69 coronet instrument gauge

[Dpbeats11]

I have a gauge like the one below. What reason would there be if oil warning light and brake warning light works, along with alternator gauge, but the temp and fuel gauge don’t work. Turn signal indicator lights on gauge work as well. Just seems like temp and fuel are having a problem.
Also, what would cause speedo gauge to bounce back and forth and never accurately display speed?

thanks

 

[Jerry Hall]

My guess is the speedometer needs rebuilt and the 5V regulator circuit is bad. If looks like a great candidate to have restored.

 

[Nacho-RT74]

Oil and brake lights use 12 volts and is a straight source from RUN circuit, while temp and gas are 5 volts regulated by the voltage limiter. If both guages are not working could be the voltage limiter... and if voltage limiter is gone, depending on how the voltage limiter went bad, the gauges could have said also bye to this life. I.e. if voltage limiter missed the ground, will send 12 volts to gauges and will burn the gauges.

Ammeter gauge ( I hate when is called alternator gauge, since is not am alternator gauge actually a batt gauge... but assembly plant made it wrong, not you. In any case, is an ammeter ) has its own life. Is an straight bridge between alternator and battery for positive pole.

Pilot lights ( turning and high beams ) got their own life too and same as cluster lighting, they only share the cluster ground common for every bulb except oil and brake.

Bouncing speedo, it could be from speedo cable dragging into the cover, or needle shaft bushing which also gets return spring begining to fail. OR also the input shaft needing lube. If a bushing failure and except if you are with skills and imagination able to fix it at home, this specific failure requires specific tooling what only rebuilding service shops will be able to make. But oiling/lubing could be made at home.

 

[Mackman]

My fuel and temperature gauge work sometimes for days, and then stop working for a bit. Then start working again. I assume voltage limiter?

 

[Nacho-RT74]

My fuel and temperature gauge work sometimes for days, and then stop working for a bit. Then start working again. I assume voltage limiter?

being both failing at the same time, yes, it points out to a VL failure OR the 12 volts power for it. Isn't this cluster with a PCB ? it could be also the pin for this source at the PCB being loosen.

I think the power for it is shared with the oil and brake lights, but if you are riding around, of course these lights will be off. Unless you try to activate the emergency brakes to light on the brakes light at cluster when gauges fail and IF the light comes on, then this 12 volts is arriving good to the cluster PCB

 

[Dpbeats11]

being both failing at the same time, yes, it points out to a VL failure OR the 12 volts power for it. Isn't this cluster with a PCB ? it could be also the pin for this source at the PCB being loosen.

I think the power for it is shared with the oil and brake lights, but if you are riding around, of course these lights will be off. Unless you try to activate the emergency brakes to light on the brakes light at cluster when gauges fail and IF the light comes on, then this 12 volts is arriving good to the cluster PCB

Thank you both for that advice. I will start with VL and go from there.

 

[Dpbeats11]

Thank you both for that advice. I will start with VL and go from there.

installed new VL. Still no luck. Starting to think issue is in engine compartment. Wiring does not hold up. Jiggled wires while running to see if temp gauge would read and it shut off. Maybe related to ignition. It’ll crank but won’t fire now. Now I have a non running car. Fml

Side note - What is this connected with the VL?

What is best place to get engine wiring and connectors in bulk?

 

[Nacho-RT74]

As mentioned, if the VL got damaged, THERE IS A CHANCE the gauges could get burn too, depending of the nature of the damage in the VL

You can try to test the gauges easy... with a couple of 1.5v batts in series, feed both studs at gauges on back of cluster. Needle must move up to around 2/3 of the reading.

You can try any other source... usb one, which feeds 5 volts. Will read full on gauges.

You can even try with a squared 9 volts batt, but WITH CAREFULL, because can get burnt the gauges. Just a couple of seconds will be enough.

The voltage limiter gets a capacitor just for filtering noises into the radio.

At this moment M&H is the best wiring supplier fo our harnesses, originally being sold in exclusive through Year One, now several other also offer those. Of course is better try to wait to te 30% discount season.

But I bet you won't need to get a full harness replacement. Usually my opinion is, just the engine and transmission harness use to need a full replacement due the heat and oil the get allong the years, but the rest of car harnesses just need a check and mantenience job. While an underdash harness price is around $600, what you think it needs a full replacement can be fixed ( if something is really wrong on them ) with $20-100 investment.

and patiente