Non-Rallye 1968 instrument cluster gas, temp, backlights dead. Limiter did not fix

[cudak888]

Hello all:

I'm currently trying to figure out what seems to be a power issue to my dash cluster. It's a non-Rallye, horizontal cluster setup in a base '68 Satellite/Belvedere.

At present, the ammeter works, along with the turn signals, brake warning lamp, and oil warning lamp. However, the backlights on the cluster are dead, as is the gas gauge and temperature gauge. I swapped in a new solid-state IVR4 limiter into it this evening, to no change (and when I pulled the old one out, I realized it was a new replacement as well - so I'm not the first to try this).

I've already gone through quite a few threads regarding diagnosis, but - before I go tearing apart the dash and possibly chasing after the wrong thing, I wanted to ask if this particular combination of gauge/light failures might indicate an obvious problem/fix (for instance, after looking at the way the PCB is wired, it seems as if the warning lights wouldn't work at all if the voltage limiter was faulty - correct me if I am wrong - and if this is a correct assumption, I could have probably saved myself the effort and cost of the IVR4).

Let me know if anyone has suggestions.

Thanks!

-Kurt

 

[Claytonhc]

Hello all:

I'm currently trying to figure out what seems to be a power issue to my dash cluster. It's a non-Rallye, horizontal cluster setup in a base '68 Satellite/Belvedere.

At present, the ammeter works, along with the turn signals, brake warning lamp, and oil warning lamp. However, the backlights on the cluster are dead, as is the gas gauge and temperature gauge. I swapped in a new solid-state IVR4 limiter into it this evening, to no change (and when I pulled the old one out, I realized it was a new replacement as well - so I'm not the first to try this).

I've already gone through quite a few threads regarding diagnosis, but - before I go tearing apart the dash and possibly chasing after the wrong thing, I wanted to ask if this particular combination of gauge/light failures might indicate an obvious problem/fix (for instance, after looking at the way the PCB is wired, it seems as if the warning lights wouldn't work at all if the voltage limiter was faulty - correct me if I am wrong - and if this is a correct assumption, I could have probably saved myself the effort and cost of the IVR4).

Let me know if anyone has suggestions.

Thanks!

-Kurt

Your gas and temp gauge both run in seeries from your instrument voltage limiter. They should both have a 5V input and get thier ground through your ignition switch. I'm not sure what your cluster actually looks like but if it has the old type circuit board like my 70 super bee you can look through the coating and follow the copper strips to make sure there is no breaks in the circuit. Even a chip or scratch in the dielectric or insulation can mess them up. But I would start by removing the cluster and checking if the casing itself is grounded and then follow the wire to the bulked disconnect. And also check for your 5V input and ground to both with the ignition turned on. Also your back lighting is more than likely a grounding issue. I ran an additional ground on mine to the frame just for good measure. The chrysler bulkhead disconnects are crap so I'd check those too from your limiter. They get hot and dry rot. Do you have those back lights that screw into a circuit board? If you do. You can make a better connection by CAREFULLY tinning the contact ring with solder. Be sure to use Flux

 

[Claytonhc]

Sorry I was typing and looking at the schematic and forgot you already checked some of what I said. Is this about the same schematic you're looking at

 

[miller]

Agree, kinda sounds like a ground issue.
If you do not have a good ground, depending on what material your panel is made of, and how each gauge gets it's ground...through to the body ground. If needed, a separate ground wire from each gauge, can be tied together, leading to one ground wire that goes to the dash/body.

 

[68gtxman]

Dash lights go through the headlight switch. The rheostat in it gets corroded and opens the circuit. Take the headlight switch out, clean and test it and then reinstall it. This is easier that pulling the cluster out.

 

[cudak888]

Just to preface everything - this is the cluster I'm dealing with. I have to remove the entire lower dash pad and switches to get this thing out, so if I can avoid it for now, I'd like to try (and make it to a car show tomorrow - might have to do it blind...again).

1968 Plymouth Satellite (Belvedere) - Seats Removed by cudak888, on Flickr

That said - and correct me if I am wrong - but the ground is picked up through a single pin on the cluster, correct? Member cngordon's diagram indicates such, and the snaking about of the PCB wires indicate the same:

If this were indeed a ground issue, wouldn't the brake, turn, and oil pressure lights be sans-ground as well, as they share the exact same ground feed with the rest of the dash lights? They've been completely reliable, and I would have expected at least a bit of funky operation if the ground was slightly intermittent, or insufficient.

Dash lights go through the headlight switch. The rheostat in it gets corroded and opens the circuit. Take the headlight switch out, clean and test it and then reinstall it. This is easier that pulling the cluster out.

