The car I just bought has recently had a new battery, alternator and starter.
I was told that the battery voltage reversed and damaged these components, it also seems to have blown any fuses to the stereo and taken out the stereo head unit.
Has anyone heard of reversing batteries before? I haven't!
Thanks
Mark
Battery voltage?
Moderator: RichardW
What they may have meant is the Battery was connected in reverse, effectively making the car positive earth. It would have meant most of the voltage critical items would have had current running through them in reverse. Most earthing circuits within components have diodes to prevent the reverse flow of current/voltage through them during normal operation. Connecting the battery in reverse would have simply blown them, because they weren't designed to run that way. Have you ever seen the warnings on car stereo equipment saying, Negative Earth only, well thats what most modern cars are, I don't know of any Positive earth vehicles currently in production, Dave Burns??
Gareth
Gareth
The story the previous owner was told is that the battery had spontaneously reversed voltage!
I must have a nasty suspicous mind cos I can't help thinking that the garage changed the battery, fitted it backwards, blowing the starter and alternator, and then made up this ****ocks to cover their mistake!
Mark
I must have a nasty suspicous mind cos I can't help thinking that the garage changed the battery, fitted it backwards, blowing the starter and alternator, and then made up this ****ocks to cover their mistake!
Mark
Lead - Acid batteries CANNOT reverse polarity, its is a physical and chemical impossibility, so some one has ****ed up the battery connections!
BUT, as Dave said, that's not going to solve your problems!
Check that you don't have any other system failures in the car due to this mistake: the obvious systems at risk are the engine management system, ABS computer, A/C computer etc. If all these work, you can count yourself lucky.
The voltage regulator on the alternator MAY have been damaged by reverse polarity, but I can't see the starter getting damaged unless they tried to use it (since it's a D.C. device IT can have reversed polarity under these conditions!)
The radio may be sevicable - try getting a reputable radio supplier to look at it.
//NiSk
BUT, as Dave said, that's not going to solve your problems!
Check that you don't have any other system failures in the car due to this mistake: the obvious systems at risk are the engine management system, ABS computer, A/C computer etc. If all these work, you can count yourself lucky.
The voltage regulator on the alternator MAY have been damaged by reverse polarity, but I can't see the starter getting damaged unless they tried to use it (since it's a D.C. device IT can have reversed polarity under these conditions!)
The radio may be sevicable - try getting a reputable radio supplier to look at it.
//NiSk
>> "Lead - Acid batteries CANNOT reverse polarity"
technically speaking, yes. However, in cases we might be better talking about "Lead sulphate - Acid" batteries, and the chemistry is different. Polarity reversal can occur. Given that, if the car was in regular use and the battery maintained, reversed connection seems more likely.
technically speaking, yes. However, in cases we might be better talking about "Lead sulphate - Acid" batteries, and the chemistry is different. Polarity reversal can occur. Given that, if the car was in regular use and the battery maintained, reversed connection seems more likely.