amp fuse

If an amp's original fuse is 35a is it ok to put a 40a fuse in it to replace the original?

Fuses are cheap.  Amp repair is not.  If you overfuse any electronic device, the device becomes the new fuse.  If the amp had a 35 originally and you are blowing it, chences are you have it improperly installed.

Ditto.
It might be (and probably is?), but if it isn't....

Well I'm getting it used, and the previous owner blew the 35a fuse and put in a 40. But I should put in a 35a fuse, will that work best?

Correct me please if this isn't right.

If an amp blows a fuse, isn't it more likely to shut down due to thermal overload before blowing the fuse?

Is it typical for an amp to blow a fuse other than a dead short elsewhere?

Seems to me that if an amp blows a fuse, there is a good chance of internal damage already, in which case you would NOT want to put a bigger fuse in the first place.

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Still learning

Kraco

Wiring an amp into too low of an ohm load is the most common cause for blowing fuses.  If an amp is putting out 400 watts when properly installed, and then you add 2 more speakers, the amp will try and produce 600 watts.  Thus requiring more current from the battery.

The amp is stable down to two home, it will be push 95 watts through two channels at four ohms

knotdrummer88,

In addition to what "I am an idiot" has already expounded on, remember that the manufacturer used a 35A fuse for a reason. Don't take a chance on using a higher rated fuse. If you do and the amp gets damaged, you are out the money for the used amp and now you have to buy a new one. This would defeat the purpose of buying a used amp. In addition, see if you can test it prior to purchase. If your vehicle is already prepped (i.e. all wires are ready - Power, Ground, Remote, Speakers), then the only thing left is to install it and test it for functionality. This should not take long to do and that way, you can be confident that it will meet your requirements. If it doesn't work, walk away.

Good Luck and Have Fun.

Oh yeah of course ill test it man, and I talked to the guy today, and he said he has a 35 in it, so I must have misunderstood him before, but thanks a lot for the insight everyone!

That Idiot put it well....

Fuses act faster than thermal shutdowns and sensing (though a fuse itself is thermal).
Should there be a short or overload at the output, the fuse may blow faster than output protection, hence saving costly repairs.


Having said that - and without specific amp experience - it is rare for a fuse to be critically matched to a load.
They are only available in discrete values so a near-enough choice has to be made (eg, blade fuses above 30A are available in 10A increments).
Besides, the max tolerable amperage may depend on the voltage. EG - a 500W (input) amp is 35A at 14.4V and 40A at 12.5V (assuming it is a constant power device - eg internal dc-dc conversion as per a single channel 1-Ohm output above ~200W).

Although a 40A fuse is only 14% larger than a 35A, the transmitted power may be 30% higher. A 15% overload may be tolerable, but 30% may not (ie, 30% more heat).

For wiring (aka distribution), the larger 40A probably won't matter - a wire's rating for a particular current is based on a certain packaging and allowable voltage drop - whether for performance or for limited heating. If for performance, the 14% higher fuse meaning 30% more heat may not matter.

But circuits and component may be different.


In your case, I'd try a 30A fuse if they are available.
If they consistently blow, then consider a 40A fuse if the 35A isn't available.
Or short the fuse and use inline parallel 20 & 15A fuses etc....

As before, it may mean the amp is damaged in overload cases. Or not.

You could try an overload and find out....
(Not that that tests other failure modes.)