Will take a look - it seems more feasable to me than a bad ground to the lights.

Since the limiter was already replaced, I'm wondering if the gas and temp gauges got fried at one time. This car still has the lousy clickty-clackity mechanical voltage regulator in it.

-Kurt

 

[68gtxman]

Just to preface everything - this is the cluster I'm dealing with. I have to remove the entire lower dash pad and switches to get this thing out, so if I can avoid it for now, I'd like to try (and make it to a car show tomorrow - might have to do it blind...again).

1968 Plymouth Satellite (Belvedere) - Seats Removed by cudak888, on Flickr

That said - and correct me if I am wrong - but the ground is picked up through a single pin on the cluster, correct? Member cngordon's diagram indicates such, and the snaking about of the PCB wires indicate the same:

If this were indeed a ground issue, wouldn't the brake, turn, and oil pressure lights be sans-ground as well, as they share the exact same ground feed with the rest of the dash lights? They've been completely reliable, and I would have expected at least a bit of funky operation if the ground was slightly intermittent, or insufficient.



Will take a look - it seems more feasable to me than a bad ground to the lights.

Since the limiter was already replaced, I'm wondering if the gas and temp gauges got fried at one time. This car still has the lousy clickty-clackity mechanical voltage regulator in it.

-Kurt

Hi Kurt, you are on the right track I believe. After looking at your photo, I realized that I misspoke. It is not the headlight switch, but the panel/dome switch (see the photo below). I don't recall what car I was thinking of, that has the rheostat built into the headlight switch (maybe my previous Chevelle).

Good luck! Bryan

 

[69L48Z27]

Two things come to mind:

- already mentioned but dash light are on that thumb wheel. That is more than likely the problem with the lights.
- I didn't follow your other threads but did you determine if the actual gauges work or not? Gas guage is pretty simple, disconnect your sending unit and ground it, guage should go full. I know my temp guage works 90% of the time. If the gas guage does not move you need to move closer to the cluster and check the sending unit wire for resistance, same with temp sender. If those check out you probably need to take the cluster out and start metering the circuit board.

 

[miller]

but the ground is picked up through a single pin on the cluster, correct?

Sorry! Was thinking on the earlier type boards.
Still would check ground, though. Through the one wire pin, gauge housing to dash, dash to body. Simply because the items not working need ground, however it's hooked up.

 

[bigmanjbmopar]

Your entire cluster is grounded to the frame it mounts to. all the screws that mount it act as a ground.

The circuit board power feed is separate from the lights and turn signals via the ignition switch, key on = power to the cluster guages (voltage reduced by limiter to 5vdc)

"correct me if I am wrong - but the ground is picked up through a single pin on the cluster, correct?"

http://mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerA.JPG
http://mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerB.JPG

 

[cudak888]

Ahh. Good to know.

Since my cluster is a bit discolored, I think I'm going to buy another one, clean it up, and bench test it. With all the problems of getting the old one out, I don't want to have to go back in there!

-Kurt

 

[miller]

Could be just a matter of clean contact surfaces...but, just saying.

 

[cudak888]

Ok - have had the cluster out, put 5V to each gauge, and they pegged. Finally put it all back together in the car with the solid state RT voltage limiter - nothing.

Tested the limiter - it reduces voltage correctly. Also checked the old one; that was putting out 1:1 direct power. Could have fried something.

Went ahead and put 5V to both gauges from a hobby transformer to the leads behind the cluster. Temp gauge moved nicely, gas did not. Might have damaged the gas gauge while doing the voltmeter conversion.

Whatever the case, I disconnected the external power to the temp gauge and ran the car with the multimeter connected to the back of the temp gauge. Went for a drive and got 1.90-1.92v at the gauge for the entire trip - but the needle never moved.

I'm honestly wondering whether I should buy original, used replacements - and probably get shafted with more than a few junk units - or rip into the cluster, redrill the cluster frame, and replace both the gas and temp gauge mechanisms with 12V Sunpro units.

-Kurt

 

[cudak888]

Back to this after ages of procrastination, testing, buying another unit, and finally realizing what the hell was going on.

After trying to bench test everything for the thousandth time with no change in result (definition of insanity, or disgruntled mechanic?) I finally stopped to truly sit back and study the design of the PCB on this thing. That's when I started to wonder about the purpose of the ground prong on the back of the PCB:

...and the old reliable reference (though I should note my wire colors are different on a few of these plugs; positioning is the same):

Until now, I thought that prong's purpose was to be a 12V ground feed into the cluster, until I asked myself "why is there a 12V feed on the PCB if the whole cluster is 12V ground?" And though I still haven't quite understood whether it's really a feed OUT to the brake switch or a feed in, I decided to go to the car, pull the black/ground wire out of the barrel plug, plug it back in, and check.

