Note : these tests are made with sending units removed from car


OIL PRESSURE:  I use an air compressor and blow air through the fitting at rear of gauge. Be careful ! Don't use full pressure of the compressor !

No pressure ( 0 psi)

Reading : 0 or "low"
Pressure = 3,2 bars or 50 PSI Reading:  1/2 of scale
Pressure = 6 bars or 90 PSI Reading "high"

  the dash gauge is wired to :

  • + 12,5 V DC supply
  • to some solid resistors (other end of resistor to ground) : R in the table below
  • ground
R = 240 to 270 ohms Reading : 0 or "cold"
R = 45 to 51 ohms Reading:  1/2 of scale
R = 12 to 15 ohms Reading "hot"

Below you'll see the temperatures readings on my  '57 Imp. gauges, see table to convert in F. Remember that normal T is between 170 and 190 F (thermostat opens at 160 or 180, depending if car is non A/C or A/C). So in normal conditions the needle must not go after the middle mark.
i test the sending unit in a boiling jar with digital thermometer. The unit was wiring to the dash gauge.

temp in C 30 to 40 C 60C 75C 88C 98C
temp in F 86F to 104F 140F 167F 190F 208F


GAZOLINE : the dash gauge is wired to:

  • + 12.5 V DC supply
  • to the tank unit (removed from tank)
  • ground

                                The tank unit is wired to:

  • dash gauge
  • ground

You move the arm to different positions according to the reading of the gauge ;  at each position you shut off the supply and measure the resistance between tank gauge pin and ground:

R = 170 ohms Reading : "empty"
R = 78 ohms Reading:  1/2 of scale
R = 26 ohms Reading "full"

Note: i 've not tested the amperemeter gauge, i haven't any power source ..

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