Parasitic Drain - Bulb Trick

A wet battery top with electrolyte on it can do this. Washing the battery
periodically is a real good idea.

Earle

 

I forgot to add "volts" so it would read "and the DMM measures VOLTS across
the 1 ohm resistor."

< Since I=E/R,1 volt across 1 ohm= 1 amp.

 

I forgot to add "volts" so it would read "and the DMM measures VOLTS across
the 1 ohm resistor."

< Since I=E/R,1 volt across 1 ohm= 1 amp.

 

....and be careful. If you by some mischance get it across the battery it
will try to dissipate I^2*R W. One ohm at 12V passes 12A, so thats 144W,
well in excess of the 10W its rated for. It will get red-hot and fail in
some interesting way, quite suddenly...

 

....and be careful. If you by some mischance get it across the battery it
will try to dissipate I^2*R W. One ohm at 12V passes 12A, so thats 144W,
well in excess of the 10W its rated for. It will get red-hot and fail in
some interesting way, quite suddenly...

 

So,if you're that inept,put a 3A fuse in series with the resistor,like many
DMMs that are fused for the current ranges.

Of course,any ammeter would also be a short across the 12V.

 

So,if you're that inept,put a 3A fuse in series with the resistor,like many
DMMs that are fused for the current ranges.

Of course,any ammeter would also be a short across the 12V.

 

Hello again, I was the original poster of this thread. I'm posting an
update to the problem, for those who are interested.

After disappearing mysteriously, the parasitic load was back again last
night. Today I've finally found the problem. It's the *alternator*. I
found it by disconnecting the alternator ground. It was very hard to
find before because it was intermittent, but it's definitely the
alternator.

Bad alternator diodes..? I recall the problem started just after an
engine wash..

Thanks.

 

Hello again, I was the original poster of this thread. I'm posting an
update to the problem, for those who are interested.

After disappearing mysteriously, the parasitic load was back again last
night. Today I've finally found the problem. It's the *alternator*. I
found it by disconnecting the alternator ground. It was very hard to
find before because it was intermittent, but it's definitely the
alternator.

Bad alternator diodes..? I recall the problem started just after an
engine wash..

Thanks.

 

Thanks for posting back how it went and the fix.
The ones that come and go are the hard ones to fix.
You just have to catch them when they are doing it.:grinyes:
Glad all is well.
MT

 

UPDATE:

For those interested, the problem is finally resolved. I was the thread
starter, asking about an intermittent parasitic drain that can't be
found. I finally isolated it to the alternator; and today, after a day
of trying, finally got the alt off. Brought it to a shop, and they
diagnosed the problem as "grounded rotor". Regulator, diodes all
checked out fine. They replaced the rotor with an identical (Nippon
Denso) rotor, and now there is optimal current drain and no parasitic
load. Total cost, including labor (if converted to US$): $24.

Thanks to jim, TeGGer, Earle and all the others who replied. More power.

 

UPDATE:

For those interested, the problem is finally resolved. I was the thread
starter, asking about an intermittent parasitic drain that can't be
found. I finally isolated it to the alternator; and today, after a day
of trying, finally got the alt off. Brought it to a shop, and they
diagnosed the problem as "grounded rotor". Regulator, diodes all
checked out fine. They replaced the rotor with an identical (Nippon
Denso) rotor, and now there is optimal current drain and no parasitic
load. Total cost, including labor (if converted to US$): $24.

Thanks to jim, TeGGer, Earle and all the others who replied. More power.