Electrical question on old car

Dab45Dab45 Member Posts: 2
edited April 2021 in Mercury
Hello. I hope someone in the know would be kind enough to help me. I have a 1978 Mercury Grand marquis with the 460 v8. Whenever I plug anything into the cigarette lighter, be a charger or cigarette lighter, the fuse for the cigarette lighter blows. Here is what I've done so far, with no success. Checked connections to the lighter plug, checked continuity at the fuse (failed), checked for voltage at the fuse (it showed 12.5 volts), replaced the whole cigarette lighter plug assembly. Still blowing fuses. I noticed when I wiggled the wires to the cigarette lighter, the key buzzer which is intermittently not working, started to buzz. Does this mean there is a problem with the wiring that I am not detecting or a bad ground somewhere? Any information would be appreciated. Thanks!


  • MichaellMichaell ColoradoModerator Posts: 209,776
    @tjc78 - I think this one may be up your alley...

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  • Dab45Dab45 Member Posts: 2
    edited April 2021
    This is what I have done since my last post. Hopefully someone can help me. I decided to disconnect the wiring to the lighter and rewire it. I disconnected the hot wire to the lighter and the ground wire. I put electrical tape over them. Then I put a wire, with an inline fuse, to the accessory feed on the fuse box for power. Then i created a new ground wire and grounded it. Any splicing done with butt connectors All seemingly very clean. Now the lighter works great. Unfortunately, I'm noticing that the door ajar buzzer is not working at all. It used to work intermittently. Also, I notice a funny one second buzz when the interior lights come when the door is ajar. This also used to happen intermittently,. My question now is: should disconnecting the lighter like I did cause other electrical systems, like the warning buzzer, to malfunction? Are other circuits somehow grounded through the cigarette lighter? Should it have any affect at all. Thanks!!
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