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Forum namePerformance/Engine
Topic subjectalternator fuse shot
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i5&topic_id=104064
104064, alternator fuse shot
Posted by 95RS_oversees, Apr-29-07 07:31 AM
DSM Guru's, I need some help!

A little trouble history first (the car was standing still for a few months):

I had some trouble to keep my car running idle, and, while driving, the engine did not allow to rev up above 3500 anymore, stutters, and if pushing the clutch pedal it died. Replaced my IAC motor, cleaned out the TB, no result. (Key danced) DTC code 25, 14. So replaced the MAP sensor as well. Started, still 25 and 14, rough idle!
Swapped out the ECU (still had an old ECU which ran fine in the past, but did not have the 2nd air update). The DTC 14 was gone (of course, the 36 was there again). Hooked up my current ECU again. Guess what?? The 14 was gone as well!! Car idled fine, took it for a spin. No problem detected. I guess combination of MAP sensor and some bad contacts in the connector of the ECU.

Got to work fine, however, when returning, at the highway, it felt like I was driving over a bumpy road, engine just did not give it all. Also the batt. light came on, and eventually when I pushed te clutch again, it stalled. Fired it up, it drives, but not sweet as usual and everytime stalled at the light. So imagine the car fires from the battery, and the ECU timeslots for the fuelinjectors widens so that's why it drives so crappy, right?

Anyway, after checking the usual (corrosion on cables and connectors) checked the batt. voltage, just fine at 12V. Fired up the engine, power dropped to 11V! So the alternator was not charging the batt. Checked the fuses. The 120A alternator fuse was shot.
One side there was the 11V (the batt side I guess), the other side 0V.
- Should that not have to be the higher alternator voltage? - why would the fuse blow, could that just be over time (realizing it is a 95)? I did not detect any short circuit (yet)...

I know it's a long story, but thanks for helping out!!
104065, RE: alternator fuse shot
Posted by Star Turbo Talon, Apr-29-07 04:54 PM
Replace the fuse and try it. A few people have blown that fuse and no explaination was ever found.

As for no voltage on one side, thats normal. The ECU will shut the Alt down if battery voltage is not detected back at the alternator (backfeed)

Now, things to check. Check all conns at the alternator, make sure they are clean and tight. You already checked the battery, thats good. Check the harness to the alternator and make sure there arent any abrasions on it causing a short.

Terry
104070, RE: alternator fuse shot
Posted by 95RS_oversees, Apr-30-07 12:42 AM
Thanks for the explanation, Terry! Appreciate it! Will replace the fuse and just check (why do important shops always close on sunday...)

Right as you mentioned, first thing I did, was cleaning the main cable at the alt., and put contactspray on it to keep clean. Also checked the harness on the alternator, no damage to see.

By the way, is the bumpy, stutterly behaviour explained by the absence of the alternator functioning? So the injectors are triggered somehow wrong?

Thanks again,

Jeronimo