Battery drain: 500mA current draw from AM1 fuse (1 Viewer)

[TrickyT]

...Here's some more info for you: assets.fluke.com/appnotes/automotive/beatbook.pdf...

Lot's of good basic tips for checking out vehicle electrics in that PDF. Thanks for posting!

 

[David60series]

Thanks.

I provided readings with alt disconnected also as described above.

I cannot get a resistance reading in the forward position.

 

[David60series]

The full drain is showing through the charge lead at 500mA. I guess this was already confirmed earlier when I ran the ammeter through -ve battery and removed charge leads.

I can confirm that there is no current drain when the 3 pin plug is removed, but the charge leads remain.

Is the S pin meant to provide constant voltage to the reg even when key is off?

I would have thought if the reverse direction resistance test came in at 125 000ohms, then a diode would not be the problem?

George - no auto electrician in my town.

Dave

 

[george_tlc]

Well, given the parasitic current issue occurs when you connect the alternator, there IS something wrong with it or the regulator. Testing diodes is best done with the diode position on a multimeter since it applies a voltage that should turn on a diode (diodes have a forward voltage drop).

Not sure on the toyota and your aftermarket alternator, there's usually 6 diodes for the 3 phase windings to create DC (pseudo DC) from the AC. There's also usually a diode trio that provides voltage to the regulator and warning light circuit.

Time to move to a bigger town Oh, it wouldn't hurt to add your vehicle specifics, location etc into your signature and profile...

cheers,
george.

 

[David60series]

Meter in Diode mode:

OEM alt (no drain when last removed)
Black probe stud/red probe case = 0.501 (no short or open circuit)
Reverse configuration = 1 (diode good)

NEW SBC ALT
Black probe stud/red probe case = 0.410 (no short or open circuit)
Reverse configuration = 1 (diode good)

As previously advised, diodes are 12x sanken 40amp after market unit.

Can anyone advise if terminal S on 3 pin plug should have constant power with key off?

 

[george_tlc]

Well, on a petrol 80, the S pin connects directly to 12V via fuse AM1 and fusible link AM1.

Well, if you can pull the diode 'pack' out of the alternator, check each one individually.

cheers,
george.

 

[David60series]

I reckon it is as simple as the adaptor lead being assembled in the incorrect configuration, with the S sensor on the factory loom wire feeding the excitor on the reg while the car is off.

I don't have a schematic of the new alt, but I reckon that is it.

 

[David60series]

For those interested, this turned out to be the issue. The adaptor plug was shipped in the wrong configuration.

Five minute fix after days of chasing my tail.