A Simple guide to converting your Aircooled VW from Dynamo/ Generator to internally regulated Alternator
The first thing to note is depending on if you are on 6 volt or 12 volt electrical system will dictate the position of your regulator on your dynamo. On 6 volt systems you will find the regulator screwed to the top of the dynamo/ generator body itself, whereas 12 volt systems will be on the left hand side of the vehicle (on beetles under the rear passenger bench seat, on buses typically in the engine bay compartment). To convert the system you will need to in the case of a 12 volt system connect the main power wires together and the two small gauge signal wires together (simply put the two thick wires together and the two thin together.
Next you will need to check which of your wires is the one leading to the alternator charging bulb on the speedometer. This should join to the spade on top of the new alternator body.
The other wire can go directly to your battery via the starter motor or direct depending on year it makes no difference really as long as the alternator has a good thick wire connecting it to the '+' of the battery from the 10mm threaded nut on top of your alternator.
Note if you are doing a 6-12 volt conversion you will need an alternator conversion kit which you can find on the left of this page. Note this includes the alternator, a stand which will take the larger bodied 12v alternator, a 12v alternator belt, backing plates for the different spacings and a 12v alternator pulley to match.
Choosing your alternator 55 Amp or 70 Amp
Obviously in the main bigger is better, however a 55amp alternator will not load your engine quite as hard as the 70amp, it is minimal but worth noting. The 70amp is recommended for anyone running an air ride system for the significant load added by the compressors, and also a bigger battery is a must or a leisure battery equally. Also if you have a bus and are running several functional elements of your vehicle simultaneously the 70 amp is a great idea.
The alternator and generator wiring circuit works on a reverse live circuit. The bulb itself is live (taking a black '+' off the board on all aircooled VW's, so the circuit is Earthing through the alternator (so make sure your gearbox earth strap is in good order). If the bulb does not light on the dash the alternator will not charge, it requires at least a 4volt connection to switch the alternator on, again this will be signified by the bulb first coming on and then going off shortly after the engine is started.
Good luck and happy wiring people!!, feel free to post your questions below!!