My 78' gauges have never realy worked. The fuel gauge used to read intermittently (accuracy was in question) and would drop to 'E' after going over a bump.
Anyway, my printed circuit is burned out at the clock wich I understand is common. The dash lights as well as brake and highbeam lights work.
I just put in new fuel, water, oil gauges today with no luck. I already went the cheap route and installed new sending units for water and oil some time ago. Havent checked fuses but I figured since lights work, its getting power to the cluster. Anybody ever have a similar prob?

Thanx in advance for any help given

J.Lansing
Texas

That %#&@ connector between the printed circuit and the wire harness is the most usual culprit when you have dash guage problems on a 5th Gen.

would'nt that affect the dash lights as well?
When I installed the new sending units for the oil and water I got an initial "twitch" in the needles for the first day or two when starting the car.

-J-

There are several power and grounds going into the connector and one of those runs the lights plus, IIRC, one of the gauges.

What you need to do is to carefully rub the copper traces of the connector using an ordinary pencil eraser. Brush off the crumbs with a very clean rag. DO NOT attempt to "lubricate" the traces.

Make sure the nuts on the gage studs are barely more than finger-tight; they don't have to be any tighter than that. You usually find them finger-loose from the factory or just plain loose; tighten them just a bit more than that, after carefully cleaning the copper traces under the studs/nuts with the pencil eraser.

You can test the gage panel by simply inserting it back into the pod without having to bolt it in place, and see whether everything is working.

There is a ground wire that is connected to the panel's ground and that is one of the two ground wires with a large 3/8" ring terminal, that has to be grounded to the left dash support strap. The 2nd ground wire goes into the harness (actually, I guess both ground wires go into the harness but one then comes out to the dash pod connector while the other goes to all the black wires inside the harness that are ground). It's barely possible that that dash support bracket strap is not bolted tightly to the firewall and so is no longer providing a good ground; if so, it may feel loose. What you can do is move the ring terminal around under the dash and try grounding it to the brake pedal support bracket, which is also grounded.

Also, you MUST have the ground straps attached between the back of each engine head and the firewall; those straps ground the battery negative to the car body. Without those straps, the body can only obtain a ground through other things like the transmission linkage (or cable), brake lines, exhaust pipes and hangers, etc. Those straps are CRITICAL. Without them, all the current that the body electrics need will try to flow through the other items mentioned. And if you have happened to move your battery negative cable to the frame or fender, then all the starter current will have to first flow through the frame or fender, then through the exhaust pipes and hangers, tranny lines and shifter linkage or cable, and brake lines. That's why some guys burn up their shifter cables: they move the negative cable from the engine block to the frame or body and don't provide a good connection between the frame or body and block.

The "burned traces" around the clock shouldn't affect much unless the gages/lights also get power or ground through them; I don't rember whether they do. Here's a page showing how some folks have to hardwire the gages when the circuit "board" has delaminated too much:
http://members.dandy.net/~k0xp/Oldsmobile/HardwireChevyGagePanel-a.htm

ok, I do remember that after the engine was installed, and the elky was getting its new tranny, the owner noticed that the ground strap wasnt attached to the firewall! But I only remember one large strap from the left rear of the block. This weekend, I'm going to look at all these things that have been suggested. The link to the hotwire gauges was impressive and very easy for a shade tree mechanic like me to understand. That will be my last resort though as the printed circuit was, as I remember, in pretty good shape. Thanks again and I'll post a summery of what works or doesnt sunday or monday

Thanks again gentlemen.

J.Lansing

Yes, I seem to recall someone else also told me there is only one ground strap on the Elkies. More won't hurt, though, especially if you've installed lots of interior gadgets like a high-power stereo or whatever.

Glad the hardwire page was that clear; it's been a year since I last looked at it, myself ;o) By the way, your own gage panel may well have different-colored "resistors" mounted on the back side of a gage; they were chosen at the factory to match the particular sender installed in the car. Once, I made some measurements of some temp sensors and several different gage panels; the results are here:
http://members.dandy.net/~k0xp/Oldsmobile/OldsCooling/TempSensor-GageAccuracy.htm

There was no real "surprise" found during the measurements, other than that all the various gages and sensors appeared to be fairly close to one another. I could not measure oil pressure sensors, however, and strongly suspect that those big can types from GM tend to change significantly over time. When you're in doubt about the reading of an oil pressure gage, check it by comparing it against another one.

Let us know whether you can get your gages working. Come back right away if you still have problems and probably, it being a holiday weekend, some of us may be here to give you timely advice.

you can bet that I'll have a post by sunday evening at the latest.

