Dash gauges trial and error

[Innoi]

First off I am a new owner of a 1969 Dodge Coronet. I have wanted one for 15 plus years and finally became a proud owner of one a couple of months ago. Great car, tons of fun. I bought a running drivable car but it does need a couple of things here and there in my mind just to keep it road worthy.

Anyways one of the areas that keeps nagging on me to fix is the dash, gauges. I have the standard 120 square style with no clock or factory tach. The previous owner put a bolt on tach on the dash that works, and also the typical 3 gauge under dash setup with oil/alternator/temp gauges that all work.

I want to get the original dash back working and maybe add in the stock tach to the cluster. My first plan of attack was to inspect the wires and see what was what. I'm new at this stuff but my wire harness from under the dash looked pretty good, it actually looked untouched. I checked the fuel tank and followed the blue wire all the way to under the dash, no issues or breaks. So it all looked pretty good to me so far. I checked the tach and saw the typical splice fitting on the coil wire but it looked good. I couldn't find or just was not looking in the right area for the alternator wires but I'm assuming since the new gauge works the wires are good. I don't have a bunch of extra wires going everywhere under the hood, which is good.

I did a little research and saw that some of the dash problems could be related to a bad voltage limiter. So I ordered one online, seemed like a reasonable place to start for my gauge issue. Put the new one in, fit perfectly and rechecked the gauges. No change. Every thing still worked but just not my original gauges. I checked the fuse box and all my fuses looked good. One thing I forgot to mention is that the cluster does light up when I turn on the headlights, so that is good.

Just wondering what my next step should be? My main concern is to get the fuel gauge working because it sucks driving somewhere and always filling up the tank because I think I'm going to run out of gas.

 

[Seventy]

I would down load a wiring schematic (mymopar.com has a lot of them)
then start tracing.

Does the speedo work? That would be the first thing I fix sinc maybe the easiest.

Does the amp meter work? them 2 are stand alone so should do something...

your cluster looks like this?
http://www.ebay.com/itm/1968-69-PLY...GES-NON-RALLYE-CORONET-MOPAR-68-/141750488805

I would pull it and test it out of the dash, trace all the tracks on the printed board...

Them tachs are tough finds, I know my father ended up buying an entire restored cluster with tach for $850 shipped vs a tach for $350, then he sold his cluster for a few hundred so it was worth it for a restored unit...
something to keep in mind...

 

[Innoi]

I did print out the wiring schematic, but I am a bit overwhelmed just looking at it. Yes my speedo works and no the amp meter does not work on the dash. The only thing that works on the dash is the speedo and the lights when I turn them on. Nothing else works, not the amp meter, temp or the fuel gauge.

Pulling out the dash, is that hard? I guess if I know where all the screws are it shouldn't be that big of a problem. Could anyone give me a rundown on how to get the dash out?

I know its going to be hard to find one of those tachs at a reasonable price but I figured it was the best way to go. I guess I could just take it all out and put in Rally gauges, but again that would probably cost more.

 

[440roadrunner]

Pulling a cluster is not difficult, just be careful. On some cars, it is much much easier if you drop the column down.

So far as gauge troubles, there "can be" many. I try to get guys to think of them as a "system."

First problem area is the PC board harness connector pins which come loose or break. You either mus solder / repair them, or pop for new PC boards.

The IVR. Get a new "solid state" one, the old ones were mechanical, like a flasher. Also, the brass spring fingers into which they fit in the PC board may not be making contact with the PC board traces. You have to solder jumpers across.

Gauge studs. Gauges are connected to the board with "fake nuts." Consider replacing with "real" ones, and work them back and forth to clean / scrub the board and then tighten.

Gauges. How old,? again? are these girls. The gauges may not be working or "in calibration."

You can scare up resistors to check them. Since RadioShit went downhill, probably find them on ebay, Digikey, or Mouser electronics. All gauges, oil, temp, and fuel, have the same actual gauge and sender resistance.

Resistances are

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

If you look in the shop manual, chapter 8, there is reference to a Chrysler gauge test tool. That box is nothing more than a switchbox with resistors similar to those

The cluster MUST be grounded. It pays to add a ground wire and bolt it to the dash frame or column support

As mentioned, get a shop manual if you do not. MyMopar has them for free


ALSO even if you don't do this "mod" please read this Mad Electrical article which gives a very good insight on problems with the wiring in these, adding larger alternators, and the firewall / bulkhead connector and ammeter

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

 

[Garys1969RR]

I am having similar issues on a 69 RR I just bought. Fuel gauge and temp gauge wont work. I plan to remove the cluster and check the pin connectors, gauges etc. The last one I did was difficult to get out, mainly the switch panel below the speedo. I had it worked over by a local Mopar shop and now it all works. Good luck!

 

[Innoi]

Thanks for the great feedback. I will try and pull our the cluster and start there. Hopefully its not a scorcher today in Southern California, I don't want to die of heat stroke while working in the driveway.

 

[kevin403]

I would check ground first. Do the easiest things then the hardest. Are you comfortable with a volt meter. If you have to check grounds you can just make a simple jumper wire with a couple of alligator clips...

 

[furyus]

The part where Road runner said about the fake nuts was my problem. To look at the nuts, and threads, all looked fine. After cleaning the threads, and using regular style nuts, my gauges worked. Fuel has to have a ground strap from the sending unit to the steel part of the fuel line. You can ground it anywhere, but it needs a ground. You are not going to find one problem, and all will be fixed. If you haven't removed the dash, temporarily ground the wire to the fuel sender. It should read full. If it does, it's the sending unit. If not, it's in the dash/wiring.

 

[Innoi]

How would I do that? Make a ground wire and attach it on the fuel sending unit? where on the sending unit do I attach it? and assuming I do that I should see my fuel gauge move.

Where would I find the ground wire on the dash cluster? or can I make one and attach it from the cluster? if so where can I do this?

 

[440roadrunner]

So far as a cluster ground, any of the screws on the PC board that mount it to the housing are ground. If you can provide a photo, I could show you

So far as the sender, remember that the tank is not particularly grounded, it sits against a pad between the tank and body, held by "rusty" straps.

The sender is not grounded to the tank, particularly well. There's a gasket, and the lock ring might be rusty / corroded.

Originally the ground for the sender was by means of a spring clip jumpering the sender tube over the rubber connector and clamped to the fuel tube "to the front." THAT was not particularly grounded EITHER as it's "clipped" to the bottom of the body with spring clips!!!

So it was all "accidental." Bear in mind, "Mr Plymouth" never intended these cars to even exist, 50 years later.

If you have a "big ***" soldering iron/ gun, you could solder a pigtail wire to the fuel outlettube. I'm pretty "back yard" I simply scraped it clean, wrapped the pigtail around the outlet tube, and put a worm drive clamp over the top.