2004 Kia Optima Keeps blowng 15 amp ECU fuse

BOBO09

MEMBER
2004 KIA OPTIMA
4 CYL
FWD
AUTOMATIC
106,000 MILES

This fuse blows intermettenly so I have not been able to drive the car for 7 weeks. Several mechanics have given up as they cannot reproduce the conditions to make it blows. There does not seem to be a pattern I can detect yet.

A wire comes off the alternator plug, through the 15 amp fuse, on to the computer. When it blows, it shuts down spark and fuel. It all started with a blown computer. I replaced it and it started right up but then started popping fuse as soon as you put them in, the 15 amp ecu fuse. I found a burnt wire leading to the fuse under the relay box on the fender, repaired it, everything seemed fine. Then the intermetten fuse blowing just when you don't want to be stranded. I can let it sit in my driveway and the fuse does not blow.

Could it actually be something as simple as the alternator going bad?

3 Replies

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Hello
thanks for the donation.

Your alternator has a built in voltage regulator and it has become faulty. It is obviously letting too much voltage through the system causing the wire to burn and the fuse to keep blowing. Replace the alternator and you will be good to go ;)

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Monday, February 16th, 2009 AT 9:16 PM

BOBO09

MEMBER
3 POSTS

The alternator seems like a likely target but it raises some questions like how did the power surge get past the fuse in the first place to blow the computer? Why did the fuse not protect the computer when this started.

And can the voltage regulator in the alternator go out intermettenly?

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Monday, February 16th, 2009 AT 9:23 PM

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Yes, if the regulator is bad then sometimes it may let the right amount of volts through and sometimes may let too much, causing the intermittent issues.

Fuses are meant to burn out if more amps are through the wire than is supposed to be, however, fuses are not instant. Some of the electricity may have had time to go past the fuse before blowing it causing the wire to burn and the computer to go out as well. Very rare, but it does happen. That is why when you cross polarize a car battery it can sometimes fry the computer. It SHOULD blow the main fuses before harming the computer but rare cases the computer and other components do get harmed.

You can always have the alternator tested if you would feel better than just replacing it.

Thanks for using 2CarPros. Com!

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Monday, February 16th, 2009 AT 9:30 PM