The firewall side of the fuse is coming from the switch, flasher, etc.
The forward half of the fuse is going to the light.

When checking on this, I noticed that the spades of the fuse are accessible from the top of the fuse...with a known blown fuse, you can get the reading from the light circuit.

Thanks for your input about the small bulb all my bulbs are from 1989 an when I took out the rear taillight
the small bulb it was very dark brown an would not light up so I order all of the light bulbs so that I could put in all new light bulbs in my car. Pelican sent me the bulbs in two days an all my lights are so much better now. I did clean up my were my bulbs go in they were not to bad but they did need to be clean up. I am sure you are right about the small bulb blowing #33 fuse. Also my relay for this system was 23 years old so I put a new one in an everything is just like new now. Vernon

problem solved!!!!!!! after being slow at work this afternoon i pulled in my car and with the help of a co worker we went about trying to find short causing rear passenger turn signal to blow the fuse as soon as signal activated. Well i brought out the wiring schematic and we looked at it and started at the fuse box. The schematic is a little blurry when zoomed in. Any how on the rear tail circuit there is a blk/gr wire that runs from rear assembly to central electric where it splits off to side marker harness it appeared to read as connector O pin 22 .Well let be the first to say that is not it is actually connector D row 2 pin 2 hence the 22 on schematic on the back of the fuse box. Well after going here and testing we found high resistance showing on meter so we cut the wire where it splits in to the 2 circuits 1 goes to rear tail light and 1 goes to side marker. Applied a fused 12 source to both wires and checked to see if rear light came on without popping fuse and bing one wire popped fuse other gave me a working turn signal to rear. So i left the side marker harnes unhooked and connected back the blk/gr going to the rear with solder and shrink wrap and now i am glad to say my rear tail light is now operating normally. I must have a short or corrosion in the harness that is in the front passeger fender that was causing the short.

i must say i am extremely happy this issue is resolved cause it's not that it was preventing me from driving but was driving me nuts that i knew there was this flaw and it was a little disappointing to know it wouldn't work properly.

Good for you! I have had my 964 for 12 years they are very well made an for me this was the frist time that I had something go bad on my lights on the car. Over all we have a lot of snow hear in Tahoe I drive it all winter an for 12 years it has never let me down in snow an ice one time just a great porsche. Vernon.

Can you post the wiring diagram? Or a link to it's location, this problem has had me stumped for days.....

Had the exact same problem on my 1990 C2. Want to thank you for your thorough trouble shooting
and post, as turn indicator is not frying the fuse now. Thought about looking into rewiring side marker that's eliminated, but may put that lower on priorities......... Thanks again

I have the same problem, again looks like the issue is the unused wiring for the side marker, has anyone ever traced out and found where the unused wiring is actually going. This is my goal, I was tracing the wiring from D22 ( c2 1991 wiring diagram)2 gr/bk wires, one wire goes back to rear taillight the other one I can't figure out, if anyone had the harness apart or has figured out where it goes. Would be great so I don't have to cut the wire and really find out where this short is coming from. My vehicle is mostly apart for the next week or two, so I will keep trying to trace it out. I also tried a wire tracer but the signal disapears as soon as it's connected leading me to believe the wire goes to a device with resistance.

Found it, just above the passenger wheel well inside the frunk, two connectors were dangling, I attached the wrong one to the hood light, caused the short. Now unplugged that and plugged in the right one, everything back to normal.

I found this thread very helpful as I ran into the same issue as Maxpowers2k as the connector to the hood light was attached incorrectly and was creating the short. Lesson learned, always check the connections and look at the wire colors on the schematic. Thanks Rennlisters