68 Charger - Gauges not working

[mrandig]

Since the '68 Charger is finally running, I decided it's time for my second post here.

I've got the usual gauge issues - no fuel, no temp, no oil pressure. In addition, my clock isn't working either. Amp gauge is fine, tach is fine, radio works, flashers are good, etc.

I traced 12v power almost all of the way to the circuit board, so I'm going to assume that the voltage limiter needs to be replaced to get the gauges working again. Either that, or each sender is bad, which I highly doubt. If that is the case, I guess we'll find out once the new RTE Limiter (IVR4) gets here.

So, I'm assuming that the new RTE Limiter will fix my problems, and that I can actually do this swap laying on my back, blind, by using only touch and feel. All the while, working around the vintage air system which is conveniently in the way.

As for the clock, what am I looking for here? I'm assuming this is an unrelated issue to the gauges. It's late and my eyes are tired, but the only power source I see, based on the service manual diagram, is tied into the light switch? I would have thought that was an instrument lamp, but that's shown as a separate circuit...

 

[1968rt]

Did you make sure the cluster is grounded? Instrument Panel Grounding Tips Mopar Plymouth Dodge

 

[Car #4]

Is it a tic tic tach? That’s what I have and the clock doesn’t work. There’s power on the wire supplying power to the clock so I’m guessing it’s something internal, but I could be wrong. Don’t know a lot about this stuff. Interesting, and I know this sounds crazy, but before it quit working completely the second hand would run in both directions! That’s right, it actually ran in reverse at times and more than once I’ve seen it switch from reverse to forward while I was driving.

 

[mrandig]

Did you make sure the cluster is grounded? Instrument Panel Grounding Tips Mopar Plymouth Dodge

The wiring diagram from the service manual is doing my head in. Best I can tell, the instrument ground is at the Voltage Limiter, which seems to go nowhere?

I'm guessing that "nowhere" means that the board is grounded to the instrument cluster which is grounded to the dash frame? I don't see any wire grounds leading anywhere...If so, then the grounds are OK.

*Edit - I just clicked the link in your post, and confirmed this is the case. The cluster does ground to the dash frame. Thanks for the info!

 

[mrandig]

Is it a tic tic tach? That’s what I have and the clock doesn’t work. There’s power on the wire supplying power to the clock so I’m guessing it’s something internal, but I could be wrong. Don’t know a lot about this stuff. Interesting, and I know this sounds crazy, but before it quit working completely the second hand would run in both directions! That’s right, it actually ran in reverse at times and more than once I’ve seen it switch from reverse to forward while I was driving.

It is a tic-tock-tach. Coolest thing ever. I have no clue either why it doesn't work. I can understand why the gauges don't, but I'm under the impression they're not related issues. The clock should work...

 

[Car #4]

It is a tic-tock-tach. Coolest thing ever. I have no clue either why it doesn't work. I can understand why the gauges don't, but I'm under the impression they're not related issues. The clock should work...

My gauges work but not the clock which would support your theory.

 

[BLK 68 R/T]

It's pretty common for the clock to not work. Sometimes playing with the clock adjustment knob will get them going - for how long is a crapshoot. Most likely it will need pulled and completely taken apart, cleaned, lubed and put back together. Or you can send it out for rebuild.

 

[mrandig]

It's pretty common for the clock to not work. Sometimes playing with the clock adjustment knob will get them going - for how long is a crapshoot. Most likely it will need pulled and completely taken apart, cleaned, lubed and put back together. Or you can send it out for rebuild.

Since my wife accuses me of always being late, I guess I don't need to worry about what time it is anyways. Oh, and I have an iPhone.

Fingers crossed the other gauges work with the new voltage limiter. I would like to know how much gas I have left, not to mention the other important stuff.

 

[mrandig]

I received the new Voltage Limiter a few days ago. it's hard to tell, but the original had definitely seen better days.

Old...

And New....

The new one also has a flashing red led to let me know it's working.

I don't know how many wires I disconnected trying to get this installed by touch. I guess we'll see.

Results to follow.

 

[mrandig]

Looks like the oil pressure gauge is back working. Not sure about the fuel, since I don't know how much gas was in the car.

Water temp isn't working yet, however. I guess even one out of three working aint bad at this point...

I also found a light bulb. Not sure where this goes, but obviously I'm now missing one. Oddly enough, it seems that everything is lit up OK.

I doubt it's a spare lol.

 

[70gtx440dana]

There are 3 of those bulbs that twist into back of instrument cluster behind small gauges.

 

[mrandig]

There are 3 of those bulbs that twist into back of instrument cluster behind small gauges. View attachment 1662584

I'm going to guess it's the one directly above the voltage limiter. The other two are in place for sure.

Doesn't matter at the moment, as the bulb is dead also. I'll have to add this to my list of to-dos.

 

[70gtx440dana]

Correct factory bulb is #158

 

[jimbosride]

It's pretty common for the clock to not work. Sometimes playing with the clock adjustment knob will get them going - for how long is a crapshoot. Most likely it will need pulled and completely taken apart, cleaned, lubed and put back together. Or you can send it out for rebuild.

Now I'm no expert but this is what I did.
I found a clock for my 65. I put it on the bench and hooked it up to a power supply and then manual start the movement wheel. If it runs for
any time and stops apply watch or singer oil to the gears and pins. Keep working with it to get it to run longer. If its a power issue the spring wind contacts maybe dead then not sure what to do. I find that allot of the clocks dry out in hot cars over time. My guess you would get 2 years on one when the car was new.

 

[BLK 68 R/T]

Looks like the oil pressure gauge is back working. Not sure about the fuel, since I don't know how much gas was in the car.

Water temp isn't working yet, however. I guess even one out of three working aint bad at this point...

View attachment 1662576

I also found a light bulb. Not sure where this goes, but obviously I'm now missing one. Oddly enough, it seems that everything is lit up OK.

I doubt it's a spare lol.

View attachment 1662577

With the ignition on you can temporarily ground the water temp sending unit wire, the gauge should move towards the hot side if it’s working. Only do this for a few seconds though.

 

[mrandig]

With the ignition on you can temporarily ground the water temp sending unit wire, the gauge should move towards the hot side if it’s working. Only do this for a few seconds though.

Yeah, there's nothing. Gauge is pegged well below "0" and doesn't show any signs of movement.

I think I'm going to have to test the entire circuit from sender to gauge, for both the water and fuel.

I'm almost willing to bet I'm going to need two new gauges.

 

[BLK 68 R/T]

The fuel gauge looks like it might be working in your picture? If you have a test light, pull the wire off the fuel tank sending unit. The light should pulse on and off. If so, add 5 gallons of gas and see it comes up past 1/4 tank a little bit. Water temp gauge is most likely bad.

 

[mrandig]

The fuel gauge looks like it might be working in your picture? If you have a test light, pull the wire off the fuel tank sending unit. The light should pulse on and off. If so, add 5 gallons of gas and see it comes up past 1/4 tank a little bit. Water temp gauge is most likely bad.

It did! The fuel gauge had sneaked up slightly above "E"; I just didn't notice. So, it's totally inaccurate, but it is working.

Nice catch.

 

[mrandig]

5 gallons of gas didn't move the needle much, but at least the gauge is reading.

Now, if this car has a 25-gallon tank, it may be accurate. Otherwise, I just need to get gas once it starts getting close to "E".

 

[BLK 68 R/T]

Think they are 18 gallon tanks.