Blown alternator fuse

[mantiaGT]

Hello,

I do have a 99 GAGT but the problem I have is with another GM car I have. A 97 Cadillac Catera. The fuse is 20 amp and it keep blowing. The alt is new and I just replaced the battery. This is the third battery since April. I am guessing it's a wiring problem. Is anyone familiar with this and is it expensive for a mechanic to look ot it? Also this morning I replaced the fuse for the third time in maybe 3 weeks.

Thanks in advance.

[rixGAphx]

It's blowing a 30 amp fuse.
OK.

There aren't many 30 amp circuits on modern cars, even caddies.
That's a lot of power for a circuit.
But nowhere near enough for an alternator.

What circuit does the 30A fuse serve?
There should be a 5 or 6 letter name next to the fuse slot, like 'HDLMP' or CRTSY or such.

It is NOT the 'fuse for the alternator'.
Alternator's don't have fuses.
They have a 'fusible link' or similar, but not 30 amps [edit].
More like 130 amps [edit], since that's how much power a smallish alternator (like the Catera) would produce.

All that being said, yes, the Catera is made by GM.
But it's based on the german-designed Opel.
And many of its weirdities are based on German automotive design, which is often different from american.

So the might have a fuse that *appears* to be labeled 'ALTN', but it refers to something completely different in German.
Or mebbe some idiot in Munich actually DID put install a 30A fuse for an alternator; but I seriously doubt it.

You need to find out what device is served by that fuse, and fix the short circuit.

Hope this helps,
-Rick

[jonnythan]

Good post, Rick, but you confused "amps" for "watts" right there in the middle. I can imagine that it's been a long, long time since a car was produced whose alternator is only capable of 130 watts :)

[rixGAphx]

Originally posted by jonnythan
Good post, Rick, but you confused "amps" for "watts" right there in the middle. I can imagine that it's been a long, long time since a car was produced whose alternator is only capable of 130 watts :) DOH!! :slapself:

I'm :owned: by lack of sleep this morning.

Thanks for the catch!

[jcasemore]

Well, I agree that the output from the alternator would be over 20 amps but...

In quite a few alternators, there is an output and an input. The output is self explanatory, but the input takes power from the battery to power the magnetic field within the alternator. Without the field, the alternator will not produce output.

(I think on the GA it is fuse 49 called 'generator')

Regardless, I would say you have a wiring problem like rix said. Most likely a bare wire somewhere.