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Discussion Starter #1
Hello -- planning for the winter projects and one item was to replace the ignition switch. For a 91/S4 it seems like vendors are selling either 3-wire or 4-wire versions (in fact mrfiat sells both versions as suitable for a 91). Looking at the service manual from back in the day, it looks like it should be a 4-wire. Just wondering if anyone had replaced theirs and would know. If not, I'll just hold off ordering until I pull the old one out -- which according to previous alfabb posts will either be a piece of cake or a nightmare.....

Thank you
 

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The one I just removed from a 91 Spider is 3 wire plus 2 small wires( maybe a warning buzzer).
Jon
 
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I concur Jon, 2 small wires (20-22ga.) are for the "key in ignition" buzzer mounted to column shaft.
 
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While you are in the planning stage, here is the hex head screw to use when installing the new ignition switch.

You do not want to use the break away safety screw that comes with the new one. Once you remove the original, you will not want to do that again.

IMG_1039.jpeg
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Good luck,

Vin
 
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Discussion Starter #5
Thanks for the responses. I did hear back from mrfiat and they essentially said that the original switch could be either 3- or 4- wire -- a factoid I am having some problems wrapping my brain around. But I guess Alfa was known to make changes mid-year.

Also, thanks for the tip on replacing the security screw in case I need to revisit the switch in the future.
 

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The original ignition switch from my 1988 Spider has a plug with three heavy gauge wires (Red, Brown and Black):
1651746

and a two-terminal plug with lighter gauge wires (Red and Black) for activating the "key in ignition" warning buzzer:
1651747

The replacement switch I purchased came with four heavy gauge wires. Three of them (Red, Brown and Green) were in a plug together and the fourth one (Black) was in a separate, single terminal housing:
1651748

This "4-wire" switch also had a pair of lighter gauge wires (to feed the "key in ignition" buzzer), but both of those smaller wires were black.

To determine how to use the 4-wire switch with my existing wiring, I did a bit of research. What I discovered is that the Green wire was used to bypass the ballast resistor on the coils of Pre-'82 cars during cranking. The external ballast resistor was eliminated on breakerless ignition (L-Jet) cars, since it was built into the coil, so there was no longer a need to have a resistor bypass circuit, and the Green wire became redundant. But in order to suit a wider range of model years, the switch manufacturers left the Green wire and merely added a separate Black one.

On my L-Jet Spider, the wiring harness plug needed to connect with the Red, Brown and Black wires fron the ignition switch. In order to satisfy that on the replacement switch, I simply released the Green and Black terminals from their respective plug housings, reversed and re-placed them. The result was a wire color combination in the three terminal plug (Red, Brown and Black) that matched the original, with the Green wire separate, not getting used or re-connected to anything.
 
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