Converting the Volvo Amazon or 1800 from dynamo to alternator

There seems to be a degree of confusion over exactly what is involved in converting a Volvo Amazon or 1800 from dynamo to alternator from the electrical point of view.

There need not be, because it is very simple. The wiring for either unit is almost the same. Shorn of all unessentials, the wiring diagram is given here:

Wiring diagram of charging circuit for Volvos equipped either
with a dynamo or with an alternator with separate regulator

The "Generating Device" is either a dynamo or an alternator. The "Regulator" is the appropriate regulator for whichever type of "Generating Device" is fitted. The earth connections to the D- terminals may be either explicit wires or connections made by virtue of the item being bolted to grounded metal.

The only difference is that the B+ terminal is on the regulator for a dynamo system and on the alternator for an alternator system.

It may readily be seen that the conversion is simply a matter of taking the dynamo and dynamo regulator off, bolting the alternator and alternator regulator on, and connecting the existing wiring to the appropriate terminals.

Note that with more recent alternators, the regulator is built in to the alternator itself. In this case it is even simpler: simply ignore the "Regulator" part of the diagram and all the wires between the Regulator and the Generating Device, and connect the wires that originally went from the regulator to the rest of the car to the appropriate terminals on the alternator. The DF connection can be ignored, since it is internal to the alternator, and there may or may not even be a terminal for it.

Do not try and use an existing external regulator with a replacement alternator that has its regulator built in. This will result in what is technically known as "undefined behaviour", which is to say that it will happily come up with its own definition which is highly likely to include undesirable outputs in the form of smoke. Instead, remove the existing external regulator entirely and follow the preceding paragraph.

The wires connected to the B+ terminal on the regulator on a dynamo system may seem to have "nowhere to go" on an alternator system. This is not the case. They should be connected together, the connection isolated from the bodywork etc. and a wire run from the connection to the B+ terminal on the alternator.

Do not be confused by the apparent greater complexity of the wiring diagrams in the Volvo workshop manual or other such sources. They're just confusing because they have a lot of extra information which is not relevant to the job in progress and because of the way they are drawn. The above diagram strips out all the redundant information and is drawn as simply as possible.

I make no comment on the debate over whether the alternator should be installed in the same position as the dynamo (manifold side) or in the position in which Volvo installed alternators on four-cylinder models (distributor side), other than to note that installing it in the same position as the dynamo avoids any need for extending the existing wiring to reach the other side of the engine and is therefore simpler.

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