Scout 800 fuel guage question

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pineneedle

Member
I have been trying to bench test the fuel guage from my '67 800. Here is what I have done: the guage (now out of the truck) has two terminals on the back. I am presuming that one is power input and the other is power to the sending unit. I presume that the sending unit has to be grounded. So, I have a + lead to the gauge, then a wire from the gauge to the sending unit, then a ground wire from the unit to back to the battery. When the float is in the "tank full" position, the gauge shows "full." however, when the float is in the "empty" position, the gauge shows "half-full." both sending units behave in exactly the same way. Am I missing something or doing something wrong? Thanks in advance.

Pineneedle
 
Unlike the Scout 80 which uses the "constant voltage regulator" built into the engine termperature gauge pod, the Scout 800 instrument set uses an external "cvr" mounted on the rear of the instrument panel that powers all instruments (except speedometer and ammeter. This a power supply to converts b+ to an approximate "pulsed" 5vdc regulated signal.

Theory of operation and service of the instruments and the cvr are covered extensively in all ihc service manuals.

Attempting to power any of the instruments directly from b+ could render the meter movement toast in just a few seconds!

We've discussed this issue in many threads in the "electrical tech" sub-forum, here's a sample:

http://www.forums.IHPartsAmerica.com/electrical-tech/3283-pesky-crv.html

And:

http://www.forums.IHPartsAmerica.com/electrical-tech/2326-ohm-readings-fuel-sender.html

And:

http://www.forums.IHPartsAmerica.com/electrical-tech/3185-1975-loadstar-1700-fuel-gauge-problem.html

For starters, there are others also.

The cvr module looks like a large automotive circuit breaker, it's inside a steel cover/shell, about 1/2 the size of a horn relay. It's mounted adjacent to the rear of the fuel and coolant temperature gauges
 
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A quick way to test just the gauge is to use a couple of d cell batteries connected end to end as in a flash light for +3 volts. 3 volts is sufficient and safe to make a gauge move full scale without the risk of frying it.
 
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