GT Instrument grounding

[GT/M]

I just bought my GT and haven't looked into the problem much, but when I turn the car on (electrically, not started) the temp gauge climbs and within a minute or two it's pegged. I was thinking I'd check the sender, but it sounds like this might be the problem.

I'm not very impressed with how Opel did the instrument grounding (all of the grounds tied together on the rusty posts on the back of my speedo, come on!) Do you all think that running an good ground to the gauge would alleviate the problem?

[namba209 (R.I.P.)]

I'm not very impressed with how Opel did the instrument grounding (all of the grounds tied together on the rusty posts on the back of my speedo, come on!) Do you all think that running an good ground to the gauge would alleviate the problem?

Therein lies the source of most electrical problems, not only Opels. A good ground is necessary, as well as a power source for trons to flow. If you were to trace the ground wires from the speedo, you'll find the ground is actually made at the stud that holds up the fuse panel. Which is why it is important to have a really good chassis ground from the battery. Rust and corrosion at the grounding points can wreak havoc on any car. To amplify further, the ground for the headlights is next to the MC forward of the radiator support. Check those for corrosion, rust and tightness too. HTH.

[markandson]

The sender is certainly easy enough to check, I would start there. Why look for ghosts, start at the easy spot and work your way in. My car is not back together yet, but I took the entire dash wiring harness apart, cleaned every single contact point I could find, and then put it all back together. I am trying to avoid exactly what you are running into. In general I am cleaning the entire electrical system, front to back.

[ben]

electrical system issues get a destec wiring chart

[soybean]

When I pulled the dash on mine to add the Cd unit, I'd already experienced the "fun" of bad grounds, esp at the rear for the taillights. I added a terminal block from Mad Electrical products in the engine compartment and ran a ground wire from the negitive side to it. From there I ran a wire to the interior to hook up to the speedo unit, and another to the back to hook up all the ground wires for all the rear. A cheap way to do it would be go to your local Ace, Lowes, and get a Bus bar for an electrical box and use it with a sheetmetal screw to hold it to the firewall and run your grounds to it. Make sure to solder the ends of the wire to the bar and to the connector for the speedo. Hth, Jarrell

[EJprovost]

Those grounds are so important: Had a guy do my wiring, he got something wrong with the ground of the cigarette lighter, it filled the garage with smoke. After that the clock didn't work, then the ignition failed. Then he charged me to do it.

[DESTEC]

GT/M,

I.P. Ground Bus Thoughts: the Tach and Oil gauge share this ground bus, do they work correctly?

Temperature Sender Quick Check (missing everything in between pegs).
Key ON: pull temp sender wire, temp gauge should indicate COLD, ie, pegged LOW. Touch the temp sender wire to the block or valve cover and it will peg the temp gauge HIGH (but yours is already pegged high so this is for future troubleshooting).

IF your temp sender wire (18 blue, red connector pin 5) touches ground or approaches ground potential (insullation breaking down, or moisture etc), that will tend to peg the temp meter high too. HTH.

[tekenaar]

The sender is certainly easy enough to check, I would start there. Why look for ghosts, start at the easy spot and work your way in. My car is not back together yet, but I took the entire dash wiring harness apart, cleaned every single contact point I could find, and then put it all back together. I am trying to avoid exactly what you are running into. In general I am cleaning the entire electrical system, front to back.

I know this thread is concerned with GT ground problems, but you should also check the 4 center main power plus connections, fat red (load) and red/white (source) wires, of the GT fuse panel. Let me suggest, and there's a long story behind this, that you remove the four nuts and star washers from the fuse box's four central studs and remove and clean all the red and red/white wire ring connectors from each post, one at a time, and then reassemble everything in reverse order of disassembly.

The GTs ENTIRE electrical system is powered from these four +12V connector posts!!

[soybean]

Ditto what Otto said about the 4 center main power plus connections. While I was installing the aforementioned CD player, I pulled mine and they were corroded. A small wire brush in a small Dremel tool made quick work of cleaning them. As Otto said "the GTs ENTIRE electrical system is powered from these four +12V connector posts". Keep us posted on what you find to be the cause of your problems.
Jarrell

[jvandyke]

I had my instrument cluster out last night to address some issues. Fixed those but now I have no dash lights. Well, actually the ones that light up the rocker switches/heater controls come on, none of the gauges light up anymore. Bad ground I guess. I'm hoping to avoid pulling the cluster again. I hate that job already! I'll look at the wiring schematic but I won't figure it out, I can't read that stuff. Anyone know off the top of their head what might kill those lights? Maybe I missed one of the grounds to the steering column.

[ronskydivepops]

Maybe the bulbs just aren't pushed in tight enough to make a ground. Looking at my schematic, all the (Grey) wires for the bulbs for the gauges lead to a terminal in between the speedo and amp/oil gauge. Either that, or the darn multi ground on the speedo!! Good luck!!

[soybean]

Unfortunately I'm afraid you will have pull the cluster again. Check the grounds as Ron said, and then add a separate ground from the cluster to the chassis and plug it in to a terminal in between the speedo and amp/oil gauge. I ran a seperate ground from the battery ground terminal all away around the car from the front of the car to the back, and ran feeders for everything that is grounded. Gotta love the "ground gremlins".
Jarrell

[namba209 (R.I.P.)]

If all the instruments are working and other lites work, the arbitrarily it would be the power lead to the instrument lite rocker switch, a Gray/Green wire that also powers the license plate lites from fuse #1. The power source is from either the headlight relay or the parking lite switch that feeds fuse #1. The gage lites are fed by the grey wires from the terminal block between the speedo and the amp/oil gage. HTH.

[jvandyke]

All gages and exterior lights (and rocker switch/heater panel lights) work fine. Just not the gage lights themselves. I checked the grounds on the column, seem fine. License plate lights are working too. Since they do, can I rule out grounds and fuse/power issues and assume the problem is in the rat's nest behind the gages? If I turn on the parking lights, I can see a bit of dim light right throught the "lens" above the switch, the dimmer seems to effect it slightly, that's weird. I guess I'll pull it all apart again.

[GTJIM]

Always put a little 'dob' of di-electric grease on each ground connection - it conducts elctricity - to keep moisture out and corrosion away!

[namba209 (R.I.P.)]

According to my DESTEC schematic, there are two Gray wires from the dimmer rocker that dim or turn on/off the gage and intrument panel lites. one goes to the gang block that powers all the gage lites, the other goes to the lites that reflect off the clear plastic pieces by the cigarrete lighter. Could be one is disconnected. HTH.

[jvandyke]

Looking at my 73 FSM 1J-21 I see the one off the dimmer going up to block between ammeter and speedo, that's probably where it came off, then there's one coming from the fuse box. Don't see where the "cigarette lighter" lights get their own feed but whatever, in I go again......ugh.

Now I think I see some more wires in the schematic.

[ronskydivepops]

After awhile, pulling the dash is as easy as opening a can of beer! The fun part is putting it back together. Good thing I quit drinking!! Honestly, it gets easier each time. You remember where it hangs up, and which way to push/twist/and bend to get it back in place. Try it with a wooden overlay over the instrument panel, and it really gets to be fun.

[jvandyke]

This'll be three times pulling it. Y'aknow I can look up in there and see the wires on the dimmer and pretty sure I can see where it goes. Don't see anything loose. Hmmmmmm

[jvandyke]

It was the gray wire from the dimmer to the block by the speedo.
All is well. I managed to re-break one of the things I went in to fix originally.
(broken mounting lug for flasher switch assembly, epoxied it up and it WAS good, but I broke it loose again).
No big deal. It really isn't that bad a job I guess.