The Official 356Talk Forum

So, my combo gauge was not working for the oil temp and gas level so I took it out and found a black wire which goes to earth out of its bullet connector. I pushed it back in and both needs starting jumping so at least something is happening.

The problem is that all they are doing is jumping back and forth and not showing any real levels. It looks like the fuel gauge already has one of the standard "regulators" to stop the fluttering of the gas level.

So I followed the instructions on here to test both senders and they seem fine (got resistance 46 ohms back for the fuel sender for example).

So I am assuming my gauge is screwed? Could it be anything else?

If my gauge is screwed are there any good 6v repro units? or is it a case of sending off to one of the California gauge guys (NH Speedometer or Palo Alto Speedo?)

Also, has anyone tried the LED bulb kits for gauges as my bulbs are almost invisible in daylight?

Thanks for any advice!

I think the ground wire should be brown ??..

I thought so too but mine is black?

Good pictures of a C Combo gauge wiring here: viewtopic.php?f=1&t=27048

Anyone got pictures of a "B" gauge wiring? I am confused!

In both my case and in the attached picture, the ground wire i think is a ring type connected to a stud off of the back of the gauge, Should be brown.

+1 on brown ground to stud on case.

I have the LED bulbs. Very bright.

Mike

The combo gauge is grounded by the brown wires all porsche's of that era used brown grounds and by the bracket that holds the gauge to the dashboard. Clean the tips of the bracket with a piece of sandpaper and the spot they touch the same way. The fuel gauge (especially on the 61 and earlier cars) tended to wiggle around as the float bounced in the partially filled gas tank. Long ago our electrical grue developed a device to calm this gauge down. The temperature gauge wiggling is probably due to the wires at the sending unit fraying. give the wire a slight tug and it will break. Put on a new end and your situation should be solved. Moving air in the engine compartment was wiggling the wire. al zim

Jim Clement wrote: ↑Fri May 31, 2019 2:44 pm In both my case and in the attached picture, the ground wire i think is a ring type connected to a stud off of the back of the gauge, Should be brown.

In this case, the grounds are attached to female bullet receptacles that are attached as shown in the picture. The brown wire has bullets attached to them and push into the receptacles.
This is a C combo gauge - earlier cars may have the ground attached to the thumb screw posts as stated above.
Porsche kept adding more and more grounds in the harness as the years went by to improve the reliability of the electrical system.

By the way, be very careful removing the bullets from the gauge receptacles - those black risers you see above - as they will snap off in a heartbeat. You kind of have to tease the bullets out … A bit of WD40 and firm grip with needle nose and pull straight out - no angled or side pulling on the wires.

Thanks all, will double check the colour of the ground wire on mine. I will check all the connections as well to see if that helps with the needles jumping

Mike Wilson wrote: ↑Fri May 31, 2019 3:50 pm I have the LED bulbs. Very bright.

Mike

Same got some LEDs and now I can see! No impact on the gauges. Your problem sounds electrical connections (dirty connectors, a wrong connection, faulty earth, or incorrect power-in source) and not related to the gauges per se. On the fuel gauge sender (at the tank) I added, across the sender terminals, an ultra cheap capacitor (0.1 Farad) and it smoothed the operation out, damping transients. Not sure what 'regulator' (?) you have there.

I found this helpful

How did you go David?

Post
by Greg Bryan » Sat Jun 01, 2019 2:24 pm
By the way, be very careful removing the bullets from the gauge receptacles - those black risers you see above - as they will snap off in a heartbeat. You kind of have to tease the bullets out … A bit of WD40 and firm grip with needle nose and pull straight out - no angled or side pulling on the wires.

PLUS 1 on that Greg