Technical Wiring running through firewall

[Mikeb3311]

Hi all!
Recently acquired a 1980 FI 124 spider. There is a wire that is chewed through that appears to pass through a hole in the firewall. This wire seems to have gone directly over some of the spark plugs even though it is obviously not a plug wire. I have looked through the online wiring diagrams but have not been able to find it. I cannot see somewhere the wire might have terminated at. It looks to have had a green covering. I will probably end up investing in an owners manual just for the complete wiring diagram, however I would like to not do that if possible. Even though it looks like I will have to tear up the interior to replace it anyways, some help diagnosing it would be beyond appreciated. A photo is attached. That little stringy wire is all thats left.... Hopefully that can provide some context to where it is. I am sorry the photo is not very clear... Thank you so much in advance.

 

[124BC1]

There is a colorized wiring diagram available for a 124 Spider (older model than yours, but mostly the same) in the Downloads section at the top of this page, try this link:-

https://www.fiatforum.com/downloads/1969-fiat-124-sport-spider-colorized-wiring-diagram.376/download

As regards the mystery green? wire... There are 2 wires that run across the valley between the cam boxes and beside the spark plugs on the 124TC engine.
These 2 wires go to 2 sender units, the green wire goes to the rearmost sender for the water (engine coolant) temperature gauge, the other wire which can be either green or green with a black tracer goes to the forward sender unit which, in the event of excessively high water temperature, sends the needle in the water temp. gauge to maximum (iirc, it may also illuminate a high temp. warning light on cars so equipped).

These 2 wires run from the cyl. head temp. sender units to the wiring loom hidden behind a metal shield running along the width of the engine bulkhead and then into the passenger compartment and onwards to the rear of the instrument panel/water temp. gauge. Neither of these 2 wires are live, the rearmost one makes the gauge operate by inserting a variable resistance into the ground circuit of the gauge to give a temp. reading, the forward one make the gauge read maximum (+/- a coolant temp. warning light) by acting as a ground for the temp. gauge.

Hth

 

[Mikeb3311]

There is a colorized wiring diagram available for a 124 Spider (older model than yours, but mostly the same) in the Downloads section at the top of this page, try this link:-

https://www.fiatforum.com/downloads/1969-fiat-124-sport-spider-colorized-wiring-diagram.376/download

As regards the mystery green? wire... There are 2 wires that run across the valley between the cam boxes and beside the spark plugs on the 124TC engine.
These 2 wires go to 2 sender units, the green wire goes to the rearmost sender for the water (engine coolant) temperature gauge, the other wire which can be either green or green with a black tracer goes to the forward sender unit which, in the event of excessively high water temperature, sends the needle in the water temp. gauge to maximum (iirc, it may also illuminate a high temp. warning light on cars so equipped).

These 2 wires run from the cyl. head temp. sender units to the wiring loom hidden behind a metal shield running along the width of the engine bulkhead and then into the passenger compartment and onwards to the rear of the instrument panel/water temp. gauge. Neither of these 2 wires are live, the rearmost one makes the gauge operate by inserting a variable resistance into the ground circuit of the gauge to give a temp. reading, the forward one make the gauge read maximum (+/- a coolant temp. warning light) by acting as a ground for the temp. gauge.

Hth

Thank you so much! This has been incredibly helpful! Now I just have to complete the possibly nightmarish task of changing out those wires lol..