70 Road Runner Electrical Issue

[mikelin44]

Went to a car show the other night and when I was ready to leave and flipped the headlight switch on, the headlights and taillights lit, the tach (just a tach) was fully lit, only the speedometer’s left side was lit, none of the gauges were lit, the gas gauge shut off and went to E and the other gauges stopped working altogether.
Never had this problem before, any ideas what could have caused this?

 

[pnora]

Cluster losing the ground on that circuit board.

 

[mikelin44]

Cluster losing the ground on that circuit board.

Thanks, I ordered a new circuit board and of course the supply chain has it delayed for however long

 

[pnora]

Thanks, I ordered a new circuit board and of course the supply chain has it delayed for however long

Why? You might just repair the ground.

 

[devinism]

If I remember correctly...Your circuit board grounds through the dash cluster. Make sure your cluster is tight. It wouldn't hurt to run an additional ground strap to it.

 

[Rusty 72]

Wiggle the ignition switch? The headlights should come on without any ignition power, ie: why their working. I've had bad ignition switches in the past that acted like this.

 

[steve817]

Went to a car show the other night and when I was ready to leave and flipped the headlight switch on, the headlights and taillights lit, the tach (just a tach) was fully lit, only the speedometer’s left side was lit, none of the gauges were lit, the gas gauge shut off and went to E and the other gauges stopped working altogether.
Never had this problem before, any ideas what could have caused this?

Have you had your 50 year old switches, gauges or entire gauge cluster restored? Your original circuit board would be best to restore.
1: If your lower left tach bulb was illuminated and not the other two (separate from the 3 circuit board bulbs), it’s either 2 bad bulbs, ground issue at individual bulb sockets or no power going to both unlit bulbs. Has nothing to do with circuit board.
2: “none of the gauges were lit”
I’m assuming you are referring to the 3 circuit board bulbs for the small gauges?
Those bulbs get their ground from the three screws that attach the board to the cluster housing and ultimately the cluster housing to the dash frame and on to the car body. If your lower left tach looking gut was working, that tells me that your cluster housing to dash frame ground is ok. I would check the power that controlled ALL of the orange wires dash dimming bulbs which comes from the dash dimmer switch. Now if your dash dimmer switch is original and never been restored, that is a problem. The potting compound that holds the resistance wire in the ceramic holder is brittle and WILL fail,
(ask Devinism…he knows). Lots of people say “I got a new dimmer switch” or “the dimmer switch looks good”. I am here to say that if you bought a new repop one, that’s the problem or, if your original switch has not been restored, that is a problem now or WILL be a problem with many electrical problems. Now, for the gauges not working. You said “gas gauge went to E and the other gauges not working all together”. Each gauge (fuel, temp, oil) gets a different ohm reading from a different wires. If ALL three gauges went bad at once, Its more likely a power problem. The culprit could be 12 volts NOT getting to the circuit board pin, voltage limiter not supplying the 5 volts to each gauge(if your old voltage limiter fails, it will send 12 volts to the 3 small gauges and WILL fry them. Let Devinism know if you need your switches restored and if you need your complete cluster restored, there’s the big companies like Shannon at Redline Gauges or you can contact me if you have questions or want your gauge cluster restored. Check out my work here on “For B bodies Only”. Please let us know what you find. Also, if you do decide to restore your cluster, save some money and send that “new” circuit board back as the original can be restored to better then new. It’s part of my restoration process. Thanks, Steve

 

[pnora]

