Battery Runs Down
Question: I have an '84 pace car. I used to drive it daily. For the past six months I have driven it very little. I'm now having a problem with the battery running down if I don't start it up every day and let it run awhile. If I diconnect the battery cable after I let it run awhile and leave it disconnected until I get ready to start it up again, it is OK. Could you give me a possible idea as to what is wrong. Any help you could give is much appreciated.
Answer: Not too much to go on, but here are a couple of things to eliminate before taking it to an electrical shop.
1st, pull the fuse pump fuse for overnight. When reinstalled in the morning and if the battery will start the car, then the fuel pump has been running overnight. That is usually caused by the oil pressure sender. Just replace it. This is the most likely culprit.
2nd, if above does not work, then pull both wires from the trunk light switch. That is a push pin mounted at the rear strut tower, drivers side, just in front on the trunk bulkhead.
If the battery continues to discharge overnight, then you should suspect the diode bridges in the alternator. They can allow charging when the engine is running, but may be a direct battery ground when it is not. That would take a good electrical shop to diagnosis.
It is also possible that the battery is becoming weaker over time, and is not charged enough during the infrequent use to maintain enough strength to start the engine. Remember, radio memory/clock, and ECM memory do put a light drain on the battery at all times.
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