Parasitic drain on battery

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Texx

Texx

Joined
Feb 27, 2002
Threads
168
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WTF!!!! After owning my daughter's 85 for several months without a problem, battery was dead friday night (happened while driving!) The truck began to buck, she pulled into a parking lot and shut it off, and nothing. Barely a click. I bought a new battery , although the old one tested good, installed it, and she drove it a couple of blocks sunday. This am, monday, it's totally dead. While having the battery tested the tech noticed a 5 amp drain on the battery. It's totally stock, with no accessories except the radio. Radio is not on a hot circuit when key is off. Any ideas why this would occur all of a sudden, happen to anyone else, and where to start?
 
radio is a hot circuit when the key is off - it has to keep the pre-sets and use juice for the clock (if so equipped). But you're right, that's a ton of draw. Ironically, I have the same issue right now....
 
might be able to go around with a volt meter while the vehicle is turned off and try to pin point where the current is going. If my limited knowledge of electronics serves me right you should be able to pull one fuse at a time and measure the voltage, if you find one with voltage(while car is off) then you have located a place where current could be going.

I beleieve there are a few things that draw very small amounts of current all the time, like the clock.

Drawing that much current you might feel around for warm things even.

hope everything works out for you. :cheers:
 
Get ahold of a decent ammeter, put it on the + lead to the battery (has to be wired in series). Measure the drain on the battery. Then start pulling fuses until the drain goes away. This will tell you which circuit is the culprit.

Wiring on an '85 is pretty simple, once you know the circuit it should take long to find the fault.
 
PurpleFJ62 said:
might be able to go around with a volt meter while the vehicle is turned off and try to pin point where the current is going. If my limited knowledge of electronics serves me right you should be able to pull one fuse at a time and measure the voltage, if you find one with voltage(while car is off) then you have located a place where current could be going.

I beleieve there are a few things that draw very small amounts of current all the time, like the clock.

Drawing that much current you might feel around for warm things even.

hope everything works out for you. :cheers:
Click to expand...
Actually you want to measure the Amperage. Pull each fuse one at a time, put an amp meter across the two fuse connectors at the fuse block. 5 Amps is a very large draw. The radio on at full volume probably does not draw 5 Amps.

Good Luck

JB
 
I know the old chevy alternators would do that if they burned a diode in the rectifier.

Is this a possibility in out alternators?
 
sorry for telling you the wrong info there. Dident mean to. I have never seen an ampmeter before, but its probally just like a volt meter. Sounds like a good tool to have around the shop.

boy oh boy do I feel like an idiot, thats what I deserve being 18 I guess.
 
Guys, thanks for everyone's help. I literally felt like I was chasing a demon around inside the truck. In the process I lost the a/c blower, stereo, left front headlight, left turn signal bulb, half of the fuses on the fuse block. Short lesson learned: Never trust the "on car" test done by the low buck morons at the local auto zone type place. Battery was tested good, as was the alternator, so I went beserk trying to find a short, pulled the taillights, marker lights, searched for and removed non stock wiring in the harness, nothing solved it. Went through two guaranteed batteries in the process. It'd go so flat overnight, the battery couldn't be recharged. Finally a friend with a amp meter and I went over the truck. Moderate drain at idle. HUUUUUGE spike as soon as the throttle was touched. WTF? Check voltage at the battery. 17 volts! Waaay too much! Fried voltage ruglator in the internally regulated alternator. New alternator, and life is good! No more drain. buy a headlight, replace a blower fuse, (that tested good with the old alternator???). Life is good. Sorry for writing a book..hope if helps someone else out there.
 
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