alternator blows fuse upn rev - Automotive Wiring and Electrical


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alternator blows fuse upn rev

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rickknecht
New User

Jun 9, 2010, 10:01 AM

Post #1 of 4 (3837 views)

alternator blows fuse upn rev	Sign In

I have a 1990 Jeep Wrangler with the 2.5 four cylinder. Ran very good. I noticed the ammeter gauge started to get lower and lower over about a week’s time. Then one day it dropped to red and I barely made it home before battery was dead.

So I figured it needed a new alternator. Took it to Advanced and they tested it first time and said it was fine. I put it back on. The Jeep has a fusible link that contains a 30 amp fuse in the wire path from the alternator to the battery. This fuse was blown. I replaced it. But the fuse blows again if you rev up the engine. As long as you don’t rev the engine, the ammeter shows proper charge. But rev the engine and the fuse blows and stops the charging altogether.

Took alternator to different store. They tested and also said it tested fine. But then they said there was a crack in the alternator case. So they got me to pay $80 for a new alternator (which is non-returnable by the way). Installed the new one and it does the same thing. It blows the fuse if you rev up the engine. Funny thing is that nothing else is affected by this blown fuse. Jeep runs and drives with all accessories even if the fuse is blown. Only charging of battery is affected. I can drive it as long as I manually charge the battery.

Any ideas?

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 9, 2010, 10:11 AM

Post #2 of 4 (3829 views)

Re: alternator blows fuse upn rev	Sign In

I don't know where you got the idea this takes a 30amp fuse but it has to be bigger than that. This is most likely a 65 amp or higher alternator and will need a fuse to carry that much. I would replace it with approx 12 gauge fusible link or a 50 to 75 amp fuse.
It will have either a fusible link or a fuse but it won't have both.

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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

(This post was edited by Hammer Time on Jun 9, 2010, 10:12 AM)

rickknecht
New User

Jun 9, 2010, 10:18 AM

Post #3 of 4 (3825 views)

Re: alternator blows fuse upn rev	Sign In

Two months ago the Jeep had a short while installing fog lights and melted two fusible links. I replaced with this 30 amp inline fuse link. This was the only fusible link they had at the time. It ran like that for two months with no problems.

Thank you for advice. I will replace with a high amp fusible link.

Thanks again.

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 9, 2010, 10:21 AM

Post #4 of 4 (3822 views)

Re: alternator blows fuse upn rev	Sign In

That is not a fusible link. That is just a fuse and too small of one at that. A fusible link is a special piece of fuse wire that melts when overloaded and that's what's supposed to be there

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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

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