[dscott]

The amber light stays on until the engine is running. The voltage from the regulator is where the signal comes from. Once the proper voltage is reached the light goes out. The brake warning light signal does come from the prop valve and is for low pressure. You can take the prop valve off and reset the plunger, you will need to take the prop apart to do this, or get a used one at a salvage yard. It's from a 1974 to 1978 Mustang II. We don't use them anymore. We have an adjustable valve that goes in the rear brake line only. The front is now a direct hookup. We no longer use the red light since there is no hookup for a light on the adjustable prop.
Don