Alternator causing amp draw

[jeffball610]

A common swap for the 4G63 community is to use a GM alternator from a Saturn for more power and better reliability. However, I noticed that after my swap, I was getting a dead battery within a day or two even though it was putting out the required power when running. I did an amp draw test and found a 4.5 amp draw from the alternator "sense" wire hooked up the alternator "F" post. Disconnecting it gets rid of the draw, but also does not allow the alternator to put out the required amperage to charge the battery. A quick search says some alternators could have a bad diode, but this is a new unit and "should" likely work just fine.

 

So I'm at a loss with my current knowledge base. I can get the alternator checked, but if it tests good, then what are some likely culprits to this amp draw? I know my grounds are good. My wiring should be solid. Do I even need that wire? Some sources say "single wire", but I'm not getting 14v when running without it. Grrrr.

 

 

[DanielC]

On internal regulated alternators I am familiar with, the two or more small connections have to be disconnected from power when the key is off.

 

I assume you are using the charge light to power the light connection on the alternator.   The sense connector needs to be moved to a switched side of the fuse box.

 

A 4.5 amp draw sounds to be too high for the current the circuit in the alternator would need to measure the voltage.  I would disconnect the two small wires, recheck current draw, and with the ground wire, from the frame of the alternator and the positive output wire both connected check for current draw.  That tests the diodes, and if there is a current draw, one or more diodes is bad.

 

There is a ground wire from the frame of the alternator to the voltage regulator, that attaches to the inner fender.  This wire must remain on the inner fender.   It grounds body sheet metal to the engine, and battery. 

[banzai510(hainz)]

is this a 510? the car doesnt know what motor is in there. L20 L16 ect............

 

 If one does the IR conversion the 72 with auto choke shorting the BW to W/R and white with yellow. I hear of the choke relay heater being the draw.

This must be discconnected.

 

not famliar enough with the GM alt but they say the conversion you have with the sense wire is better than the one wire.

[thisismatt]

Sense wire should be hooked up to a switched source, ideally a run through your ignition switch.

[Draker]

Is it a NEW unit.. or a new to you, rebuilt unit?

[jeffball610]

This is a new alternator. I've done some more research, and it appears the "sense" wire does need to be switched with key on. That would resolve the amp draw when off. I think stock, the 1st gen 4G63 that I'm using, does have a dedicated fuse and relay. I thought I was being clever by being simple, but I guess not. I'll do some testing over the next few days and see what happens.

 

For reference, this is a 510 with a complete rewire for a Mitsubishi 4G63T and a GM Saturn alternator. Battery has been relocated to the trunk.

[banzai510(hainz)]

well most of the cases wireing stays the same I would think for the car.. You just use a relay to trigger a new harness for the motor/electrics.

But if this works you got it

[Lozer]

if the diodes are toast it will draw when off also.