I recently started blowing my engine fuse randomly. After some searching on here decided it may be my alternator. Took it off, had it tested and of course it failed. Took it to a reputable shop locally, and had it completely rebuilt, (bearings, brushes, stator, slip rings) with new denso parts. Also had it bumped up to 100A and had it tested to be sure. Works great. Put it in, charges like a champ and then a few miles down the road the engine fuse blows again. Do I need a larger engine fuse for the increased amperage of my new alternator or should i be trying something else. Any help would be awesome. Thanks in advance.

 

what motor?

 

Its gotta be the new alt.

 

22re, and it was doing it prior to the new alternator. thats what made me think it was the alternator. i meant to say new rectifier as well. the alternator is fine and im sure of it, but any other ideas?

 

The alternator will only put out 100A if it's full fielded or it's keeping up with a draw close to it's max output, so it only puts out as many amps as needed to keep the battery charged, so the fuse blowing has nothing to do with a higher amperage alternator, fuses blow due to high current draw, either a short or or a component in the circuit is drawing too many amps for the fuse to handle, I doubt you can fix this by replacing parts, unless you know which part is the culprit.

 

The "Engine" fuse does nothing but power the field winding of the alternator ("IG", red, pin 2 in connector). (How did they ever come to call the alternator field fuse the "Engine" fuse?)

The alternator doesn't "put out" anything through the field winding through the Engine fuse. You've just got an intermittent short someplace, almost certainly between the alternator and the Engine fuse. The truck jiggles, it shorts to ground, and blows the fuse.

It could be anywhere in that single wire, but given that you just replaced a bad alternator, my guess is that it is right in the connector.

 

well fellas i think i may have found it tonight. I went out while it was dark to tinker on it, and figured that everytime i put it in reverse it blows the fuse. Just gotta track that down now

 

Has there ever been a trailer kit added to your tail lights? If so, I guarantee that's your issue.

ALSO, the EFI fuse is often blown when the O2 sensor wiring lays on the muffler & gets burned through OR wrapped around the drive shaft & ripped apart~

 

Dead thread...
Post transferred to my build thread because I also need to fix mine.