[Healeys] Electrical problem diagnostics

Dave Porter frogeye at porterscustom.com
Tue Dec 1 12:10:46 MST 2009


Why not just use an ammeter?
dave

frogeye at porterscustom.com

Porter Customs   2909 Arno NE
Albuquerque, NM USA 87107
505-352-1378
1954 BN2  1959 AN5
Porter Custom Bicycles

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-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at autox.team.net]
On Behalf Of Richard Dryman
Sent: Tuesday, December 01, 2009 11:31 AM
To: healeys at autox.team.net
Subject: Re: [Healeys] Electrical problem diagnostics

This is EE101 applied to a car battery being discharged when the car is
parked
and not driven & isolating the current drain circuit when not obvious. With
battery shutoff switch and lack of fused circuits it is not as applicable to
AH as to others but it is definitely a procedure to remember, for shorts,
electric device current draw (not starter), etc. Also the double connectors
in
the AH can isolate circuits as per elec. diagram.
Go to a Radio Shack & buy a
2 pack of 1.0 ohm, 10 watt resistors. 
http://www.radioshack.com/product/index.jsp?productId=2062290  They cost
$1.99.  Wrap the leads of the 2 resistors together(wiring in Parallel)to
make
a 1/2 ohm resistor and then attach a alligator clip to each end, big enough
to
clamp on the ungrounded battery  post (after disconnecting that battery
cable.  Note: battery disconnect switch should be 'on' and ign. switch
'off'.
Connect one alligator clip to the battery anode and the other alligator clip
to the removed battery cable( best to be on 'hot' post not ground).  This
will
put a .5 ohm resistor in series with the removed battery cable.  You
absolutely have to have a voltmeter of some sort, a good digital vom is dirt
cheap.  Set the voltmeter controls to measure voltage, connect one lead of
the
VOM to the battery alligator clip and the other battery lead to the + cable
alligator clip(parallel with the resistors).
  Using ohms law I=E/R where R
will be .5 ohms wired as shown, just reading voltmeter will tell you how
much
current draw you have from a short or something left on .  For example, if
the
voltmeter reads 5 volts,  5V/.5ohm= 10A current draw.  Then start pulling
fuses; when you pull the right fuse the voltage will drop drastically,; look
for a problem in this circuit.
  If no change or very little change in voltage
when you pull a fuse or connector, it's the wrong circuit.
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