Turn signals and brake lights quit working

[AbbyG]

I have a 1989 Porsche 911 SC and the turn signals and brake lights quit working. The emergency flashers still work which leads me to believe it's not a bulb issue. I replaced one fuse that had blown. Any advice would be much appreciated!

[Michael7810]

Seems like a power issue. I would start by figuring out why the fuse blew or provide more info like which fuse blew and did it go again after you replaced it.

[fintstone]

Need more info. Which fuse was bad and is it all turn signals? Also, the year/model are important.
Are you sure of model and year (as they did not make an SC in 1989)?

[AbbyG]

Thanks for the feedback. I'll check the electrical further. Also, it is a 1979 911 SC. I've owned her for 24 years and my mechanic has closed his shop. I'm doing my own research on this issue that's why I'm here hoping to find some guidance! I have printed a wiring diagram but any other resources would be appreciated.

I just checked the fuse again and the new one blew. I have attached a picture for reference.

[fintstone]

Yes, that fuse is S11 (as expected). It means that you are also losing your back up lights. I think you need to switch to a red fuse (16A). That looks like an 8A. You can double check your owner's manual or the lid from your fuse box and verify.

[EC900]

Just posted a photo of my ‘77 fuse chart owners manual for another topic…if it helps.

[AbbyG]

Thanks, this helps a lot. The car didn't come with an owner's manual, any idea where I can get one?

[Robey5]

unrelated but somehow a bit related…….

An owners manual is available on the FS sub forum, as my car came with like none of that kinda stuff. I bought one from someone who was re-printing them and selling them for the appropriate years…..

With my car, the PO wasn’t real attentive about including a manual, the spare wheel, the jack, the tool kit …. The list goes on here, but I think that you get the idea. Anyhow, you may be able to get a reasonably priced owners manual from our host as well…..

[fintstone]

Yes. Glad he posted that (different than my car). I was going to point out that some of your other fuses were also incorrect...but wanted to fix this problem first. An 8A in a 16A slot should be blowing.

Similarly, the 16A in #6 (which should be 8A) is somewhat risky and does not protect your equipment/wiring properly. Others are off too. You can find them yourself. Just compare your panel with the manual. You start with #1 at the front of the car/panel and count back. The red one is #1.

5 is yellow, 8 is white, 16 is red and 25 is blue.

[AbbyG]

Thanks again for the info!

[geoff_68s]

Does the fuse blow right when it's installed, does it wait until you turn the car on, or does it wait until you activate one of the things on that circuit?

The answer to that question can help you determine where in the circuit it's shorting to ground, which is likely to be the problem.

(in my experience, "right when the fuse is installed" is the least likely, as that circuit probably has to be powered by turning on the ignition, but lots changed in the eleven model years between our cars and I don't have an SC wiring diagram handy)

[geoff_68s]

oh, by the by, there are some wiring diagram scans at

https://msalvetti.smugmug.com/Cars/Porsche/Workshop-Manual-Scans/

I don't know how different '78 and '79 are, but they can't be THAT far off, can they?