KeninBlaine

I'm trying again to see if anyone has any suggestions for troubleshooting my intermittent issue of losing power to the fuel gauge, tach, and speedometer. (The clock is fine). It has happened sporadically over the past couple of years, where I'll be driving and notice that the fuel gauge, tach and speedo needles are parked at zero. Often after driving for 5 or 10 minutes, they will suddenly come to life and all is well again, sometimes for months. Since the same symptoms appear if you pull fuse 18 for the instruments, I suspected a quirky fuse, so a couple of months ago I swapped it out and, having had no more issues for a couple of months, assumed I had fixed the issue...... until it happened again today. Changed the fuse and still no go. All else works fine, car runs fine, just the instruments are dead.

I'm wondering if it is a grounding issue, but don't know where to look to check it out. I pulled the gauges out of the dash to check for any connectors back there that might be loose, but it is one big loom that comes into the left side of the dash and tapers down as it feeds each instrument. Does anyone know where the grounding point may be for that circuit (fuse 18)? Or does anyone have any other suggestions?

71-3.0-911

Is it a relay supplied source? I don't know that circuit well enough but I'm imagining it's fed through some relay. Backtrack and try swapping?

pp000830

Hi Kenin,
I think you are onto something with the idea of a grounding issue, maybe a loose ground to the bulb circuit.
Below is a page that will lead you to 993 wiring diagrams.
Wiring Diagrams
After reviewing the appropriate page, looks like sheet 2 or sheet 6, to verify the gauge lights share a common ground I would add a new ground wire and see if your issue disappears.
Also, there is a "Ground Points" page that lists the location of the grounding points called out on the electrical drawings.
The only other part may be the dimmer potentiometer if it also controls the clock that is illuminated than it is not the issue.
If it turns out all the gauges use the same common ground including the clock it suggests that a grounding wire that begins at the clock has an open connection between it and the other gauges. This assumes that the ground wire daisy-chains along the gauge cluster to each gauge.
Andy ;-)

KeninBlaine

Thanks Andy. To be clear, it isn't the gauge lights that stop working, it is the gauges themselves. The lights still work. I have the electronic files for wiring diagrams, but despite having an engineering degree, and despite usually being able to troubleshoot most technical challenges, I find them very difficult to understand. I have no idea how or if the "Central Informer" may be involved in this. I wish the Repair Manual had a description of how the components interact. Will see if I can find the grounding points info and check those, assuming they are reasonably accessible.

KeninBlaine

OK, problem solved. I tightened the ground point behind instrument cluster on left side, but that made no difference (it wasn't loose either). So I tried again by swapping fuse #18 with another one (#21 for right high beam) and voila, all is well again. Interesting that yesterday's fuse swap didn't work, but today's did. And the right high beam works on that swapped fuse. So the fix seems to be either give it time to fix itself, or swap the fuse and hope it works for a while. I may try putting some contact cleaner on all the fuses in case they are getting dirty.

pp000830

Hi Kenin,
Ok.
Yes, the wiring diagrams are hard to read as some of the numbered connection symbols seem to not be adequately defined.

• It looks like each gauge's wiring on the drawings (not the gauge lights). Each has an orange wire that they all share the references the central informer, I believe that relates to triggering the master warning "!" light on the dash. And is unrelated to if the gauge is properly grounded or receiving a signal.
• They also share a brown wire, brown wires are usually the ground wire in our cars, this is probably the wire that has an intermittent connection and should be checked. Using an ohmmeter, not a continuity tester, I would check each brown wire where it attaches to each gauge for continuity to ground and continuity to the other gauges brown wires. This might lead you to a broken connection.
• Also, there is a map of ground wire connections on one of the pages of the wiring diagram. The map seems to indicate the relevant ground connection called GP XV is located behind the instrument cluster to the far left on Left Hand Drive cars. I suspect if you pull the far left gauge out you will discover it.

Hope this helps.

Andy

KeninBlaine

Yes, I tightened ground point XV behind the left gauge cluster. If the issue shows up again, I'll try to check ground continuity from the gauges. Right now I suspect it is a fuse connection issue. I did move the ground wires around the grounding stud while the car was running in case there was a bad connection or wire there, but couldn't make the gauges come to life. Thanks for your help and input.
Ken (in Blaine)

pp000830

Hi Ken,
I guess while I was looking at the drawings and wordsmithing my post above you were able to sort out the issue.
Fantastic!
Andy

KeninBlaine

Woops! Problem reappeared when I started the car today! Tried swapping the fuse. Nope. Tried contact cleaner on the fuse and receptacle. Nope. Then I noticed that when this happens, none of the many colored indicator lights in the gauges illuminate when I turn on the ignition switch. This made me wonder if it is a relay or connection in the fuse panel. So while the car was running, I slapped the top of all the relays and the fuse panel with my hand. When I got back inside, everything was alive again! So it was/is an intermittent connection somewhere in the fuse panel or relay.
Will monitor and report if anything else comes to light with this quirk.

Tarek307

These electrical gremlins are one of the worst things you could try chasing, that and squeaky dash. Good luck man

jay@EZimmoblock.com

Ken-
The 3 instruments you mention and the instrument lights all receive 12V thru relay R11 which closes when the key is in the START or RUN position. The new piece of information you provided about things coming to life after tapping the fuse box is revealing - R11 could be flaky. As a quick test, try swapping R11 and R22, which is the same type relay providing 12V to the power windows. If your windows become intermittent, you found the problem. While you're in there clean the relay pins and sockets too.

pp000830

Hi Ken,
Great observation! I would start with the related relay(s).
Andy

jw1833

Hello,
I've been searching for an issue I am having with my 2019 911 Carrera S... This issue seems very similar to what I have going on. This is my first post, so hopefully will make sense...

In essence, Current state of car is
1) Car starts fine and running
2) PCM comes up, however controls requiring the ignition to be running do not work. For instance - If I select Vehicle setting, The PCM has displays a message which says Start ignition in order to use this system
3) Dashboard cluster does not come on until I hit the trip reset, then goes off after x seconds. Also when I rev the engine, none of the gauges work, tachometer etc

It seems that the communication of the engine actually running to the PCM and dashboard display, gauges is not working..This looked similar to this sentence in post above

"The 3 instruments you mention and the instrument lights all receive 12V thru relay R11 which closes when the key is in the START or RUN position."

Is there something similar to check in the 2019 911 for the 12V issue relay

BTW, - I have checked fuses in driver and passenger compartment

More details about current state - indicating this because in earlier posts had lots of questions on what was working when car running
1) PCM comes on and plays music, will recognize phone and apple play works
2) Dash display will come on when you push illumination button
3) No lights in dash display like seatbelt lights etc
4) HeadLights work
5) Mirrors work
6) Seats adjustment works
7) Middle console - temp display does not work, seat heater, automatic start/stop spoiler etc buttons no lights when buttons pushed Also, sunroof does not open/close
8) Hazard lights work
9) Sterring column, Mode button lighted to sport plus instead of normal, nothing happens when buttons pushed
10) Steering column adjustment works
11) License plate light works

Any thoughts appreciated - Thanks

71-3.0-911

You'll have better luck in the 992 forum. Or 991. I don't know which.