Date: Wed, 25 Aug 2004 16:01:58 -0500
From: "Rex Chalmers" <alfasport@domain.elided>
Subject: [alfa] battery drain
Greetings Alfa Digesters,
I've been reading all the discussion about battery drain on Bosch injected
cars with much interest. I have had some experience with this problem and
have been using a diagnostic test that works quite well in most cases.
First, a few caveats;
1. Don't perform any amp or voltage draw test on a freshly re-charged
battery. If you have to re-charge the battery, give it a day with the
negative cable disconnected to stabilize the charge before you test.
2. Don't turn the engine over or turn on engage any equipment or accessory
that will draw much over 6 or 8 amps during this test as it will probably
damage your multimeter, or blow the meter's fuse at a minimum.
3. I have found that most Bosch ECUs will draw between 10-20 mA at all
times.
4. Most non-Bosch Alfas draw around 150 ma at rest.
5. Most Bosch injected Alfas draw around 170-180 mA at rest.
The Test;
1. Insert the red test lead to the A or mA socket of your multimeter, insert
the black lead to the "Com" socket.
2. Disconnect the negative cable of the battery. Connect the Red lead to the
negative terminal of the battery and the Black lead to the negative cable
terminal end.
3. Position the multimeter switch to "mA/A dc" position.
4. The reading should be between 150-180 mA, yours is probably higher if you
are performing this test as your Alfa is experiencing a current draw.
5. Start pulling fuses one at a time until you find the circuit that is
causing the current draw.
6. If you aren't getting any current drop from any of the fuses, you will
have to look at circuits that are not fused: Alternator (on some cars),
starter, or possibly one or more ECUs.
A word of advice: check the brake lights! I would estimate that one car in
five that is brought to me because the battery is going dead over a few days
or less is due to a maladjusted or faulty brake light switch. I have seen
ECUs that for some reason have inordinately high draw even though the unit
is functioning perfectly otherwise. I would suggest that all Bosch injected
Alfas, or any car that sits for more than a few days, would benefit from
the installation of a battery cut off switch of some type. I generally
install the adapter switch that is intended to be installed on the negative
terminal of the battery. It's much more economical than replacing an ECU or
a battery.
Ciao
Rex Chalmers
65 Giulia Sprint Speciale
66 Duetto
86 Milano
91 164
92 164
03 SVT Focus
www.alfarex.com