Fiat 124 Spider Alternator Upgrade



There are two ways of upgrading the stock alternator: by fitting a more modern higher-output unit, or for the pre-1977 Spiders, by fitting an internally regulated alternator from a later model Spider.

The first option is an aftermarket 95 amp alternator that drops right in and also provides higher voltage, making the lights brighter and wipers faster!
It is available from Auto Ricambi:

95 Amp Alternator

Here is a video of my friend's 124 Coupe's wipers after the fitment of this alternator, notice how much faster they are than standard Fiat wipers:

Fast Wipers

The price is comparable to a rebuilt stock unit from the well-known US Fiat Spider parts vendors.

Prior to 1977 Fiat Spiders came with an externally regulated 45 amp (some '75-early77s had 55 amp) alternator. It is possible to convert to the later style internally regulated unit, for simplicity and higher amperage (55 or 65amps).
The internally regulated alternators can be Marelli (55amps) or Bosch (55 or 65 amps, the alternator should have a label stating the part number and amperage). I have only converted Spiders using Bosch alternators, however the Marelli internally regulated one is wired the same way. I would go for the Bosch 65 amp unit, which came on some 1980 model Spiders and just about all 1981 and later Spiders.
All 124/2000 alternators are interchangeable size-wise, regardless if they were originally mounted on the left or right side of the engine, so the later type alternator easily bolts on the early cars.
The externally regulated alternator has 3 wires going to it:
-the 'power' wire, usually 3 black wires secured to a 6mm stud on the back of the alternator
-a wire going to the voltage regulator, gray, has female end
-a wire going to the charge light relay, yellow or yellow-red, has female end

The later unit has only two connections:
-one for the 'power' wire, a 6mm stud on the back of the alternator
-a male terminal for the wire going to the charge light

The later type alternator should bolt into place on the right hand side of the engine.
With the battery disconnected connect the black 'power' wires to the stud on the back of the alternator, connect the yellow (or yellow/red) wire to the male terminal, and leave the gray wire disconnected.

There is one more thing to do, as the two alternators use different methods for turning on the charge light.
The earlier type alternator gives a +12V signal to a relay when the alternator light is supposed to be on, and the relay switches a ground signal to the light. The later type alternators switch ground directly to the alternator light, so the relay is not needed.
This relay is located on the left (driver's) side inner fender in the engine compartment.
To make the light work properly, disconnect wires 85 (yellow or yellow/red) and 30 (violet/white) at the relay, and connect them together. The other two wires going to the relay are both ground wires, and can be left connected, or you can remove the relay and cut the ground wires off at the harness.
Start up the car, and measure alternator output voltage at the back end of the alternator.
It should be at least 13.5 volts. The engine may have to be above idle to achieve this.

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