alternater draw 2.6a but cant find a short?

[prove_it]

Quoting tektic:
Alternator is still drawing power. 2.6A to be exact. Here's the thing though. Its not a short to ground. So I Don't exactly understand what's happening. Testing current from the positive post on the alternator to the positive post on the battery with the rest of the car disconnected from positive I get 2.6a. Positive post to ground testing for resistance I get infinite. How or where is this circuit complete that it can draw power if not to ground?




Do you still have the negative cable attached? Also is the charge back wire completely disconnected?

 

[tektic]

There was no wire connected to the charge post of alternator but the plastic plug was connected in its socket. There were no wires connected to the positive battery post. amp meter in series between both mentioned points.

 

[prove_it]

When you unplug the connector, does the draw go away?

Sounds like the alternator is shorted internally to me.

 

[tektic]

I just tried... no change still drawing.

If it's shorting internally, wouldn't the positive post and the case show resistance less than infinity?

I just want to be 100% sure its the alternator before I order a NEW ac-delco Saturn unit. $240 is too steep for a new Mitsubishi.

 

[holeshotmoe]

If the two wires in the connector at the alternator are reversed, the field winding will always be energized, even with the ignition off. That would cause a continuous drain. Take look at the schematics. The S terminal wire should have continuous continuity to the lug at the fusible link box. The L terminal wire should have continuity only when the ignition is on. The ignition on condition energizes the leg feeding the alternator relay and CHG light, which in turn energizes the alternator field winding. A quick check:
Connect the lugs to the fusible link terminals and snap the 2-wire connector into the alternator. With the ignition off, touch a screwdriver to the bolt securing the alternator pulley. It should NOT be magnetic, i.e., screwdriver is NOT attracted to the bolt. Now turn the ignition on, and the screwdriver tip should now stick to that bolt on the pulley. If all works as described, it is still possible the two wires are making contact. This could happen if sometime in the past, there was a serious short in that circuit that caused the insulation to heat/melt, thus exposing the conductors to each other. And this condition could be intermittent, i.e., you hit a bump or move them around and they connect. You move them again and they flex just enough to move apart. To check this, perform the same tests above except use alligator clips to attach the meter leads, then begin flexing the harness at various points along the route these wires follow. As per the schematic, you could also make sure the relay's coil is NOT energized except when the ignition is on. That would help narrow down the location of any short between the two wires. I'm wondering about this because you said one time you checked and it was drawing current, and some time later you checked and it wasn't. In the last picture, note that the cable marked load is normally connected to the alternator B (output) terminal. Also, just FYI, there is a note in the manual that states "The generator relay functions as a back-up for the flow of electricity to the field coil if there is a disconnection or damaged wiring of the charging warning light." Doesn't mean much unless the field wasn't getting power and you were checking that branch (relay, fuse, and CHG light to field leg).

 

[tektic]

Damn. Thank you for taking the time to write that. I will perform theses tests and edit with my findings.

Results:
As soon as I connect the load (B) to the fuse-able link the alternator becomes magnetic with or without the charge plug inserted.

Further test of the charge plug show current at the first pin at all times and current at the second pin when MPI relay is energized.

Ruling out the charge circuit as a possible problem, I believe this concludes that the alternator is internally shorting. I will try a replacement parts store alternator and while it's out, complete preparations for the Saturn alternator swap by grinding my block and repainting the surface.

 

[holeshotmoe]

Glad to help. But sounds like you're on it man. CUH-razy it has a short like that. I once over-tightened an output terminal nut (on some alternator) that secures it to the end-case. Had a powerful drill with driver on it, set for the wrong rotation :-O It broke the insulator and then rotated full circle, breaking off the spot weld or the metal strap inside (IIRC). Anyway, the only other thing I can think to cause that is something dropping into the vents and lodging at the wrong place. If the thing has been working before, I'd crack it open and have a look. It's only four bolts...light hammer taps to knock the back off. Easy to put back together too. But you need a 6" piece of straight coat hanger wire (or similar) to hold the brushes in when you slip the back cover on. You-tube has couple vids.

 

[tektic]

I changed the broken insulator on mine and while removing it the post didn't seem too attached otherwise. I didn't think much of it, figured as long as power was coming out it was okay.

I'm not going to open it, just RMA it. I don't have much faith in these rebuilds, never did. I don't know why I bought it in the first place. I have 5 or 6 blown DSM alternators sitting in a milk crate in my garage. A testament to how well they are made. I'd like to try the new Saturn alternator, but I'm afraid its just a different animal and the same sh*t.

 

[prove_it]

Mitsu alternators will last, it's the removal of heat shielding and big downpipes that kill them.