Not a cry for help just an observation from a professional mechanic/electrician. When testing for supply voltage to lamps etc.

most people use a digital multimeter, these can be very misleading

under certain circumstances as they impose only a minute load to the circuit under test.My preference is to use a 12v test lamp for this.

To see this in action, attach say, a 500 ohm resistor to the positive battery terminal

and use a digital meter to measure between the other end of the resistor and the negative battery terminal result - battery voltage.

Now substitute a 12v 5 watt bulb result = no light!

The reason is that the bulb draws a current through the resistor causing

a voltage drop, the digital meter does not, and that resistor is just what you get from a poor wiring connection!

WARNING do not use test lamp on ELECTRONIC components they dont like high currents.