1987 944s turn signal/tail lights issue

Bdude93 · 08-01-2025, 05:41 AM

Hello,
New 944 owner, first time post. It was brought to my attention at a traffic light last night that my drivers side taillight was acting weird and flickering. I pull over to check it out and what’s happening is, when the headlights/taillights are on and I turn on the drivers side turn signal, in the rear, the tail and rear side marker lights are alternating with the turn signal flashing. This does not occur on the passenger side or when the headlights are not on during the day. What’s weirder is if i disconnect the taillight harness on the drivers side and plug back in, turn the turn signal back on, it will work fine. But as soon as you turn them off, then on again, its back to the alternating flashing. I have not been able to find any info on this. If anyone has any idea what i could do or point me in a direction of what the problem might be, it’s much appreciated

Brandon

kdjones2000 · kdjones2000's Garage

I would replace your relay for the flasher and see if that fixes it.

It should be in the fuse box under the hood.

Bdude93 · 08-02-2025, 04:48 AM

Quote:

Originally Posted by kdjones2000

I would replace your relay for the flasher and see if that fixes it.

It should be in the fuse box under the hood.

That was my first thought, butI figured if it was the relay, wouldn’t it affect both sides? I don’t know. Guess I’ll give that a go first.
Thanks

originalowner · 08-02-2025, 06:34 AM

Before you buy a relay, check the ground for that taillight module. And the relay does both sides, so don't buy one at all.

Also, check the ground wire (brown) going through the connector since fiddling with the connector temporarily fixed it.

Jfrahm · 08-02-2025, 08:50 AM

Check the bulbs for worn contacts, clean the harness contacts, bend if sloppy.
The solder contacts on bulbs can wear out from vibration and time.

Legit Salvage · 08-06-2025, 04:52 AM

TLDR: replace your bulbs (or at least check the sockets).

I had a not dissimilar problem in an old honda. Everytime I would hit the brakes the exterior running lights and dash lights would come on. After several attempts to find the short I replaced the bulbs. Turns out one of the dual filament bulbs had blown and the top filament (the brake light filament) had disconnected at one end and dropped down and was touching the running light filament. Anytime I hit the brakes it was energizing the running lights through the touching filaments.

Not saying this is your exact problem but it seems like something is shorting at the bulb or socket.