I used to fight this problem every Spring and Fall (temp change). The
cure is to totally disconnect the battery cables, use a terminal brush
(inside and outside), reattach and coat with grease to seal out the air.
The corrosion causes high resistence that lets the radio and lights to work,
but won't permit cranking the stater.
Also, one time the problem turned out to be a slipping fan belt. The
alternator wasn't recharging the battery.
Damn complicated cars! But that's good advice. He might want to ask
the dealership about what he can expect to happen when the battery is
disconnected on his particular car. The fancier it is and the more
accessories, the more things are likely to happen.
You need to check the power seats. I had a car before that the power seat
control did not always stop and the motor had a small draw sometimes killed
2 batteries before I figured it out. I would try pulling the fuse for the
power seats! Especially if the seats move back when you turn the engine off
for easy exit!
Well, a damn simple "no additional equipment needed" test would be to
just disconnect one battery cable, let things sit for 3 days and then
reconnect it. If the car starts like a charm, you have your answer. If
it won't, it's the battery.
But, it sure sounds to me like the guy you're talking to at the dealer
had his alimentary track completely reversed.
Jeff Wisnia (W1BSV + Brass Rat '57 EE)
"If you can smile when things are going wrong, you've thought of someone
And he loses his radio when the anti-theft memory code is lost.I hope he
keeps the code where it will not get lost.Also,the EFI may lose it's
calibrations,and revert to open-loop operation for a few days.
If the dealer did an amp/hour test is sounds like he really tested the
battery. However, you can prove whether it the battery or parasitic
draw by simply disconnecting one pole checking the voltage after 6
hours and use that as a base and then checking the voltage after 3
days. Harbor Freight has cheap digital voltmeters ($4.00) if you
don't have one. If there is any significant change in 3 days you have
a bad battery. Full charge should be around 12.75 V at full charge.
And of course while the battery pole is off you can connect your
voltmeter between the pole and the cable (in series) to measure the
amps. (be sure you pull the hood lamp when you do the test. Any
significant amperage will be bad.
As an example, my F-150 truck will sit for 2 months and not drop more
than 0.3 V. I once installed a replacement radio in a vehicle and
found that it drew so much power when off that voltage was low enough
to make starting hard when left for 2 weeks. I liked the radio so I
installed a switch in the hot lead and turned it off anytime I was
going to let the vehicle sit for more than a day. Of course in lost
memory of stations when switched off, but then I only listen to one
station most of the time.
Once the voltage has settled to a "during-discharge" voltage as opposed
to one for "during charge" or "recently charged and not discharged since",
light loads (a couple amps or less) do not have significant effect on the
voltage at the battery terminals.
A car battery approx. 82-85% charged when being charged with just an amp
or two has about 13.8 volts, and when discharging that much current has
about 12.6 volts.
But if you measure the voltage somewhere other than the battery
terminals themselves, voltage drops due to current flowing through wiring
or through coroded connections may be significant.
Another thing: Battery condition, temperature and other factors can
have a major effect on what percentage of full charge you need to start
- Don Klipstein ( email@example.com)
I should have noted in my original response that you may also have a
problem with the charging system. It may not be charging fully.
Many auto parts stores will check the battery and charging circuits for
free. It is not 100% certain, but they get it right most of the time.
Thanks to all you guys. I am in the process of checking all out. I
have disconnected the battery, checked the cold cranking amps and
also the current draw. I have some good meters left over from my
The CCA is at now at 365 .. not a full charge but enough to start the
car. The current draw starts at .67 amps and drops slowly to about
4.6. I will leave the battery disconnected until Monday. If the CCA
remains unchanged that should rule out the battery. I will then start
pulling fuses, etc. I shall also contact the dealer to make another
appointment. I have printed out all your notes to take along. I have
not decided if I will highlight all of your opinions concerning the
service manager ;-)
I did check the entire car in total darkness and see no lights on ..
When the problem is resolved I will post the results.
Again .. thanks to all.
It drops from 0.67 amps TO 4.6 amps? That's an increase,not a drop.
Or do you mean 6.7A to 4.6A? That's a pretty hefty current draw,IMO.
It should be less than 1 A,I believe.
I will leave the battery disconnected until Monday. If the CCA
A common problem in cases like this is a bad alternator. Blocking diodes can be
leaky and cause just such drainage. Used to be a common problem in Nissan
vehicles some years ago. The easy check is to simply disconnest the alternator
lead wire at the unit or cable connector, whichever is handier. Let things sit
for a period of time and test for starting abilility. Doesn't drop computer or
radio codes either.
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