Have you had your 50 year old switches, gauges or entire gauge cluster restored? Your original circuit board would be best to restore.
1: If your lower left tach bulb was illuminated and not the other two (separate from the 3 circuit board bulbs), it’s either 2 bad bulbs, ground issue at individual bulb sockets or no power going to both unlit bulbs. Has nothing to do with circuit board.
2: “none of the gauges were lit”
I’m assuming you are referring to the 3 circuit board bulbs for the small gauges?
Those bulbs get their ground from the three screws that attach the board to the cluster housing and ultimately the cluster housing to the dash frame and on to the car body. If your lower left tach looking gut was working, that tells me that your cluster housing to dash frame ground is ok. I would check the power that controlled ALL of the orange wires dash dimming bulbs which comes from the dash dimmer switch. Now if your dash dimmer switch is original and never been restored, that is a problem. The potting compound that holds the resistance wire in the ceramic holder is brittle and WILL fail,
(ask Devinism…he knows). Lots of people say “I got a new dimmer switch” or “the dimmer switch looks good”. I am here to say that if you bought a new repop one, that’s the problem or, if your original switch has not been restored, that is a problem now or WILL be a problem with many electrical problems. Now, for the gauges not working. You said “gas gauge went to E and the other gauges not working all together”. Each gauge (fuel, temp, oil) gets a different ohm reading from a different wires. If ALL three gauges went bad at once, Its more likely a power problem. The culprit could be 12 volts NOT getting to the circuit board pin, voltage limiter not supplying the 5 volts to each gauge(if your old voltage limiter fails, it will send 12 volts to the 3 small gauges and WILL fry them. Let Devinism know if you need your switches restored and if you need your complete cluster restored, there’s the big companies like Shannon at Redline Gauges or you can contact me if you have questions or want your gauge cluster restored. Check out my work here on “For B bodies Only”. Please let us know what you find. Also, if you do decide to restore your cluster, save some money and send that “new” circuit board back as the original can be restored to better then new. It’s part of my restoration process. Thanks, Steve

Please read his starting post. His issues have everything to do with the right circuit board. The right side of the cluster is on a circuit board. All the others are on individual wires with bulb sockets. With his tachometer and left dash lights working that eliminates the headlight switch and the dimming switch. [period] His problem is twofold right illumination and no gauges. Both need a ground. This can easily be diagnosed.

 

[steve817]

Wiggle the ignition switch? The headlights should come on without any ignition power, ie: why their working. I've had bad ignition switches in the past that acted like this.

Sounds like the headlights and taillights did work.

Please read his starting post. His issues have everything to do with the right circuit board. The right side of the cluster is on a circuit board. All the others are on individual wires with bulb sockets. With his tachometer and left dash lights working that eliminates the headlight switch and the dimming switch. [period] His problem is twofold right illumination and no gauges. Both need a ground. This can easily be diagnosed.

glad you are on it and can help him out. I can’t wait to hear what the problem is.

 

[mikelin44]

An update to the issue, I replaced the temperature and oil pressure gauges last year. In addition, I replaced the voltage limiter also. Today, as soon as the dash lights would come on, that causes the gauges to stop working. Before the dash was reinstalled, everything was tightened down.

 

[pnora]

An update to the issue, I replaced the temperature and oil pressure gauges last year. In addition, I replaced the voltage limiter also. Today, as soon as the dash lights would come on, that causes the gauges to stop working. Before the dash was reinstalled, everything was tightened down.

You are losing the ground.

 

[devinism]

For what it's worth.... I have heard of the replacement voltage limiters going bad. The symptoms seem familiar.

 

[pnora]

For what it's worth.... I have heard of the replacement voltage limiters going bad. The symptoms seem familiar.

That does not make sense. His gauges are working but loses them when the dash lights are turned on. The lights are taking the ground away from the limiter. He needs to verift a ground at the board. My bets if he installed a auxiliary ground to the board at this screw the problem would be fixed..

 

[devinism]

That does not make sense. His gauges are working but loses them when the dash lights are turned on. The lights are taking the ground away from the limiter. He needs to verift a ground at the board. My bets if he installed a auxiliary ground to the board at this screw the problem would be fixed..

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If I remember correctly...Your circuit board grounds through the dash cluster. Make sure your cluster is tight. It wouldn't hurt to run an additional ground strap to it.

From my earlier post.
And you are correct... It does not make sense, but I have had 2 different switch customers get back to me with what they found (after HOURS of chasing). Swapped in another VL and boom....problem solved.

 

[pnora]

From my earlier post.
And you are correct... It does not make sense, but I have had 2 different switch customers get back to me with what they found (after HOURS of chasing). Swapped in another VL and boom....problem solved.

Reason I am sticking with the ground is because he is also losing the dash lights on that side. With the gauges and the dash lights acting up at the same time its hard to believe its the limiter. I would have it diagnosed in a couple minutes.