-J-

I have a '78 as well and did the same thing there for awhile after I rewired the thing. This is what happened. I only had the bolted in temporarly so everything would not jiggle around a bit. That was what was causing it. The fuel gauge would go to empty and other gauges wouldn't even be accurate. You have to make sure that the plug itself is fully secured in position and will not back out of its mounting hole. After that is done make sure the Pod is mounted in securely and tightly. Make sure that the plug mated up with the Pod properly. If done correctly your problems should be eliminated.

Hello: The dash cluster is a printed circuit as you well know. It is poor at best, but thats the way it is. It plugs into a Male connector mounted in the dash itself. The dash connector is mounted in a protrusion that sticks out of the dash assy, but is supported only on one end, the right end. As time goes by the support for the dash connector starts to move toward the front of the car, mostly on the left side of the connector. After many moon the instruments or lamps start doing funny things. Not all will fail at once, some may work. Pull the instrument pod and clean all the contacts thoroughly, but be careful not to damage the printed circuit. You may have to get a piece of rubber (old radiator mount) and cut it to fit between the left end of the dash plug and the column support brackets. This will push the dash connector toward the rear of the car and provide better depth of mesh with the dash printed circuit. Give that a look see and you will probably discover that is your problem.
good luck
Darryl....

The connector for the printed circuit "board" IS supported on BOTH ends, not just one. At least, "good" ones are. I don't doubt that one that's been removed several times may have worn out the plastic notchy-type support, though.

ok,
I just spent 6 hours working on the inst cluster. Yes...the connections for the printed circuit and the dash mail plug were FILTHY! I Cleaned both sides and reconnected with all new gauges except the volt meter. After some time fiddle f###ing with the dash, I turned the key...
YEEHAAAAWWW! as we say here in TX. all the gauges came to life!
I noticed the volt meter at "12 O'clock" 13 and drop a little when I started the engine. As the engine ran the voltmeter sloooowly creaped down. Turning on the lights just made it drop more. (NOTE) I HAD AN ALTERNATOR PROBLEM LAST YEAR, THE ALT WAS ONLY GIVING OUT LOW CURRENT AND THE BATT. WENT TITS UP. I BOUT A NEW ALT. AND INSTALLED, JUMPED THE ELKY AND LET IT CHARGE BUT NEVER REPLACED THE BATT. HAVE NEVER HAD PROBLEMS WITH IT THOUGH.
So, I start thinking and decide to install old gauges and sure enough, they worked. I go to wally world for a test drive after total reassembly and just when i park, the gauges go ****ty again!
I come out, get in the car, hit the ign. and gauges are fine. Half way home, they go ape **** again. Also the dome lite workes but no longer when i open door. (probably have to work the plug in some more. Would be nice though if i could find an accurate wiring diagram) All else is the same as before. Found 1 large ground under where the light switch is attached to the dash support so I assume thats the main ground for the dash wiring. So I'm thinking I have to somehow get that connector to hold better against the printed circuit such as the post I got to this subject post.
I mapped out the printed circuit and NOTHING...I mean NOTHING even remotely resembles ANY wiring diagram for this elky. Not the colors or the location of the plugs to the printed circuit. is there a wiring diagram out there somewhere that is remotely accurate? I pretty sure the wiring is stock and not tampered with. It makes the job almost impossible to do.
The only thing I can think of is the guy who bought it ordered all the bells and whistles, etc.
Anyway...any thoughts anyone???

-J-

You have a '78, and perhaps things changed slightly in the wiring compared to '79+. I recently went through my '79's dash completely.... removed the whole dash, traced out the entire wiring harness, etc. etc. and it agreed completely with the 1979 Elky/MC/Malibu diagrams from Chevy. I would certainly trust the original Chevy diagrams before trusting anything from Haynes, Chilton, etc.

If your cruck originally had idiot lights instead of gages, that could be the source of the confusion since a cupla wires are different between the two. That may be even more true of the '78, I don't know. Where are you getting these diagrams from? Is your harness still wrapped with the black tape, as the factory did? Most folks, when they tear into their harness, take the easy way out and don't bother to re-wrap with that stuff. That stuff is available new from OPG, BTW.

I take it that when your gages went apeshooey on the trip to WallyWorld, ALL of them went nuts?? That indicates a ground problem, for sure: either at the connector or wherever the ground wire in the connector is going. I'd concentrate on that. Obviously, it's a common wire with all the gages; and if they all read SOMETHING, then you're obviously getting battery power to them. So that leaves a missing ground. If the illumination lights remain lit, then they are obviously still getting a good ground connection from somewhere. They get their power from the rheostat in the headlight switch so that source of power is different from the gages, which should be getting battery voltage with the ign switch on.

As for your courtesy lights: I have the same intermittent problem with my right door switch; just haven't gotten around to doing anything about it yet. The driver's door switch is reliable, as is the headlight switch's courtesy position. I haven't looked but possibly, the switch has a wire ground and that, too, has become intermittent.