'95 Grand Marquis battery goes dead avout every 90 days!! How to diagnose?

My Grand Marquis has a good battery.

It has air suspension and every once in a while I hear the pump running when the engine is off.

Other than the draw from the air suspension compressor, I know of nothing else that would tend to draw the battery down.

When the battery is discharged, usually after sitting for a few days, there is only a click sound from the starter.

After I jump start it and run a half hour errand, it is fine for another 90 days or so.

I have a DC clamp on meter, nothing noted.

How would you go about diagnosing this intermittant electrical problem?

Thanks,

BoyntonStu

Reply to
Stu
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The air suspension is designed to stay active one hour after the key is shut off. I find mine usually pumps up a bit, then settles into "park height" at almost exactly 1 hour after I park it. The pump should never run after that until the car is started again (switch in run position).

I explain this so you can rule out the suspension electricals. I suspect the battery, simply because a very similar thing has happened to me. The battery had good voltage and the car started fine every day, every time, unless it sat for a few days. A good test, when you are parking it for a few days, remove one (negative) battery cable. If it's dead when you get back to it - bingo - bad battery.

How old is the battery, anyway? 4 years?, get a new one. This winter you'll thank yourself.

Paul in Dayton

Reply to
F&P

Thanks Paul,

Some more information. The problem happened with the last battery and with this new (under 1 yr) battery. However, I think that your suggestion is a good logical step to try. On the other hand, it will start up after a few days of sitting without disconnecting the battery. That is why it is so perplexing.

There is nothing in my experience to enable me to deal with this problem.

BTW, here in South FL the winter issue is not an issue.

Any other suggestions?

BoyntonStu (Boynton Beach)

Reply to
Stu

battery cables and every connection between them and the starter. Those bog bolted together connections can corrode and not have much visible difference. A little moisture or similar and they won't conduct. When it won't crank, have you checked the battery voltage at the batt? Maybe hold a voltmeter to the posts and have someone hit the key. A good battery will drop some in any case. I used to check it there and then get in the car and do the same check at the cigar lighter outlet. If it's wiring, that will show it up.

There could also be a problem in the alternator / regulator but it's not as likely these days with all the solid state stuff. I can't remember, have you done the test lamp test? You disconnect a battery cable and jump between it and the battery with a 12v test light. A glow is fine, full brightness isn't so good.

Good Luck - keep reporting, there are a lot of fairly smart folks around here...

PoD (new ID, same guy)

Reply to
Paul of Dayton

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