Electrical Gremlins in my Gauge
 

looking for some help and hoping someone has some experience with this...my oil pressure and temperature gauge will light up when i first turn the lights on, but then it intermittenly start to flicker, and then die. then it comes back to life. then dies....rinse and repeat. it's annoying as hell. ALL the other gauges light up and stay lit. i've pulled the gauge, cleaned the contacts and reseated, but it still teases me by coming on as bright as a xmas tree and then performs the black out routine again. it's not the bulbs, so i'm concerned it's something more serious in the wiring...i'm not an electrical engineer, so i'm just looking for other suggestions or ideas on what or where the problem might be. TIA for any advice...

Faulty light swtich? (Probably not) or a faulty ground connection?

thanks.

definitely not a faulty light switch because all the other instrument lights work fine when switched on. it's just the one gauge. "ground connection"? i'll have to research that as i'm not even remotely adept at electrical/electronic trouble shooting.

The gauge backlights are likely all on the same circuit so:

• if you make a jumper wire and bypass some of the connections you may simply bypass the offending wire and your problem goes away/
• Check the ground (brown wire) connections.
• Be suspect of any plugs and sockets on the back of the gauges, hosing them out with electronic contact or electric motor cleaner usually sorts out dirty plug and socket issues..

In any event, the problem is clearly in how power is daisy-chained between the gauges much like a set of Christmas tree lights or a dirty ground wire connection and is localized and not serious and should be easily diagnosed.

https://cimg2.ibsrv.net/gimg/rennlis...66c5cc7889.jpg

thanks for the info...now i need to get a EE guy to walk me through this :surr: because i might as well be staring at hieroglyphics :banghead: i can see the lights are on instrument cluster D=100 #12 and #13 and have some line with 58d/N3 in box; but don't know what i'm looking at...gotta find a YT tutorial for reading schematics.

Hmm - I'll be watching this thread - but I have a slightly different problem - I have no lights at all on my gauges. The gauges work - but no lights! Would love to hear some thoughts on that one as well....

"D=100" may simply be the engineering name for the cluster, not sure, but is not relevant for your purposes
"#12 and #13 and have some line with 58d/N3 in box;" The letter/number in the box points to the coordinate point of where the wire continues on another electrical schematic page in the set of drawings.
On one edge of each page is a series of sequence of numbers and along the other edge a sequence of letters.
I hope you were being facetious about needing an Electrical Engineer to read the drawings as they are really not that complicated.
PM me if you want to discuss getting a set of drawings.
Andy

hi andy thanks. i actually have the entire set of 993 workshop manuals, so i'm sure i can find it. and yep, i was being facetious...the subtext of my comments were meant to convey that i have no idea how to chase sparks, hence my posting of this thread. the wealth of knowledge on this forum is staggering.

I will jump into this boat as well. Several years ago I switched out my stock bulbs for blue LEDs. (Not that that really has anything to due with it)
My fuel, oil pressure and half of my tach gauges do the light dance. Speedo and clock are solid.
I have pulled the gauges a couple times to check it out, but there was nothing obvious.
Tonight I will be jiggling my light switch to see if that does anything.

Actually LED illumination may have something to do with it as LED bulbs are not resistive loads. They are diodes where current only flows in one direction through them. Also, an LED needs almost no current to illuminate so one would have to think through the wiring setup when one puts a diode in each of the lamp sockets. Did you always have the intermittent problem or were the LEDs working properly sometime in the past?
Andy

I installed in '07 and they worked fine until recently.
https://cimg8.ibsrv.net/gimg/rennlis...032c1bdbf6.jpg

yours is the inspiration behind my own decision to move to LED's as well. mine were installed in 2010 and have worked flawlessly for the last 9 years. it is only the oil temp/pressure gauge that is misbehaving. i have a friend with a 95 993 and i'm going to swap gauges with him when he gets back from his vacation. this will let me know whether it's the wiring powering the gauge or something related to the gauge or bulbs themselves.

The rear cover of the oil pressure gauge (like most of the gauges) is a circuit board. Below some pics from the reverse side. You probably have a circuit board problem. When I had an oil pressure gauge problem (the classic tap on the glass to get the gauge to come to life) I cleaned up the pins on the backside of the gauge with strips of pencil eraser. No luck. Desoldered the two center pins of the circuit board so it could be removed, cleaned the pins on the reverse side which had much more sooty buildup, resoldered, and the oil pressure problem was fixed. But now the background lights were inoperable. Couldn't figure it out. At that point I sent it to North Hollywood Speedo. You may end up having to do the same.

Bulbs with the green base are warning lights, tan base are the background lights.