Dim right turn signal

[essenz]

Do some final testing on a newly purchased 84 Pininfarina before I take it to get inspected.

So far the only issue I have is a "dim" right turn signal. Here is an overview of what I've checked and additional details.

1. Front R and L work/click fine
2. Rear L clicks and flashes with full brightness,
3. Rear R clicks and flashes but is noticeable dimmer, like half of bright.
4. All other lights are good. Backup lights nice and bright, brake good on both sides, etc.,
5. Turn signal bulb is 1156, tried swapping, also tested on the bench with 12v

What I tried...

Cleaned all the connection terminals - no change.
Attached a volt meter to the dim L signal, when it flashes, according to my meter the voltage spikes from 3V to ~8.5V.

My assumption is the bulb is dim because its not getting full voltage. Not sure where to go next here... Maybe the relay that controls the flasher? I wasnt sure if the same relay controls both front and rear, if it did - then why would the front be acting fine.

It will "probably" pass inspection like this, but who knows. Would be nice to fix.

[spider2081]

It could be the turn signal light bulb socket is not making a good contact to the printed circuit board. Have you tried using a test light at the connector for the right sides light assembly. I think its the first pin from the center of the trunk. Remove the light board from the light assembly and using the sharp point of the test light scratch the area below the first pin in the connector. The test light should flash with the turn signal. Both should be dim. Remove the Turn signal bulb from its socket and the test light should flash full bright. If it does the issue is most likely the turn signal sockets connections to the printed circuit board. If it does not flash full bright the issue could be in the driver side printed circuit board or the connecting harness.

[essenz]

Made a little bit of progress.

I noticed alot of the bulbs were 1156. Factory is 1063 (which they dont make), but they do make an 1073. 1073 draws about 21W vs the 26W of the 1156. So my working theory is all these 1156 bulbs are pulling too much amps, and since the rear R turn signal is the last in line, there isn't enough power for it. So I swapped all the 1156s for 1073. I also changed the side marker lights to LED, so less watts again - but since they dont flash - the LED shouldn't be a big deal.

This helped alot. The rear R turn signal is alot brighter.

I noticed the front turn signals use 1157, not sure if there is a lower watt equivalent to use up front. I could do LED, but will need to uograde the flasher/relay to support LED right, otherwise I might lose the clicking sound?

[spider2081]

So my working theory is all these 1156 bulbs are pulling too much amps,

Keep in mind that only 2 bulbs are lit at a time when the turn signal is used. The green light in the dash is lit by the flasher when the turn signal bulbs are between flashes.
I think most a 2L Spiders use 1156 bulbs in their tail light assemblies.
A dim bulb is most always traced to a poor connection ( high resistance) causing an unwanted voltage drop and reduced current flow in the circuit. The tail lights in your car have a history of poor connections between the light sockets and the printed circuit boards. The connection is made with a simple hollow rivet (sometimes called an eyelet) they are not soldered to the board.
Changing bulbs to a lower current bulb is working around the problem not repairing the problem.
One way of testing the connections is to place one volt meter on the copper printed circuit and the other meter lead on light socket metal that connects to the printed circuit. The voltmeter should read 0 when the bulb is lit. That is because a good connection has nearly zero resistance. There are 3 connection points for each socket. The light bulbs center contact has one connecting point. The light bulbs outer connection has 2 connecting points.

[SpiderGuy]

So my working theory is all these 1156 bulbs are pulling too much amps,

The tail lights in your car have a history of poor connections between the light sockets and the printed circuit boards. The connection is made with a simple hollow rivet (sometimes called an eyelet) they are not soldered to the board.

There are 3 connection points for each socket. The light bulbs center contact has one connecting point. The light bulbs outer connection has 2 connecting points.

I agree, the connections are weak points and 40 years of oxide corrosion can further corrode the connections. When I tested mine I found Zero continuity between the Circuit Boards and the Light Fixtures.
I fixed mine by Soldering all the Board Circuits to all the Bulb Fixtures. I also Made sure to clean the corrosion off of the Springy Center Post contacts. SUCCESS Got em all shining BRIGHT