Turn signal issue
 

I have an '87 coupe. For some reason when I turn on the left turn signal on it starts flashing very fast like the light bulb is out. The right signal has normal speed. I checked the fuse - it's fine. Checked the bulbs front and rear - all intact and work fine. If I use the hazard button it has a normal speed so this is isolated to left side only. My next guess is it's the relay but could I be missing something?

I worked on a 914 recently that flashed quickly on both sides so I changed the flasher. Then the left side and 4-ways worked fine and the right side signal flashed quickly. I replaced the bulbs and that fixed it. When bulbs flash quickly, you can't tell if they are as bright as the ones that flash normal...it looks dimmer but you think it's because they are flashing quickly. I usually always replace the bulbs with a lighting problem because after years of use the contacts wear quite a lot.

You do not mention how the tach directional signal lights are working. They are also a part of the flasher/directional circuit. Try swapping the front and back left and right side directional bulbs to see if the fault moves.

In my 1980 Porsche used a 4 post flasher that provided an internal connection to ground threw a small transistor circuit for the tach directional lights. Sometimes the flasher circuit would cause fast flashing or a constant dim tach directional light or a combination of both. In the 1985 model year Porsche changed the design to a three post relay and tied the two tach directional lights directly to ground.

Likely the flasher is ok if it works correctly on the right side and with 4-ways on. The hyperflash (2x normal rate) is a safety feature to alert you of a burnt exterior turnsignal bulb. The left side is pulling less current and the flasher senses a bulb is burned out and hyperflashes. As mentioned, try replacing the bulbs or try swapping left bulbs for right bulbs. Also clean the sockets as they can get very oxidized and dirty.

Older 911's and all 914's used a 4-terminal flasher and did mess with the indicators in the tach. This changed somewhere before or in 1986 as my '86 930 had a 3 terminal flasher and does the hyperflash if a bulb is burned out.

I tried swapping both rear and front bulbs between left and right. The problem persists on the right side. So it's probably the socket. But could it be the relay?

Maybe a poor ground on the right side

I agree. It could be any of the physical connections on the left side. This includes the ground wire, the positive and ground connections on either front or rear sockets, the sockets themselves being dirty and oxidized, and the turnsignal switch in the steering wheel.

The left side is pulling just a bit less current than the relay's cutoff for hyperflashing. There's something wrong or dirty connection on the left side. Are the sockets clean? There is an outside chance that the relay's threshold has drifted over time. You can try changing the relay although I'd recommend getting an EP36 LED-compatible relay from your FLAPS or similar retailer. This way if you want to put LEDs in the turnsignals you will be ready to do that. I had to change the flasher relay in my '86 930 when I installed LEDs on the rear of the car.

I recently had a turn signal issue. Long story short I had to clean the contact bumps on the bulb with fine sandpaper.

I've cleaned bulb contacts - didn't do anything. So now I'm thinking either I need to clean out the sockets or there's a short somewhere for real.

Also, not planning to put LEDs on it, just standard bulbs.