Brake light on, Fuel & Temp gauge pegged to the right.

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gunbunny

gunbunny

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1974 Plymouth Duster /6 base.
Getting the Duster out for the season, brake light is on. I check the master cylinder, no issues.
Light will flicker.
Yesterday, did oil change, pulled the valve cover to repaint, and fix fuel line leak.
Drove the car real quick, and the fuel read empty, and the temp gauge was inop. The oil light was on as well. Looked, realized the oil sender wire was knocked off during filter change. Put wire back on sender.
Shut down the car and now, the brake light is on full time and the fuel gauge and temp gauge are pegged to the right side.
I've not taken any reading yet.
Any suggestions before I start taking every thing apart
 
Do you have a spare ignition switch? If so, you can unplug the existing one under the column and plug in the spare. Then cycle it on and off to see if the problem continues.
I suspect that IGN 1 and IGN 2 are somehow engaging at the same time in the ignition switch.
 
I don't know what kind of voltage regulator the instrument cluster uses in that year, but that's sounds like the problem. Those gauges won't last long with a solid 12v going to them. It's located on the back side of the cluster and should look like this.

Voltage Limiter
 
RustyRatRod said:
I don't know what kind of voltage regulator the instrument cluster uses in that year, but that's sounds like the problem. Those gauges won't last long with a solid 12v going to them. It's located on the back side of the cluster and should look like this.

Voltage Limiter
Click to expand...
I'm not strong with electrical at all.
I was worried about the gauges getting 12v, you confirmed my worries.
I was just outside shaking wires, everything went dead. I moved them around some more, then I'm back to where I started. So, I guess the problem is in that particular harness.
 
gunbunny said:
I'm not strong with electrical at all.
I was worried about the gauges getting 12v, you confirmed my worries.
I was just outside shaking wires, everything went dead. I moved them around some more, then I'm back to where I started. So, I guess the problem is in that particular harness.
Click to expand...
Check the firewall connector(s). They are notorious for giving trouble as these cars age. Disconnect them all and get a BRIGHT light and inspect the connections on both sides. Clean them GOOD and reassemble. But before you do all that, grab the connector(s) and wiggle them all around and see if that does anything.
 
RustyRatRod said:
Check the firewall connector(s). They are notorious for giving trouble as these cars age. Disconnect them all and get a BRIGHT light and inspect the connections on both sides. Clean them GOOD and reassemble. But before you do all that, grab the connector(s) and wiggle them all around and see if that does anything.
Click to expand...
That was the area I was jiggling around at. Tomorrow I'll give it a look, probably go get some electrical cleaner.
Wish me luck!
 
FYI. If your gauges are pegged to the right ( High/ full/ 60) there is a good chance that the gauges are or will be burnt out real quick. (speaking from experience, do your gauges sit well below the left end of the scale?)

gauges peg like that for 2 reasons

  1. IVR has failed and is not turning on and off making the pulsed DC needed by the gauges (likely, and effects all gauges at the same time)
  2. the sender wires for each gauge is shorted to ground (unlikely, that all 3 gauges separate sender wires got shorted at the same time)
As for brake light, do you mean the brake light on the dash or the brake lights at the back of the car.

If on the dash look for the switch and wire on the E brake handle for a short to ground.

If rear of car brake lights look at the brake switch that the brake pedal hits when it returns from pressing on the pedal. The switch is typically attached to an L bracket that has an adjusting bolt accessible from the passenger side of the steering column under the dash. ONLY bend the L bracket if it is not 90 deg bend and only to make it back into a 90 deg bend than adjust it by loosening the bolt and sliding it for or aft till the lights go out.
 
gunbunny said:
the brake light is on full time and the fuel gauge and temp gauge are pegged to the right side.
Click to expand...
reviewing the diagram and the one connector all three have in common which could ground is CI 10
1780657750246.png


That's the round connector on the back of the circuit board.
I'd check that cable bundle.

In my opinion less likely to be after the firewall connector because only 2 of the circuits go there.
1780658081663.png


The other goes to the body
1780658175275.png
 
Mattax said:
reviewing the diagram and the one connector all three have in common which could ground is CI 10
View attachment 1716551960

That's the round connector on the back of the circuit board.
I'd check that cable bundle.

In my opinion less likely to be after the firewall connector because only 2 of the circuits go there.
View attachment 1716551964

The other goes to the bo
Click to expand...
Okay, little update.
So I removed the bulkhead connectors. There was some corrosion especially at the location your circled. I had some battery cleaner, that, and wire brush cleaned up the corrosion. I put some dielectric grease on the terminals and same result.
A friend of mine came over, and suggested the voltage limiter is fried. A second friend said the same thing later in the evening.
I looked up under the dash, hoping I could replace it that way. I can see it, but there is a big bracket in the way.
So, how does one go about getting the speedo cable off of the speedo?
 
Dana67Dart said:
FYI. If your gauges are pegged to the right ( High/ full/ 60) there is a good chance that the gauges are or will be burnt out real quick. (speaking from experience, do your gauges sit well below the left end of the scale?)

gauges peg like that for 2 reasons

  1. IVR has failed and is not turning on and off making the pulsed DC needed by the gauges (likely, and effects all gauges at the same time)
  2. the sender wires for each gauge is shorted to ground (unlikely, that all 3 gauges separate sender wires got shorted at the same time)
As for brake light, do you mean the brake light on the dash or the brake lights at the back of the car.

If on the dash look for the switch and wire on the E brake handle for a short to ground.

If rear of car brake lights look at the brake switch that the brake pedal hits when it returns from pressing on the pedal. The switch is typically attached to an L bracket that has an adjusting bolt accessible from the passenger side of the steering column under the dash. ONLY bend the L bracket if it is not 90 deg bend and only to make it back into a 90 deg bend than adjust it by loosening the bolt and sliding it for or aft till the lights go out.
Click to expand...
Sorry, didn't see your post until now.
The brake light is the one on the dash.
The ammeter seems to be working, but the temp and the fuel gauge go full to the right.
Right now the consensuses is that the IVR has taken a dump.
Tomorrow, I'll tackle removing the instrument panel.
Any tips on getting the speedo cable off of the speedo?
 
A google of your cable shows it to be the same as mine, and if so, it is quite easy to do. Reach up behind the dash and feel for the plastic head of the speedo cable, push down on the tab and it should pull right off.
20240613_155108.jpg
 

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