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Gauge lights not working (except for tach)


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Hey guys, sorry to post on a topic that has probably been discussed, I'm still in the process of searching for info. I haven't found anything relevant yet so I'm posting up in the meantime to see if anyone has any insight.

Problem: gauges do not light up. Namely the speedo and the triple gauges (fuel etc). Everything else lights up including the tach, map light, radio/console, etc.  Except, while trying to fix this issue, my interior turn signals quit working too. The exterior amber lights still flash, but the two small indicator bulbs inside the tach do not.

I've put eyes on the blinker bulbs and three bulbs behind the dash (I think there is only one per gauge, right?) and they aren't burned out. All fuses are good.

Complicating matters: the PO installed two kill switches that I thought might be causing problems. One is very difficult to reach and I'm not sure what it's wired into. The other was spliced into the hot-at-all-times, red/white headlight circuit underneath the steering column. I removed this switch and repaired the wiring; the headlights do work now.

The gauge bulbs are all on a red/blue circuit. Over on the passenger side under the glovebox I found a red/blue female bullet connector unplugged, but I can't find anything to plug it into. Here's a pic. Incidentally, there's also an unplugged black male bullet connector right next to the female. I foolishly tried plugging these together which blew the 10A fuse on the bulb circuit. I've replaced the fuse. Can anyone check to see what this red/blue is supposed to be connected to?
Glovebox.jpg

I found another connector unplugged under the steering column, it appears to have a red and a blue/white wire. I haven't tracked this one down on the wiring diagram yet. Any idea if it's supposed to have a mating connector? It's behind the radio, kind of near the driver's right knee.
Connector.jpg

And lastly here's a pic of the remaining kill switch (red). It has a black wire that's smashed under a nearby bolt (blue). You can also see the two blinker bulbs hanging down (green). This is taken from under the steering column looking straight up. The red/white wire in the lower right corner is where the second switch used to be wired in.
UnderDash.jpg

So questions are:

  • Is the red/blue female bullet connector supposed to be connected to something under the glovebox?
  • Is the red & blue/white two-wire connector supposed to be connected to something under the steering column?
  • What could have caused my blinkers to suddenly stop working - are they somehow related to the gauge lighting?

Thank you very very much for any help!!

PS the car runs and drives normally, the blinker indicators used to work just fine, and I've gotten the gauge lights to flicker in the past but lately they have been completely off all the time. The wiring is stock AFAIK except for the kill switches, and the PO also disabled the seatbelt light/buzzer. I read in another post that the rheostat might be bad, but it seems to work fine: the tach light dims/brightens normally.

Edited by bacarl
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If I was guessing, you have a ground issue. Are you testing your bulbs hanging loose like that? Are you grounding them when testing? Pretty much all of these bulbs ground through the case they are mounted in. Do you have a multi meter to check that you have current coming in?

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I've had numerous problems with my gauge lights.  The sockets get screwed up and the contacts in the socket don't make good contact with the bulb.  MSA's replacement bulbs were too big and rubbed on the inside of the housing.  Some of the sockets have a ground wire attached to the socket itself, some of them ground through the edge of the mounting hole.  Generally, the gauge lights are pain and require special attention to get working right, and installed without knocking something loose.

My complaint might not help you but the point is it could be one of several different possible problems with each bulb.  I had to go through each socket individually.  And one of them still is intermittent.

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3 hours ago, Patcon said:

If I was guessing, you have a ground issue. Are you testing your bulbs hanging loose like that? Are you grounding them when testing? Pretty much all of these bulbs ground through the case they are mounted in. Do you have a multi meter to check that you have current coming in?

Holy crap. You're absolutely right. I didn't realize they grounded through the case, although now that I know that I don't know how else they'd ground, since they only have one power wire. I guess the sockets just popped out of the backs of the gauges one by one (to Zed Head's point about flaky sockets) until only the tach was left to light up.

I put the blinkers and one of the speedo bulbs back in and lo and behold they work fine. Learn something every day.

I do have a multimeter and I was testing the sockets, but since I didn't know how the ground worked I wasn't seeing any voltage. Once I grounded the meter to metal elsewhere on the car I saw the expected voltage at the socket.

Thanks so much guys.

edit: I am still curious about the random red/blue female connector hanging out by the blower motor...

Edited by bacarl
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4 hours ago, bacarl said:

edit: I am still curious about the random red/blue female connector hanging out by the blower motor...

I am not sure this is correct but there is a plug on the harness for optional foglights. It was rarely used...

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