57/58 guages question (asking for Old Gasser)

[mustang6984]

Old Gasser cannot get on the forum to post for some reason, so he asked Alvin to post this, and Alvin passed it on to me. So:

************************************************************************
Alvin do you know why Ford installed 6 volts gauges in the 57 & 58 dash cluster & then installed a 12 volt constant voltage regulator to accommodate the 6 volt gauges.

When in 1956 the Fords & Mercury's had 12 volt gauges so why did Ford go back to the 6 volt gauges as they had in the 1955 Fords?

When a person is checking the Ohm readings in the dash cluster gauges of the 57/58 Fords & the constant voltage regulator happens to be burnt out & your testing with 12 volts what happens is you end up putting 12 volts into the gauges which in-turns  burns the both gauges out.
Hence the Question why did Ford do this gauge change in the 57/58 cluster?
Alvin if you don't know I'm wondering if in your words you can post this on the 57 Board & see if we get an answer?

I haven't the answer...so if one of you do...please share. Thanks. Hugh.

[1930artdeco]

It thought it had something to do with burning the gauges out over time?

[hiball3985]

I'd like to know why too. But the CV regulator for gauges went on way past 59. My 60 F100 and 66 Mustang has one as does my 66 F250, I think they went into the early 70's?

[thomasso]

Its a constant voltage regular and prevents voltage spikes which will damage gauges.  Its not a resistor.  The gauges are 12 V.

[oldave57]

The following is taken directly from my 1957 Ford shop manual:

Fuel Gauge and Temperature Gauge
The voltage regulator used with the fuel and temperature gauges maintains an average value of 5.0 volts at the gauge terminals.  The regular is temperature compensated for all expected ambient temperatures.

The gauge circuit then passes through the sending units which apply restriction to reduce gauge voltage depending on either temperature or fuel level.  If you ground the circuit after the gauge, the fuel gauge will read full and the temp gauge read hot. 

The manual further states that you can test the gauge by applying 3 volts (2 flashlight batteries in series) and then grounding the sending unit circuit.  3 volts should place the gauges at around mid range.

There is no mention of the reason for reducing the voltage to the gauges.

[thomasso]

Evidently I was wrong. Don't know everything after all.

[mustang6984]

Evidently I was wrong. Don't know everything after all.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

uh oh...I was sorta counting on you knowing everything! GULP!     

Hey...I know nothing...so all's good!

[cokefirst]

The 1957 and later gauges work on a completely different principal than the earlier gauges.  They did not use a resistance type sending unit but a more complicated coil heating system.  It worked well and was used from the first gauges in the 30's through 1956.  GM, Chrysler and most other US manufactures use the resistance type senders much earlier than Ford  Ford was the only manufacturer that I know of that used the dash gauge constant voltage regulator. 

[oldave57]

The 1957 Ford shop manual describes the circuit very well for both the fuel and temperature gauges.  The gauges do have a heating coil that responds to voltage variations depending on the resistance from the sending units that are downstream from the gauge, causing a voltage change with change in either temperature or fuel level.  If you ground either the temperature wire at the block or the fuel gauge wire at the fuel tank, both gauges will go to full scale (hot or full) because the resistance of the sending unit has been eliminated.  The pictures below show the circuits in good detail.