Ignition SW to coli wire Q.

[2002phil]

I'm close to getting my car running after the engine rebuild. I have a ignition SW issue that has me scratching my head.

When I turn the key to the run position, I get 12v at the +B side of the coil, all good. Turn the key to engage the starter.
Car turns over and fires, I release the key back to run and I lose the 12v at the coil. Turn the key off then back to run and I get
the 12v back at the coil. Wiring diagram only shows a single path from the sw to the coil. Am I missing something or maybe I have a bad
ignition SW ?

any ideas?

Thanks
Phil

[18Fiatsandcounting]

Phil, it does sound like you have a bad ignition switch. The +12V to the coil should be present in both the "run" and "start" positions of the switch, and it is very common for one or the other to behave intermittently. Usually it's the "run" position that starts misbehaving.

The switches can sometimes be taken apart and fixed, although many folks just get a new switch. Each has its pluses and minuses: Fixing the switch it not always possible and sometimes only lasts for a few years, and a new switch (usually not exactly the same terminals as original) often has to be wired up differently.

-Bryan

[2002phil]

Hi Bryan,
After read various post about the ignition SW I think you've confirming what I suspected. I'll take a closer look at it.

Regards
Phil

[18Fiatsandcounting]

Let us know what you find out. Sometimes it's as simple as a loose connection on the rear of the ignition switch, and sometimes you can take apart the electrical part of the switch and clean the contacts. I don't know what design of switch you have, but on earlier spiders (like mine), the "run" part of the switch stops working because the plastic cam lobe that moves the contacts slowly "melts" with the heat through this contact, then starts to act intermittently, then stops working altogether.

-Bryan

[spider2081]

Phil
The original ignition switch would have been manufactured by Sipea. That name would be stamped in the shinny cover where the key is inserted into the switch. If the switch in your car has symbols on the shinny face that resemble Roman Numerals it might be an after market switch and may not be wired properly.

[2002phil]

It is an aftermarket switch.

[2002phil]

Hey Bryan, turns out it was the small plastic piece that you described. It had melted just enough to be a problem. missed it the first time i looked. I was able to tweak it a bit to make it work again. Now the car starts and runs. I will replace the switch soon but now I need to finish putting the car back together so I can drive it for the first time.

Phil

[18Fiatsandcounting]

It had melted just enough to be a problem.

Awesome, Phil, sounds like progress! I had several switches where the plastic cam lobe softened and flattened, but I took a soldering iron (15 or 25 watts or so) and used the hot tip to carefully reshape the lobe. Not perfect, but it worked well enough that the contacts opened and closed again. It only worked in some cases, as some were too far gone to repair.

If anyone knows a source for those plastic cams, or is handy enough with a 3-D printer to make them, many ignition switches could be saved.

-Bryan

[spider2081]

great you are back on the road.
I think Fiat changed from an ignition switch with push terminals on the back of the switch to wires soldered to the switch terminals and and a pigtail with 6 cavity connector around 1977. My guess is the change was an attempt to reduce the operating heat at the terminals.

[tima01864]

So the soldered terminals are from the factory. I was wondering about this.

[spider2081]

So the soldered terminals are from the factory

Yes and the composite the terminals are in is a black bakelite like material. It has a higher melting temperature than the Nylon like material used in the Lada switches. So soldering the wires to the terminals does not melt the material.