Ignition switch question

Gotta love that wiring . . .
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spidernut
Posts: 1905
Joined: Wed Jan 25, 2006 12:20 am
Your car is a: 1979 Fiat Spider Automatic
Location: Lincoln, CA

Ignition switch question

Postby spidernut » Fri Apr 07, 2017 1:04 am

Help needed for EFI ignition switch (1981+)

I am looking for a schematic/explanation regarding the function of each of the ignition switch terminals on the 81 and newer Fiat Spider ignition switch. I've found schematics for older switches that are different, but none for the newer models. I am trying to bench test the switch operation and have found the following:

With no key installed
Continuity between:
50 – Red
30 – Brown
INT - Blue and Blank

With key installed
Continuity between:
16 – White, Both wires

Continuity between:
50 – Red
30 – Brown
INT - Blue and Blank

In run position
Continuity between:
15 – Pink
30/1 – Black

Continuity between:
16 – White, Both Wires

Continuity between:
50 – Red
30 – Brown
INT - Blue and Blank

In start position
Continuity is exactly the same as in the run position - I can find no difference between the start and run position. There should be difference since the starter should only be turning over when the key is in the start position. It seems the brown wire on terminal 30 should not have continuity with the other wires (red, blue and black) unless the key is in the start position.

Any knowledgeable help would be welcomed.

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John G.
1979 Spider (Owned since 2000)
1971 124 Sport Spider (Owned since 2017)
1977 Spider (Sold 2017)
1979 Spider (Disposed of in 2017)
1979 Spider (Sold 2015)
1980 Spider (Sold in 2013)
1981 Spider (Sold in 1985)
2017 Spider (Owned since 2019)

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aj81spider
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Your car is a: 1974 Fiat 124 Spider
Location: Chelmsford, MA

Re: Ignition switch question

Postby aj81spider » Fri Apr 07, 2017 8:03 am

Here's how mine was wired. I can email you a Powerpoint diagram I created when I put my ignition relays in if you PM me your email address.

30 (Brown wire) is a power input. It powers INT in both run and start position and it powers 50 in start position (not run).

30/1 (Black wire) is the other power input. It powers 15/54 in both run and start positions.

If you have continuity between 30 and 50 and INT with the key out you have a pretty hosed switch and your starter will be running with the car off.

If you have a pin 16 I think you have an earlier ignition switch. My '74 has that pin and it goes to the fuel pump. On the '74 switch 16 is driven from 30 in both the run and start positions. Otherwise the connections are the same.
A.J.

1974 Fiat 124 Spider
2006 Corvette
1981 Spider 2000 (sold 2013 - never should have sold that car)

spider2081
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Your car is a: 1981 Spider 2000
Location: Wallingford,CT
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Re: Ignition switch question

Postby spider2081 » Fri Apr 07, 2017 8:33 am

This link has the schematic for later ignition switches. Scroll to page 11
http://www.njfiats.org/images/stories/s ... manual.pdf
Pretty sure none of the terminals on the back of the switch should have continuity with the key out of the switch. Also the wires should be soldered onto the switch and there should be a 6 pin Nylon connector on the wire pigtail.

This link shows the inside parts of the a Sepia ignition switch. (second generation) The last generation have the "INT" terminals in the center of the switch. There are little pins inside the switch that can brake or fall out if the electrical portion of the switch is removed from the mechanical portion and the the switch is rotated. These pins are needed to move the internal contacts to the off position. If the switch you have is a Sepia switch then this is what I think happened. Figure 11 in this link shows the top of the pins. They are the two little white dots

http://www.njfiats.org/joomla/images/st ... epair.html
The last generation switches used a slightly different internals with a black pin.


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