Homemade gauge test tool, C-3826
Nice work! Can you show us how you use it?
The procedure is in all the factory shop manuals. All it does is substitute known resistance for the sender. So, say, if you think you have problems with the fuel gauge, you first make sure it has "solid" 12-14V to the instrument regulator, and that the regulator is probably OK.
Then you unhook the sender, and clip this from the sender wire to ground. There are 3 switch positions which give you the "empty", the "1/2" and the "full" mark on the gauge.
If that does not happen, you check the sender wire, and move the box up to the gauge cluster and retest, or check resistance and connections on the sender wire.
If that's OK, you are getting up to either a bad gauge limiter or the gauge itself.
What I've read indicates that all these vintage cars used the same gauge movements, so this box should work with fuel, temp, or optional oil gauges.
I plan, later, to build a 5V regulator into the box so I can also substitute the voltage limiter
