Back up light fuse shorts constantly

SAGCARPRO

MEMBER
2000 PLYMOUTH NEON
2.0L
4 CYL
2WD
AUTOMATIC
250,000 MILES

I have a 2000 Plymouth Neon. It has been running fine until about two weeks ago. About two weeks ago it stopped on my wife suddenly when she stopped at a friend's house. It started back up later. It stopped on her again and would not start up so I went and/ based on internet reports of similar situations, saw corroded battery cables and changed them with a temporary fix and it started fine. I also found 3 blown fuses and replaced them with resetting type fuses that would reset if blown. The 20 amp fuse to the heater blower motor is okay. The next day she told me the fuses I had put in to replace the burnt ones which were the circuit breaker type of fuses were clicking and the tiny lights on the door and window switches were turning on and off. I drove it to work and it ran fine until the last 35 miles is started clicking on me and after I stopped at a stop light and died on me it started up easy but any attempt at acceleration would kill the engine. Eventually I slowly accelerated and got out of there and returned home. Accelerating in a reverse gear would NOT cause it to shut off. For a while it kept on starting then dying upon acceleration with the fuses audibly clicking as they were breaking the circuit.

But now just turning on the ignition key
causes the fuse number 7 to blow each time.
And a if I use a circuit breaker fuse it constantly clicks on and off.

I checked the relays under the hood in the fuse box there and using the relay for the horn that worked properly replaced it with the one in the position for the automatic shutoff relay and the fuses still would short and the asr fuse let the horn work properly so I doubt if the relay is the problem.

1 Reply

CARADIODOC

MECHANIC
33,741 POSTS

There's a better alternative to those circuit breakers. A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

Fuse 7 feeds a number of systems with switches in the front doors. I'd start by opening and closing the driver's door. If the test light flickers, check for broken or frayed wires between the door hinges.

When the engine originally didn't start, what was the symptom? Did the starter crank the engine? Did the dash lights work? If everything was totally dead, follow the smaller positive battery wire to the under-hood fuse box and be sure that connection is clean and tight. That's a common cause on all car brands for an intermittently totally-dead electrical system.

Be aware you're going to have a hard starting / stalling problem since the battery was disconnected. The Engine Computer lost its memory and will have to relearn "minimum throttle" before it will know when it has to be in control of idle speed. You also won't get the nice "idle flare-up" to 1500 rpm at start-up and the engine will tend to stall at stop signs. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.