Slow indication when cold...

[Hawklover]

Could outside temps of around 45 degrees cause the guages on my Avanti to be slow reacting?

I noticed that the tach and fuel gauge did not register for almost two minutes, this malady never happened when the outside temps were in the 60's and above.

[GrumpyOne]

Yes, temperatures affect anything electronic/electric...

In the case of the tach, I would suspect dying capacitors in the sending unit or any other location where capacitors are part of the circuit boards. Even discrete capacitors will die when hardly used over long lengths of time.

OTOH, the fuel gauge system is much simpler where most often the variable resistor in the sending unit wears physically over time is the culprit.

But as an aside, since both items issues developed simultaneously it could be an uneven supply of power from the source of regulated voltage...

[Hawklover]

Interesting things to consider.....the car does sit unused for 9 months of the year. I replaced the sending unit maybe 5 years ago, and it is the third sender the car has seen since new. After the car warmed up and driven for a few hours the aforementioned did not repeat itself. When you say the sending unit, you mean the float in the gas tank, correct? When you say regulated supply, you mean the voltage regulator? Next week I will most likely be attendeing a large auto show/flea market.....I shall see if this situation repeats itself. I do not think this is a situation of loose connection(s) or dirty ones.

Yes, temperatures affect anything electronic/electric...

In the case of the tach, I would suspect dying capacitors in the sending unit or any other location where capacitors are part of the circuit boards. Even discrete capacitors will die when hardly used over long lengths of time.

OTOH, the fuel gauge system is much simpler where most often the variable resistor in the sending unit wears physically over time is the culprit.

But as an aside, since both items issues developed simultaneously it could be an uneven supply of power from the source of regulated voltage...

[gordr]

There isn't a source of regulated voltage. The gauges run off straight 12 volts from the ignition switch. Like other Studebakers, they are Stewart Warner "thermo" gauges. The pointer is attached to a pair of bimetal strips that bend when heated, deflecting the pointer. Each of those strip has a heating element wound around it. Both heating elements get 12 volts from the (+) stud on the gauge. One gets its ground from the sending unit, and the other is grounded to the gauge case, which must be grounded to the car body (which is non-trivial with a fiberglass dash!). The sending unit (be it temp or fuel) lowers its resistance as the quantity being measured increases, sending more current through that little heating element, bending the bimetal more, and deflecting the pointer upscale. The other bimetal acts to oppose the first one, and it varies its bend with voltage variations only. The idea being that the effect of voltage variations is canceled out by having one bimetal shift the pointer up with increased voltage, while the other shifts it down, meaning no net pointer movement from voltage variations.

TLDR? The gauge is its own voltage regulator.

Needless to say, the colder the ambient temperature, the longer it takes for the bimetals to be heated to the point that they begin to move the pointer.

[Hawklover]

Thank you Gordon....you know when the car was almost new in 1966 I drove it all during the winter months of New York...never had an issue.....but then the car was only two years old, maybe the old gal is full of arthritis:-) What is TLDR? Also why would the tach be effected, same reason as the fuel guage?

There isn't a source of regulated voltage. The gauges run off straight 12 volts from the ignition switch. Like other Studebakers, they are Stewart Warner "thermo" gauges. The pointer is attached to a pair of bimetal strips that bend when heated, deflecting the pointer. Each of those strip has a heating element wound around it. Both heating elements get 12 volts from the (+) stud on the gauge. One gets its ground from the sending unit, and the other is grounded to the gauge case, which must be grounded to the car body (which is non-trivial with a fiberglass dash!). The sending unit (be it temp or fuel) lowers its resistance as the quantity being measured increases, sending more current through that little heating element, bending the bimetal more, and deflecting the pointer upscale. The other bimetal acts to oppose the first one, and it varies its bend with voltage variations only. The idea being that the effect of voltage variations is canceled out by having one bimetal shift the pointer up with increased voltage, while the other shifts it down, meaning no net pointer movement from voltage variations.

TLDR? The gauge is its own voltage regulator.

Needless to say, the colder the ambient temperature, the longer it takes for the bimetals to be heated to the point that they begin to move the pointer.

[gordr]

TLDR = too long, didn't read.

Tach might be slow because of gummy oil on pointer shaft. I seem to remember my old Avanti doing that, too.

[GrumpyOne]

There isn't a source of regulated voltage. The gauges run off straight 12 volts from the ignition switch. Like other Studebakers, they are Stewart Warner "thermo" gauges. The pointer is attached to a pair of bimetal strips that bend when heated, deflecting the pointer. Each of those strip has a heating element wound around it. Both heating elements get 12 volts from the (+) stud on the gauge. One gets its ground from the sending unit, and the other is grounded to the gauge case, which must be grounded to the car body (which is non-trivial with a fiberglass dash!). The sending unit (be it temp or fuel) lowers its resistance as the quantity being measured increases, sending more current through that little heating element, bending the bimetal more, and deflecting the pointer upscale. The other bimetal acts to oppose the first one, and it varies its bend with voltage variations only. The idea being that the effect of voltage variations is canceled out by having one bimetal shift the pointer up with increased voltage, while the other shifts it down, meaning no net pointer movement from voltage variations.

TLDR? The gauge is its own voltage regulator.

Needless to say, the colder the ambient temperature, the longer it takes for the bimetals to be heated to the point that they begin to move the pointer.

I'm going to have to take issue with "regulated voltage" which is the task of the regulator.

For example, if one simply turns the ignition switch to the "run" position but the car has not started, gauge reading will read lower hence if a regulator has gone out of its factory tolerance settings, gauges may indeed be slow to respond. Very often I would get a different gauge reading in a variety of cars that gave different values depending on whether the head lights were on or off.

If the value of the incoming voltage is out of tolerance to the gauges, the readings are likely to be less accurate especially since our cars are analog.

Another example is my old T-cab that had a GM internal regulator which like to turn on about five minutes after the truck was started. Readings were low before and normal after...

[gordr]

Let us just say that the design of the gauges makes them "voltage compensated", then. If the system voltage is within the normal operating range, they do OK.

[Hawklover]

UPDATE!!!!
Its not the gauges at all:-(...........the new ignition switch is stiff and does not return fully......the moment I nodged the key a tiny bit the tach, gas gauge and temp gauge came on line.

[Jessie J.]

There were complaints to Studebaker Corp. about their slow to read gauges in the early '60s. 1964's television adds make a point out of mentioning their new 'quick' reading gauges, ...which if my own '64 Daytona's are any example, were still slower responding than most.