[VetteVet]

You are a lucky guy because the wire on the prop valve is a ground wire and the light comes on when this wire grounds due to low brake fluid or pedal pressure letting the prop switch complete to ground. You can test the light by grounding this wire and turning the key on.

Normally the light will light up when the key is turned to the start position and go off when released unless the wire to the prop valve is grounded. There should be a ground wire going to the key switch for this purpose. I think the temperature light works the same way. Check and see if you have a black wire going to the key switch. If not then the key switch may ground internally for those two wires. They are light brown (brake ) and dark green (temp).