Lo and behold, the gas gauge started to rise, though slowly. So did the brake light, as always, but it was flashing like a turn signal. My limiter - a solid-state IRV4 from RTE - was flashing at the same speed. I know RTE says the flashing light is the normal operational state, but when I plugged the black wire back in, the light went away entirely, the IRV4's manner of indicating a short.

Then I put my multimeter between chassis ground and the black wire off the barrel plug. Continuity. If anything, it may be feeding 12V into the dash, not taking 6V from the limiter. At least, I hope that's what the intent is. At any rate, I started getting ideas. Not formulated ideas, but ideas nonetheless.

Also, the temp gauge remained unresponsive so I pulled the cluster and started checking some more - and that's when I realized it wouldn't raise up a bit if I put about 6 volts through it for a second or two - but the gas gauge had no problem doing so. And the spare cluster I bought will do so. So I went poking about with the multimeter again, and I find continuity between the inner terminal of the temp gauge (the one fed by the barrel connector) and the body of the instrument cluster.

In other words, a short.

I'll bet anything that I'll find the cardboard isolator toast when I open it up...

-Kurt

 

[cudak888]

Popped the temp gauge out. It wasn't grounding on the shell; it's shorting internally.

And wouldn't you know, the replacement cluster I have does have a working temp gauge, but it looks awful and rusty.

What I wouldn't give to throw it all in the trash and slide another modern gauge behind the stock face...

-Kurt

 

[cudak888]

Ok...here we go again.

Pulled both gas and temp gauges from each cluster. Plugged them into the car, one at a time, using the IRV4 limiter and a jumper from the dash to instrument cluster housing for ground. Brake light, turn signals work as intended.

Then, I slid the temp gauge into each cluster and cinched it down. Nothing. Bad sender? Possibly - not a concern at the moment (yet).

I then pulled the temp gauge and threw the gas gauge in. In both clusters, the brake light started to flash along with the IRV4, and the needle started to pulsate upwards to indicate 3/4 tank of gas - but I realized it was pulsating with the IRV4's LED, as was the brake light.

Then I pulled out a 12V VDO fuel tank gauge that I've had sitting about, wired it into the cluster, and it pulsated with the LED up to 3/4 full, but kept pulsating once it had reached that point - like someone had wired it to a turn signal.

At this point, I didn't know whether to blame the gas gauge or the IRV4, so I pulled the entire dash, wired the VDO gauge to ground and +12V power w/no limiter, and the sender input to the fuel indicator from the barrel connector. The VDO needle powered up from it's spot at rest to "0," but didn't travel any farther. I sent full +12V to the gauge's input for a second, and the needle really quickly sweeped to full.

There's some question whether my gas sender works as indicated, which is why I suspected the 3/4 reading - my theory at this point is that the VDO pulsated up to 3/4 full only because it was receiving phantom +6V power from the IRV4 - the same phantom power that's making the brake warning light flash.

Thoughts?

-Kurt

 

[threewood]

I had gone through some of the same issues. Mine turned out to be pin connectors on the board making shaky contact with the ribbon strips. The board comes off easy from the back so you don't have to pull the dash. Probe each pin for continuity to where it goes. My fix was to clean, flux and solder the pin base to the board.

 

[cudak888]

I had gone through some of the same issues. Mine turned out to be pin connectors on the board making shaky contact with the ribbon strips. The board comes off easy from the back so you don't have to pull the dash. Probe each pin for continuity to where it goes. My fix was to clean, flux and solder the pin base to the board.

Interesting; I had to do that with a few of the pins on the second cluster I was fiddling with - not out of choice. Might solder them all down to see what happens.

-Kurt

 

[threewood]

Interesting; I had to do that with a few of the pins on the second cluster I was fiddling with - not out of choice. Might solder them all down to see what happens. [\QUOTE]

Mine started as one turn signal would randomly stop, or pulse real slow. The gauges would stop working, lights, etc. The pins are crimped so corrosion can get between them and the connection, like a bulb socket. Half had crappy and bouncing continuity or none at all.

 

[cudak888]

Mine started as one turn signal would randomly stop, or pulse real slow. The gauges would stop working, lights, etc. The pins are crimped so corrosion can get between them and the connection, like a bulb socket. Half had crappy and bouncing continuity or none at all.

Here's the thing - I'm getting excellent continuity, that I know. Haven't had anything fizzing or flickering out due to that - everything short of the two gauges get excellent power, and the IRV4 always lights up too.

All the flashing has been definitely been from the limiter.

-Kurt