Re: Hydraulic stop light switch

Posted by HH56 On 2019/6/25 12:16:52

If the back seat courtesy light works and the car is stock, the trunk light should be getting power. The trunk light is powered via a splice in the same wire feeding the rear courtesy light and originates at the 30amp always powered breaker. That breaker also feeds the brake lights. It is very possible the steel ball inside the trunk light assy that rolls and connects power to the bulb when the lid opens has rusted or corroded and the switch is not making contact. A fairly common problem and there are a few posts on the forum where people have been able to restore contact by removing and shaking the lamp assy vigorously to kind of beat or wear off the rust or, on the older mercury switches, the coating that develops on the contacts. Other times the shake method has not been successful and it requires a new and different switch. I had to go that new switch route on my 47.

There is a mistake in the 54 Packard wiring diagram on the fuel sender wire. In actuality there should be no connection between the fuel sender wire and any lights. Fuel sender is an orange wire which has one inline connector that usually is positioned just after the short length of wire from the tank unit enters thru the grommeted hole in the rear of trunk floor. Occasionally the connector is underneath but other than the connector the wire goes directly and only from the sender to a terminal on the gas gauge. In the 54 diagram they indicate a splice going to a senior back up light on that wire instead of where it really is on the green wire next to it that takes care of back up lamps.

Best I can suggest on the gauges is check the instrument voltage regulator. It is possible that item has failed which would affect both gauges. Since the turn signals work the breaker feeding the regulator should be OK since turn signals also get power from the same breaker. If you have a voltage at both terminals on the regulator there should also be power at both gauges. If nothing at the terminal toward the side then the regulator is bad. If there is power, ground the wire out at the temp sender. If the gauge moves the sender is the problem, if nothing happens then the wire or the gauge. The fuel gauge can be tested the same way by disconnecting the inline connector in the trunk and temporarily grounding the wire as someone watches the gauge. If it moves the sender is the problem, if not then wire or gauge. Don't leave the wires grounded longer than it takes to verify that the gauges move.