1955 speedometer & fuel gauge not working

[c Ed]

I just purchased a 1955 for my 83 year old Dad to drive and enjoy. The speedometer & fuel gauge aren’t working. Planning to tear into it and see what I can find. Any advice for a new owner?

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[dmsfrr]

At the risk of being overly cynical...
If you want him to drive it while he still can and those are the biggest problems it has, ignore the speedometer and top off the fuel tank every 100 miles.
It may be something simple like a disconnected speedometer cable and a broken wire to the fuel tank sensor.
But if you 'tear into it' much more than that, you may find it sitting in the garage waiting for parts more often than being driven and enjoyed.

 

[c Ed]

Thanks, yes these are biggest issues. Run & drives good. Will need to be restored at some point but not while he can enjoy it.

 

[Ward 57]

At the risk of being overly cynical...
If you want him to drive it while he still can and those are the biggest problems it has, ignore the speedometer and top off the fuel tank every 100 miles.
It may be something simple like a disconnected speedometer cable and a broken wire to the fuel tank sensor.
But if you 'tear into it' much more than that, you may find it sitting in the garage waiting for parts more often than being driven and enjoyed.

It has taken almost two summers for that exact reason to get my car road worthy. Now this year I can concentrate on the cosmetics.

 

[doug7740]

I just purchased a 1955 for my 83 year old Dad to drive and enjoy. The speedometer & fuel gauge aren’t working. Planning to tear into it and see what I can find. Any advice for a new owner?

My advice is repair the speedometer and fuel gauge before giving it to your dad. Nothing takes the enjoyment out of driving a classic car than looking at a speedometer that reads zero all the time or a fuel gauge that remains on empty. I would always be wondering how fast I was going and if I had enough fuel to get home. At the very least check to see if the speedometer cable is disconnected or if the yellow wire that runs from the fuel tank sending unit to the fuel gauge is disconnected or broken.

Attached is an article I wrote on how to diagnose an inoperative or noisy speedometer. If after going through the article your speedometer still doesn’t work, let me know and I’ll go through the steps on how to remove and repair your speedometer.

As far as the fuel gauge goes, if you disconnect and ground the yellow wire at the sending unit and the gauge reads full, the problem is with the sending unit in the fuel tank. If the fuel gauge doesn’t read full after you disconnect and ground the yellow wire at the sending unit, the problem could be with the wiring or the gauge itself. The fuel gauge is a very simple circuit, so start by disconnecting and grounding the yellow wire and let me know what happens.

Making these repairs could be a great father and son project. Remember, half the fun of owning a classic car is doing the repairs yourself.

doug7740
1955 Thunderbird Blue

 

[c Ed]

My advice is repair the speedometer and fuel gauge before giving it to your dad. Nothing takes the enjoyment out of driving a classic car than looking at a speedometer that reads zero all the time or a fuel gauge that remains on empty. I would always be wondering how fast I was going and if I had enough fuel to get home. At the very least check to see if the speedometer cable is disconnected or if the yellow wire that runs from the fuel tank sending unit to the fuel gauge is disconnected or broken.

Attached is an article I wrote on how to diagnose an inoperative or noisy speedometer. If after going through the article your speedometer still doesn’t work, let me know and I’ll go through the steps on how to remove and repair your speedometer.

As far as the fuel gauge goes, if you disconnect and ground the yellow wire at the sending unit and the gauge reads full, the problem is with the sending unit in the fuel tank. If the fuel gauge doesn’t read full after you disconnect and ground the yellow wire at the sending unit, the problem could be with the wiring or the gauge itself. The fuel gauge is a very simple circuit, so start by disconnecting and grounding the yellow wire and let me know what happens.

Making these repairs could be a great father and son project. Remember, half the fun of owning a classic car is doing the repairs yourself.
View attachment 26798
doug7740
1955 Thunderbird Blue

this was very helpful! I found the speedometer cable was disconnected. I connected it and it was noisy. I’m assuming that is why it was disconnected. I’ll follow the advice in the article you wrote on lubricating the cable and then reinstall. Hopefully that will solve the issue. Going to look at the yellow wire on the sending uniyt tomorrow. I really appreciate the assistance. Dad is going to love cruising around in this car! Thanks!

 

[doug7740]

Before re-connecting the cable housing to the back of the speedometer head, don't forget to put a few drops of oil on the wick through the hole in the speedometer head. Looking at the speedometer from the back, the wick hole is at the top and can not be seen from underneath. I used a bottle like the one below to periodically lubricate the speedometer on my Thunderbird.



Since your speedometer is very noisy, you might have to apply the oil a few times before you see any improvement.

doug7740
1955 Thunderbird Blue

 

[Ward 57]

Before re-connecting the cable housing to the back of the speedometer head, don't forget to put a few drops of oil on the wick through the hole in the speedometer head. Looking at the speedometer from the back, the wick hole is at the top and can not be seen from underneath. I used a bottle like the one below to periodically lubricate the speedometer on my Thunderbird.

View attachment 26800

Since your speedometer is very noisy, you might have to apply the oil a few times before you see any improvement.

doug7740
1955 Thunderbird Blue

Sewing machine is packaged the same way and probably just as good and easier to find.

 

[Critterpainer]

This may or may not be relevant to the fuel gauge but is the Bird 6V positive ground as original or has it been converted to 12V negative ground?

 

[doug7740]

The fuel and temp gauges will work on 6 or 12 V and are not polarity sensitive.

doug7740
1955Thunderbird Blue

 

[c Ed]

it has a 12V battery & alternator, but I haven’t tracked it down to see if it is stepped down somewhere under the dash.

 

[doug7740]

When your car was converted to 12 volt negative ground the same gauges were used without stepping down the voltage. The fuel and temp gauges will work on 6 or 12 V and are not polarity sensitive.

doug7740
1955 Thunderbird Blue

 

[c Ed]

This is very helpful, thanks for sharing!

 

[dmsfrr]

When your car was converted to 12 volt negative ground the same gauges were used without stepping down the voltage. The fuel and temp gauges will work on 6 or 12 V and are not polarity sensitive.

For those who are curious, here's why....
The '55 King-Seeley gauges work on current flow and heat, not variable resistance or a polarity sensitive gauge.
Bi-metal on/off switch contacts in the sensor control the averaged amount of electrical flow thru a set of heating coils that in turn affects movement of the gauge needle.
The sensor and circuit are effectively self regulating, as long as the sensor and gauge are year matched.
'56 was the first year of 12v and the electrical design specs of the parts were changed.
For '57 the sensor was changed again, to a variable resistor.