Finding an electical short?

I seem to have a short in my 1990 Honda Accord EX. I had some problems
with the car starting back in January so I got a new battery. I've
still had problems since then. What happens is the car starts fine
each morning or during the day. However if I don't start the car for a
while (say four or five days) then the car probably won't start. If I
get someone to give me a jump then I can start the car fine, and I'll
have no problems so long as I start the car at least every couple of
days. I've checked all of the normal problems like lights being left
on.

So, does it seem like it is a short? It sure seems that way to me, but
I'm not sure how to go about finding the problem. Everything seems to
work fine on the car so it's not something obvious. Any suggestions as
to how to find and fix the problem?

 

It's not a short. If it was a short, you'd have a blown fuse or fusible
link and possibly some burnt wiring if the fuse was the wrong size.

What you have is a device that is connecto the battery all the time and is
drawing too much power when off. Devices that connected directly to the
battery include the engine computer, radio, clock, alternator, and other gizmos
like a car alarm. The battery itself might have enough crud on it to run it
down.

To troubleshoot, disconect the positive battery cable. Measure ohms from the
positive battery cable to ground. It should read at least 500 ohms, preferably
a K or two. If it reads below 500 ohms, start pulling fuses till you narrow
it down. I usually pull an entire row at a time putting them down on a flat
surface in order. If row #1 doesn't have the culprit, I put them all back and
go on to row #2, etc. Disconnect at the alternator the wire going from
alternator to battery and test.

 

Check the courtesy light in the trunk and on some cars there's one in
the glove box too.

Or disconnect a battery cable and put an ammeter in series to see what
the load is, then start pulling fuses. Worst case could be a bad diode
in your alternator.

 

FIRST thing to do is get the battery tested! Even a new battery can be
bad! If the battery is on it's last legs, it can exhibit the exact symtoms
you describe as it slowly gets worse.

IF it checks out OK, you can try removing one fuse at a time to isolate
any parasitic draw with a Voltmeter. if you don't have a meter, leave out
1 fuse at a time when the car is sitting to isolate the circuit. You may
loose your radio presets etc.

DO NOT use OHMs on a powered circuit.

 

I once had a car where the mercury switch in the trunk lid was not
working and the trunk light stayed on. If you have a fold down back
seat open it and see if the light is on.

 

Well it can't be that as the problem. The light is missing from the
trunk. I knew it hadn't worked in a long time, but I didn't realize
the light was actually gone from there.

 

Please see Section 10 in the Car and Deep Cycle Battery FAQ on www.batteryfaq.org.

Kindest regards,

BiLL......