alternator swap

[89Ru]

2002 Outback H6 Sedan suspected alt failure. Can I swap out a known working OEM alt from a 2007 Outback 2.5L after swapping the pulleys?  Looks like output current is about the same 100 on the H6 and 110 amps on the 2.5L.  Connectors look compatible. 

The background. Batt and brake lights lit on dash on a road trip, driving fine otherwise, headlights shut off (at night of course) and car dies about 30 min later. Presumed alt failure, is a reman unit, about 5 years old. Battery is 2 years old. Charged battery to 12.8v using external charger. Installed a reman unit from parts store.  Car starts and alt charging at 14.x volts, dash lights back to normal. At some point during 10 minute idle, alt stops charging. Batt voltage drops to 12.x volts and headlights (normally on while car running) turn off. Batt and brake lights on dash as before. Battery/alt/starter harness replaced about 5 years ago. 

Could there be some other failure that killed the new alt too? 

Going to bring failed alt to parts store and get it tested, get replacement if possible but if that falls through I have a spare alt from the 2.5L.

[1 Lucky Texan]

I don't think so. The H6es get ECU control of the alt.

best bet, find a local rebuilder and have your original alt. rebuilt. unless of course, it was already given up as a core.  car may be down a few days.

or

check into parts from DB electric or Maniac motors(?) in Texas.

even an alt from a wrecking yard (must be H6) is preferred over any alt from typical parts retailer .

Edited October 4, 2023 by 1 Lucky Texan

[89Ru]

Ok. I had heard about H6 alt needing ECU input so thx for confirming. This alt is already aftermarket so must have gotten lucky in the past. Local yards are pretty picked over but might try my luck again. This was a sunday night save the day job or so I thought. 

https://www.maniacelectricmotors.com seems to sell rebuild kits. Haven't been able to get enough heat to disassemble the electrics.

Local alt rebuilder hasn't updated FB page in 5 years and phone is disconnected   If anyone knows a rebuilder in Nashville lmk. 

https://www.dbelectrical.com ships overnight. looks like my best option for the H6. 

[idosubaru]

4 hours ago, 89Ru said:

Ok. I had heard about H6 alt needing ECU input so thx for confirming. This alt is already aftermarket so must have gotten lucky in the past. Local yards are pretty picked over but might try my luck again. This was a sunday night save the day job or so I thought. 

https://www.maniacelectricmotors.com seems to sell rebuild kits. Haven't been able to get enough heat to disassemble the electrics.

Local alt rebuilder hasn't updated FB page in 5 years and phone is disconnected   If anyone knows a rebuilder in Nashville lmk. 

https://www.dbelectrical.com ships overnight. looks like my best option for the H6. 

I think DB is also in TN, so you'd be supporting local. They're pretty popular in subaru forums, probably still not OEM quality but they've been around quite a few years now and have good recommendations. 

[89Ru]

Yes, DB is in Kingsport. I supported my local parts garden and scored an H6 alt. While the H6 and 2.5L alts both have a 3 pin connector, it appears that only the H6 uses all 3 wires in the harness. I noted that a 2006 Forester 2.5L 3-pin green alt connector only has two with populated pins on the harness pigtail. That being said, I wonder if the H6 alt could serve as a spare for a 2.5L model? Parts store says they will take the reman alt back. 

[89Ru]

Up and running with the DB alt. Windings of the reman alt look blackened. So wondering if a winding shorted out since it was charging for a few minutes.