RBC

Electrical is far from being my strong suit, and I have an odd situation that I can't figure out.

My gauge cluster went funky, and the usual troubleshooting did nothing to help. The battery and charging circuit test perfectly. I even replaced the ignition switch, given that they're known to fail. Anyway, I was wondering if anyone has seen this before:

1. I'm only getting 11.7 volts at the B1 fuse location, and 12.7 volts at other fuse locations
2. I get 11.7 volts with the key in the accessory position
3. I get 7.5 volts with the key in the ignition position

This is with the gauge cluster removed so I could rule it out as being the issue. Is there anything in the circuit that could cause this scenario at this particular fuse location?

Ahsai

Can you re-do these tests on fuses B1, B2, B3 and B4 (with the fuses in place, undisturbed) since they all get power from the same wire from the current distributor under the dash right side (always hot).
Also take measurements on both ends of each fuse.

RBC

Ok, here we go:

Ignition off:

B1 11.56V
B2 11.49V
B3 Not getting a measurement, numbers on my meter are jumping all over the place
B4 Same as B3

Ignition On:

B1 7.76V
B2 11.44V
B3 Same as B3 above
B4 Same as B4 above

Fuses all check out at 0.

Thanks for the help, very much appreciated!!!!

Ahsai

Any water damage to the fuse box? Per the wiring diagram, all those 4 fuses get power from two 4mm^2 wires (Red/Black) that are connected to the power distributor.
You may want to check the back of the fuse box for those two wires.

RBC

No water damage, the car has never been in the rain.

I'll check the back of the box today. I see there's also a relay in the circuit. Which relay is that, and could it be the culprit?

dcdrechsel

Were the voltage readings the same on each end of the fuses ?

dcdrechsel

OOPs I guess that was your last set of tests

Ahsai

Great question and I also asked for those in my 1st reply. The OP has not provided that. His last set of test was with the ignition ON.

Ahsai

I don't see a relay on that circuit. The fuses are basically wired to the B+ via the power distribution panel.

What year and model is your 996? US or RoW?

RBC

Here are the readings with the ignition off:

B1 11.56V
B2 11.49V
B3 Not getting a measurement, numbers on my meter are jumping all over the place
B4 Same as B3

Could the issue be at the power distributor? I'm baffled by my inability to read voltage at B3 and B4. If I pulled the fuses from all 4 locations, shouldn't I get the same voltage reading across all 4?

Thanks!

RBC

1998 base US spec.

Ahsai

I agree. I'm baffled too. Need to think about it more.

dcdrechsel

Next logical step is to inspect backside of fuse panel and start tracing voltages all from the battery side .It would seem there is a connection issue with the bus

RBC

Thanks guys! I'm not good at electrical, and those Porsche wiring diagrams look like hieroglyphics to me.

I assume I can trace the positive battery lead to something, and go from there. Does all the electrical route through the Power Distributor? If so, I assume I can start there and work towards the fuse box?

My first order of business is to remove the fuse box and inspect the back of it to make sure everything is sorted there.

Really appreciate the help.

dcdrechsel

Since of the 4 fuses are getting power from the same source -pretty good chance problem is at the fuse panel