When I check the voltage of my cigarette lighter in the car. The needle goes backwards. In other cars the needle registers the full 12 volts. It looks to me as though the wiring system is the wrong way round, what do you think and if I am right what is the cause.
how are testing it
Well the cig lighter isn't a complex electronic item,
it's not polarity sensitive so could be it's wired wrong,
it should work wired up either way.
Other electrics not so much.
If the battery polarity is reversed it would most likely blow the ECU so the car wouldn't run at all.
So pull the lighter out and check the wiring.