1991 olds 88 battery runs down over night

My 1991 olds 88 battery runs down over night. 2 shops looked at it and couldn't find the cause. Anyone have suggestions for cause or of ways to trouble shoot the problem? Thanks

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Remove the battery from the car, charge it and see if it holds it's charge. If it doesn't, the battery is not in good health.
Dan

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Sorry,,don't have to remove the battery from the car, disconnect the negative and you can charge it directly on the car to perform that test.

and
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jmsmith wrote:

It is possible for an old battery to become "sulfated". The lead plate chemistry gets screwed up, and the battery will self-discharge overnight. In a few cases, I've seen somebody add extra H2SO4 and recover the battery performance, but in most cases, it is a waste of time. Fortunately, lead batteries are easily recycled and new ones aren't terribly expensive. When I buy a new car battery, I figure that it is good for about four years or else four complete discharges, whichever comes first.
---Bob Gross---
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Hook up an ammeter in series between the battery and one of the cables. Current draw shouldn't be much more than 50mA. 300mA would be enough to drain the battery overnight.
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If he took it to two shops they should have load tested the battery......

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My 1991 olds 88 battery runs down over night. 2 shops looked at it and couldn't find the cause. Anyone have suggestions for cause or of ways to trouble shoot the problem? Thanks
Thanks for all your suggestions. Some updates: I tested the batt. with a load tester and it is OK. The alt. puts out 14.8. Disconnecting the batt and putting an amp meter in series shows no current draw. However, starting the engine and then shutting it off causes a the thing (maybe idle air?) to click that is just aft of the throttle body and above the crossover pipe on the left side of the engine. It has a 4 wire connecter that plugs into it. It doesn't click after the batt. cable is disconnected then reconnected. I started the engine, shut it off and the thing clicks again. I tried reading codes but the check engine light doesn't come on. This may be part of the problem or just a dead bulb. I bought a shop manual but it won't come for a week or so. The car starts and runs fine, but I only drove it about 10 miles before I bought it.
Thanks for reading this and thinking about it.
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Zero current draw? There should be some (at least 10mA or so). Sounds like you may have an issue with your ammeter or with the hook-up.
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You are right. The meter I was reading with has a/c amps. The other meter reads 7.9 mA. The solenoid clicking didn't occur though so the load is other stuff when the engine hasn't been run. Thanks

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