82 Spider Speedometer Wiring

[FiatMac]

I just swapped out my 80 mph speedometer for one of the 140mph ones from an older Spider. There are two wires on the original 80mph speedometer that are not on the 140mph speedometer--The ones that show as Red (actually red/yellow)and Black on the photo below. The black wire is connected to the ground side of one of the lamp holders. The red/yellow wire runs into the wiring loom with no disconnect. I had to cut the wire to remove the speedometer.

I cannot find these wires on any wiring diagram. I just abandoned the wire with the 140 install. There appear to be no ill effects, but I am curious as to the purpose. I am surmising that it is a signal wire for some service alert function (possibly the O2 sensor?) that trips off of odometer miles.

Anybody know?

[JammerX19]

I will have the same question myself when I go to install mine.

[Europa]

What year Spider is the 140mph speedometer from?

[fiat218]

What year Spider is the 140mph speedometer from?

74 or no, I thought they all just plugged in

[GeorgeT]

I suspect it is to send a signal to the box that turns on the lamp that tells you to replace the O2 sensor every 30,000 miles.

[FiatMac]

I suspect it is to send a signal to the box that turns on the lamp that tells you to replace the O2 sensor every 30,000 miles.

That is what I suspected as stated in my post. Just looking for confirmation since I can't find a wiring diagram that shows it.

Further information is that I have only seen it on fuel injected cars. I went and looked at speedometers from my fuel injected '80 and '83 parts cars and they both have these wires, although on the '83 the color is different and it is wired into the connector. I checked on my '76 and '78 cars, and they are both 140mph and identical to the one that I just installed in my '82.

[GeorgeT]

Find Brad Artigue's wiring pdf for '81-'82 Spiders and go to Diagram H. Just to the right, in the middle is the speedometer icon showing a Red/Green wire going to the box.

[bradartigue]

I just swapped out my 80 mph speedometer for one of the 140mph ones from an older Spider. There are two wires on the original 80mph speedometer that are not on the 140mph speedometer--The ones that show as Red (actually red/yellow)and Black on the photo below. The black wire is connected to the ground side of one of the lamp holders. The red/yellow wire runs into the wiring loom with no disconnect. I had to cut the wire to remove the speedometer.

I cannot find these wires on any wiring diagram. I just abandoned the wire with the 140 install. There appear to be no ill effects, but I am curious as to the purpose. I am surmising that it is a signal wire for some service alert function (possibly the O2 sensor?) that trips off of odometer miles.

Anybody know?

Oxygen Sensor reminder lamp. If you trace it far enough you'll find the thing itself

[FiatMac]

Thanks!