Technical 2 vs 3 connector in front indicators?

[edave]

Hello! Excited new owner of a 1965 500D

As I'm checking out what's working well, and what could use some love, I've discovered that one of the front turn indicators is not functioning. Specifically, the parking light works but the turn indicator does not. I've done all the usual checks and traced it down to a broken contact inside the indicator itself. (You may be thinking "just clean the contacts first!" and as I was going to do that discovered the broken contact)

So now I need to get a replacement indicator, but I am having a lot of trouble finding a replacement indicator online that has 3 (barrel) connectors on the back to make use of a dual filament bulb. From the wiring diagram I glanced at, the connectors are for Parking | Ground | Turn wires. However, all of the indicators I can find online seem to only have two connectors. Is this because after-market indicators switched to grounding to the chassis using the trim screws and eliminated the ground wire connection, or that most of the indicators I can find are for the UK market where (as I understand it) they do not use a dual-filament bulb and only use the indicator for the turn signal.

Thanks in advance!

 

[the hobbler]

Hello! Excited new owner of a 1965 500D

As I'm checking out what's working well, and what could use some love, I've discovered that one of the front turn indicators is not functioning. Specifically, the parking light works but the turn indicator does not. I've done all the usual checks and traced it down to a broken contact inside the indicator itself. (You may be thinking "just clean the contacts first!" and as I was going to do that discovered the broken contact)

So now I need to get a replacement indicator, but I am having a lot of trouble finding a replacement indicator online that has 3 (barrel) connectors on the back to make use of a dual filament bulb. From the wiring diagram I glanced at, the connectors are for Parking | Ground | Turn wires. However, all of the indicators I can find online seem to only have two connectors. Is this because after-market indicators switched to grounding to the chassis using the trim screws and eliminated the ground wire connection, or that most of the indicators I can find are for the UK market where (as I understand it) they do not use a dual-filament bulb and only use the indicator for the turn signal.

Thanks in advance!

Although we only use the indicator lights as indicators, we still have to use a dual-filament bulb in them as they are built for the European market.

 

[fiat500]

Hello! Excited new owner of a 1965 500D

As I'm checking out what's working well, and what could use some love, I've discovered that one of the front turn indicators is not functioning. Specifically, the parking light works but the turn indicator does not. I've done all the usual checks and traced it down to a broken contact inside the indicator itself. (You may be thinking "just clean the contacts first!" and as I was going to do that discovered the broken contact)

So now I need to get a replacement indicator, but I am having a lot of trouble finding a replacement indicator online that has 3 (barrel) connectors on the back to make use of a dual filament bulb. From the wiring diagram I glanced at, the connectors are for Parking | Ground | Turn wires. However, all of the indicators I can find online seem to only have two connectors. Is this because after-market indicators switched to grounding to the chassis using the trim screws and eliminated the ground wire connection, or that most of the indicators I can find are for the UK market where (as I understand it) they do not use a dual-filament bulb and only use the indicator for the turn signal.

Thanks in advance!

Yes, in the UK versions of the 500 and in most other cars of the era, the front and rear indicators have single-filament lamps for the indicators; the front side-lamp or parking light is separately held in a small socket in the headlamp reflector.
The main headlights on the "F" and "L" at least, do have three prongs for spade connectors, and one of these is for the ground. But on all other light-bulbs fitted to the car, whether with two soldered terminals or a single, the ground is provide by a contact in the bulb-holder with the exterior of the metal structure of the bulb. I think that in most setups, there is a grounding wire, spade-connected to the light fitting to provide continuity with the chassis, but these are short leads to localised grounding points.

I'm not sure if you're needing a new light fitting with three prongs, or a lamp/bulb with the three contacts, but Axel Gerstl website has some images of the options which might help you.

 

[edave]

Thanks! This was super useful to understand.

A few notes for anyone else who stumbles upon this:
1) 500N/D lamps (with barrel connectors) came with three prongs. However, you can install a 2 prong (w/ barrels), the parking and signal filaments will still work. You just need to be sure to have a good grounding connection thru the mounting screws for the indicator body. Given the spacing for where the indicator mounting bolts go on the body, I opted to firmly rest the bottom mounting bolt on the body for a good grounding connection. At least in my Fiat, when it was restored and the body was re-painted there is not a good contact for a washer to act as ground to the body, and I don't want to try and remove some paint to make it a good contact.
2) I saw several photos of the barrel-connector indicators online where the plastic housing for the connectors has a clear molding for the center, ground connector. I guess the actual connector was eliminated to simplify/make them cheaper.
3) In my 500D, a previous owner had replaced the headlight assemblies, which now has spade connectors. As part of that, the ground prong of the headlight assembly was wired (in series) to the ground prong of the indicator light. With a new signal indicator that has no grounding connector, I simply put a spade connector on the existing wire and bolted it to the indicator mounting bolt.
4) An original, 3-wire indicator light can still somewhat function without the grounding prong connected, but it is much, much dimmer. That made for some fun work figuring out what was going on!