Ignition Switch Color Harness - help a colorblind brother out!

[18Fiatsandcounting]

I have bench tested and serviced around 10 Sepia ignition switches that have a terminal 16, most do not. Terminal 16 connected to terminal 30 in the "start" position only on all the switches I tested.

That is consistent with the original Sipea ignition switches in both my '69 and '71, that is, terminal 16 is connected to power (through the brown wire to the starter) only when the switch is in the start position. In my two cars, though, terminal 16 is unused as they both have mechanical fuel pumps.

So, my understanding is that the electric fuel pump gets power through terminal 16 when you're trying to start the car, and it gets power from the fuel pump relay (if it has one) when you release the key to the "run" position. This makes sense, as there may not be much oil pressure yet when you're trying to start the car, but you do want the fuel pump to operate in the event the car hasn't been started in a long time and the float bowl is dry. Once the car is started, the relay takes over, and if there is a loss of oil pressure, the fuel pump shuts off for safety reasons. Like in an accident where you wouldn't want the fuel pump to continue running.

-Bryan

[spider2081]

Bryan that is what i think also. I didn't quote your post but believe your explanation is what Fiat's intentions were and how the circuit should work.
I think the early Sipea ignitions switches were constructed different from the later years. The early ones have a "C" clip in the center of the terminals, Later switches have the "int" terminals in the center.

[18Fiatsandcounting]

I think the early Sipea ignitions switches were constructed different from the later years. The early ones have a "C" clip in the center of the terminals, Later switches have the "int" terminals in the center.

Yes, I think we're on the same page. For what it's worth, here's how the back of my Sipea switch looks (looking at it from the rear), oriented so that Terminal 30 (brown wire) is at the 1 o'clock position:

1 o'clock: Terminal 30. Brown wire to starter.
2:30 o'clock: First INT terminal. Connects to various accessories. Active +12V except in "OFF" switch position.
3:30 o'clock: Second INT terminal. Same connection as above.
5 o'clock: Terminal 50. Red wire to starter solenoid. Connected to Terminal 30 above when key in "START" position.
7 o'clock: Terminal 30/1. Connects to + output on alternator.
8:30 o'clock: First Terminal 16. Unused on my car.
9:30 o'clock: Second Terminal 16. Same connection as above.
11 o'clock: Terminal 15. Blue/black wire to ignition system and large pink wire to fuse box. Connected to terminal 30/1 when in "START" or "RUN" positions.

-Bryan

[18Fiatsandcounting]

Stuart, see if this post helps:
https://fiatspider.com/f15/viewtopic.php?t=37135

-Bryan

[stuartrubin]

I ended up using the original switch. I am fairly certain that the problem was actually one of the wire harnesses. It was visibly "burned out" looking, the plastic shrowd around the quick-connector was blackened and partly broken, etc. So, I just snipped it and put a new connector on. I still needed everyone's help for putting it back together, so thank you!

For future readers, here are the ignition switch connections I made on my '75 with the original Sipea switch.

Wire(s) --> Switch Contact #
Black --> #30/1
Brown --> #30
Red --> #50
Pink, Blue/Black stripe--> #15
Blue, Blue/Red stripe --> INT
Gray, Green/Black stripe --> 16

Feel free to correct me if this does not look right. Thanks again.

[18Fiatsandcounting]

Stuart, that looks right to me. And good on you for keeping the original switch. Many people just replace it, when the issue is actually bad connections either at the switch or somewhere down the line. The original Sipea switches in my two spiders have been through Hades and back again (in terms of endless starter motor cranking, lights left on all night, shorts, 200K miles, etc) and they are still fine. Take out the electrical portion, polish the electrical pads with some 600 grit emery paper, put it back together, quaff a beer or two, and enjoy for another 10 or 20 years. Ahhhh...

-Bryan

[spider2081]

Feel free to correct me if this does not look right.

I also believe this is correct Stuart.
Great to see your issue is resolved.

I am one who believes the original Sepia switches, both mechanically and electrically, are a much higher quality product that the available aftermarket switch assemblies. I believe in keeping them over replacing them. I mentioned earlier the female terminals on the cars wires loosen in time and need to be addressed. Replacing them is best but because of the different wire sizes used in different model years it is not a one size fits all. Some cars have a #8 brown wire, finding the correct terminal for this size wire is not easy. The other wires can range in size from #10 to #16 so different size terminals are required for them.
I don't think removing the electrical section from your ignition switch assembly will give you access to the switch contacts. The switch contacts are accessible in early Spider's Sepia switches but somewhere around 1972-74 the electrical sections were made different and to access the contacts, 3 tiny roll rivets have to be drilled out to access the contacts. Reassembling then becomes a challenge.

Spiders that were delivered with an automatic transmission used a Bosch cube relay between the ignition switch and the starter solenoid. Referencing that wire diagram I would consider modifying the "start" circuit to one with a relay eliminating the solenoid current from the ignition switch.

[aj81spider]

Yes this is true.
I don't think Fiat and/or other publishers of Fiat Manuals are all in agreement and with out errors. I have never owned or a carbureted Fiat. I am looking at wire diagrams from Mirafiori.com and Clymer's shop manual for 1974, 1975 and 1976 Spiders. Both of these diagrams have an electric fuel pump. Both diagrams show 2 power sources for the pump. One directly from terminal 16 of the ignition switch (green/black wire} and the other from a relay. The relay in the Clymer diagram item # 128/3 identified as "fuel pump and ignition mode relay control switch" The wire diagram I downloaded has the relay identified as " Fuel pump relay"
As stated the diagrams are difficult to see/read.
Like all auto manufacturer's Fiat made mid year changes and I believe the publications probably illustrate either before the change or after the change but seldom both.
A number of Spiders with dual points have been modified to one set of points or electronic ignition. This could eliminated the ignition mode relay. and eliminate the safety aspect of the oil pressure being required for the fuel pump to run.

I have bench tested and serviced around 10 Sepia ignition switches that have a terminal 16, most do not. Terminal 16 connected to terminal 30 in the "start" position only on all the switches I tested.

So I spent quite a bit of time looking at the wiring diagrams and then looking at my car. Unfortunately I don't have the original ignition switch so I can't tell you whether it was active in Run and Start or just start. However after quite a bit of study I think you are right and I am wrong (and my car appears to have the ignition relay removed, and my fuel pump therefore runs with the engine off).

[18Fiatsandcounting]

For what it's worth, the "most accurate" wiring diagram that I have found is the one in the owner's manual for that specific model year. Yes, these can be difficult to find since they tend to get lost over the years. But, some of the Fiat vendors sell reproduction manuals for some model years, which is how I got them for my '69 and '71 spiders. So far, I haven't found any mistakes in the wiring diagrams.

-Bryan