My fuse #25 in my GTS regularly blows with no apparent reason.

Can anyone help with troubleshooting,



An electrical failure in a 928 is a flawless recipe for a headache job.

Ok, fuse 25 is fed by the 30-bus, so direct battery power.
It exits the CEB through connector F11 as well as F12.
F11 feeds:
- Instrument cluster on pins 16+17 of plug 2
- Pin 3 on T23, this feeds the PSD ECU on pin 11.
- Ignition lock pin 2, which feeds on cluster plug 1 pin 1 (Buzzer, not used in EU) and the timer relay pin 85 (ensures that automatic interior lighting goes off when you turn the ignition.
- Bridge on the CEB from F11 to F23 and then via S6 to power unlock tailgate pull switch (next to seat) Tailgate lights, against roof lights
F12 feeds:
- Diagnostic connector pin 12
- Interior door lights and door lock lights.

You can measure with an ammeter if the 7.5 is tight when the lights are on. A little tricky, but you could temporarily replace the 7.5A fuse with 10A if it turns out that the 7.5A is tight. If the problem comes back then go back to 7.5 and continue your search.

Trouble shooting is eliminating. The PSD ECU can be easily disconnected. Pull 1 connector.... You will get alarm in cluster that PSD is not working but you can just drive as if it is a car without PSD.

Check interior lighting by disconnecting F12 and S6.

I think you can also remove the timer relay (not sure).

Cluster could also have a defect, I have seen that the power supply part had a defect. Very difficult to troubleshoot.

Then cabling issues remain.

Good luck with troubleshooting.
1992 Porsche 928 GTS Midnight blue
The Netherlands