 2009 So if a positive ground car bumped into a negative ground car, would there be dzzzztttd when the bumpers touched?? Quote Link to comment Share on other sites More sharing options...
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