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Old 23rd Aug 2010, 10:35 pm   #13
neon indicator
Retired Dormant Member
 
Join Date: Jun 2010
Location: Co. Limerick, Ireland.
Posts: 1,183
Default Re: Old car radio - how to change polarity?

An alternator is AC. The diode pack is wired differently for +V or -V earth. REALLY Old alternators had external diode pack and separate regulator (which is different for + or -). Modern alternators have diodes (usually 6) and regulator built inside case. Also regulation is different on a Dynamo and Alternator.

You can't feasibly change the polarity on a Modern car (too much electronics and engine management) and even 15 year old 20 year old with mostly only relays has a modern "all in one" Regulator -rectifier - Alternator.

We are flogging a dead horse.

[OT] In late 1970s I fixed car electrics and motor bike timing electrics as well as repairing radios and TVs after school. Eventually I got a 200cc Scooter. Magneto Ignition and direct AC drive to lights and horn from coils on stator. Flywheel of crankshaft had magnets. No battery. manual adding of oil to petrol (Two Stroke).

Recently I was helping my son fix a S/H scooter he bought. broken exhaust stud needed drilled and tapped. It's got ONLY battery starter. No kick starter at all. Fuel injection. Auto lube oil injection to crankcase. Electronic CDI for spark. All microprocessor controlled including choke. Water cooled 50cc two stroke with varator continuously variable transmission. AKA "Twist and Go". I'd not want to convert that to +ve earth either.

Google OBD port and car WiFi hijack ...

Last edited by neon indicator; 23rd Aug 2010 at 10:45 pm.
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