84,
Since I presume you are talking about an '84 Camaro that is NOT a Berlinetta, you should have analog gauges, not a digital gauge pod. In either case, the instruments receive an analog voltage signal from the corresponding sensors. The voltage for most instruments varies between 0-12VDC. The instrument will display a relative reading based on the input voltage. Digital instruments operate the same way, but the instrument cluster uses A-D converters in the electronics package to convert the analog voltage to a digital "count" to be displayed. The scaling of these converters is fixed by the firmware, and cannot be adjusted. Most of these dashes use a 0-5VDC source.
All gauges rely on correct analog voltage from the sensors, so electrical connections, including grounds, are very important. The analog oil pressure gauge, coolant temperature gauge, voltmeter, and fuel level gauge use a normal 0-12VDC supply for the instruments. The speedometer uses digital pulses generated by the VSS and actually counts the pulses to display speed. The tachometer uses pulses generated by the HEI module and averages those counts to display engine RPM.
The ECM supplies the 5VDC supply for some of the ECM sensors, so connections there are crucial as well. These sensors don't normally get used for the instruments, but any discrepancies between the ECM readings and the instrument indications could be due to a poor 5VDC supply connection.
For the purposed of testing, you should be able to vary a 0-12 VDC input supply to each of the analog instruments and expect a relatively accurate display. Remember that the coolant temperature and fuel level indicators are not truly linear, so a 6VDC signal may not display half-scale. Examine the markings on the temperature gauge and you'll see the non-linear scaling.
__________________ Later,
Vader
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