Wiring Up The Bosch Gear Reduction Starter

[RRoller123]

Wiring up the new Bosch gear reduction starter on Tim's 83.

There are 2 large studs and 3 Faston connections on this starter, not sure what goes where, nothing is labeled! My AR gear reduction Starter just has 1 Faston and 1 Stud.

Anyone know how this Bosch gar reduction starter is supposed to wire up? I think the light red that normally pulls in the solenoid is attached to the isolated Faston, and the more accessible Stud gets the power connections, but his wiring diagram also shows 2 brown and 1 black wire om the '83.

We are putting the starter in and will wire it up later when we get this info.

Thanks for any help, as always,

Pete

[tima01864]

It is not a gear reduction starter, This is a rebuilt starter from an 83, There were changes in the 83-85 years, Called a short body starter.

There is one fast on connection on the left engine side and two on the fender side, Are the two for accesories, for an Automatic? Any one know?

[RRoller123]

oops, my mistake.

[tima01864]

I would just like someone to answer

[RRoller123]

I don't think anyone knows, but here is what I suggest.

That lone Faston at the left is probably the pull in connection for the solenoid. We can test that by applying 12VDC and seeing if it it does that.

The bottom post is directly wired to the windings, isolated from the top post when idle, as we checked with a DVM. I bet the top post connects to the bottom when that left Faston is powered. We can check that too.

Those other Fastons to the right? They remain a mystery to me anyway.

[18Fiatsandcounting]

Sorry guys, I haven't answered because my Fiat knowledge only extends up to 1980 or so. What I can tell you is that the large post in the top of your picture is for the large cable that goes to the battery. However, earlier Fiat starters just had one Faston connector lug, and that was for the red wire that went to the ignition switch. If you apply 12 volts to that red wire (when you turn the switch to "start"), the solenoid engages, pulls the contact closed between the two large posts, and current then flows to your starter motor.

In your case, one of those Faston connectors is the above function, but I don't know which one, and what the other two connectors do. I imagine some sleuth work with a DVM could figure it out, as you've suggested.

-Bryan

[tima01864]

Any ideas as to what the tabs on the right are for?

[18Fiatsandcounting]

Any ideas as to what the tabs on the right are for?

Unfortunately, no, at least not with any amount of expertise. Maybe a switch that closes when the starter solenoid is engaged and thus the engine is cranking? Perhaps for a sensor that tells the onboard computer to adjust the spark or the fuel delivery or emissions controls when the engine is cranking, and then when the solenoid disengages, the switch opens up and the spark/fuel go back to normal (running) operating parameters? Just a wild and possibly crazy guess.

My question for you is: Does your car have the wires that connect to these? If so, can you find these colored wires anywhere on a wiring diagram?

-Bryan

[tima01864]

Nothing on the wiring diagram, Points to those connections. Maybe just there for another model, Missing on the starter is identification of the terminal. Ah well, trial by error here. Thanks for the input Bryan

[spider2081]

I tried to respond 2 previous times and bot times an error msg came up when I hit submit so they say 3 is a charm:

Often one end of the solenoids coil is internally grounded to its cse so only battery voltage is need on the other side to engage the solenoid. You could use an ohm meter on its lowest scales and check each of the 3 terminals to the solenoids case. If one of them measures less than 5 ohms but not 0 ohms that is probably the terminal the wire from the ignition switch "start" wire would connect to.
The 2 terminals on the right in the photo look like they might be visibly and physically connected together. Is that the case?
As previously stated when the solenoid is energized some solenoids have a terminal that outputs battery voltage. This terminal is used to bypass the ballast resistor in cars using ignition points. In later cars it can be used to tell the fuel computer the car is in the "start" mode. As far as I know no Spiders Fiat or Pinna used these solenoid features.
Lastly some solenoids have both of the solenoids coil terminals available externally. the ground is then supplied by the automatic transmission "park" switch or the standard transmission's clutch switch.

The solenoid photo looks like it could be a Bosch BO157-SLO2 solenoid used on some BMWs
Hope this helps I tried to post this yesterday and again this morning

[tima01864]

Thanks for shedding light on this mystery 2081 and your persistence

[18Fiatsandcounting]

This is more background information than a solution for your issue: On my '69 Chevy truck (yes, 1969), the starter motor and ignition coil is set up so that the coil receives a full 12 volts when the engine is cranking, and then once the starter is no longer cranking, the coil voltage supply goes down to 6 or 8 volts or so. The idea was to provide a hotter spark during starting, but then once the engine was running, to back off on the coil voltage so as to lengthen the lifetime of the points and the coil.

But seriously, this CAN'T be what is going on in your early 80s Fiat... Or can it?

-Bryan

[RRoller123]

The 2 Fastons to the right are electrically connected to the bottom stud.

[spider2081]

I'm still having trouble with posting in this chat room. I tried replying this moring but the error came up again.

I think 1978 was the last production year Fiat used ignition points in the Spiders distributors.
I don't think Pininfarina offered automatic transmissions as an option. Fiat's automatic transmission "park" circuit used a relay to complete the connection between the ignition switch and the solenoid "start" terminal. The Transmissions "Park" switch supplied a ground to the relays coil not to the solenoids coil.

The Bosch starter may be the correct starter for the 83-85 Spider but I don't think the solenoid in the photo would have been. I think there is only one red wire with a spade connector coming from the ignition switch terminal 50. On the top stud of the solenoid usually there are 3 ring terminals, the big battery cable, the wire connecting to the alternators output post, and the brown wire to the ignition switch terminal 30. The bottom stud has only the starter motors conductor on it.
I think the correct terminal (of the 3) to use can can be confirmed with an ohm meter but for sure it would not be the 2 that are connected to the bottom stud.

[tima01864]

One of the fastons to the right in the photo. Trial and error