Hi, I have only used my CA 740C a few times and the fuse blows, I placed another fuse in and that blew as well. Haven't a clue why this might be happening can you help please? Thanks

what do you do when the fuse blows, and which fuse blows

50amp only clue and you dont have the book, the FSM.
nor access to alldata.com?
if you did youd, not be asking right?
my guess is that fuse is in the mains box under hood..
and is a real fuse and not a circuit breaker found elsewhere....????
old car, and can be anything this old.
sounds like fuse #33 in the main box blew. and feeds the white wire main.
USA car? ABS opted? A/C opted. sure.
top cause, shorted alternator, so take off that big wire from alternator
and see if fuse blows now. (do so with battery neg lug removed
the remove alt big wire and tape it all up, so it can touch metal.
then put back battery Neg lug, and last the fuse.

the whtte feed goes vast places and runs whole sections of
the cab fuse boxes and power windows.

if the Alt is good.
then you must start dropping all white wire loads.
if it still blows, the harness is shorted.
I personally just uses a temporary circuit breaker in place of the
50 amp to find the short and an ampclamp DC ammeter.
fast.
login to alldata.com and follow the big white wire.

Did you clean out the lint filter at the front, heat is the enemy. Clean out all lint from front, if you are handy, get around back and remove all lint and dust by blowing compressed air.

may be waterlogged. internal seal failed and its shorting out..

there is a short somewhere.i had that problem.there were some wires melted together.

I’m happy to help further over the phone at https://www.6ya.com/expert/kenneth_3efc1f8510674f04

Have you used 2A SLOW BLOW fuse? This type of fuses usually are ceramic type and are very different with the glass type ones. The glass type fuses are (more or less) fast blow. Although the best solution is to find SLOW BLOW fuses like this, in case it's very difficult you can use 3A fast blow fuse also.

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you have a dead short on the ACC wire (red and gray wire i believe).
Disconnect each component one be one until fuse's stop blowing or use a meter and check for grounded power wires

Are you replacing the wires along with the fuse? It is important to change the wires too as they are usually the cause for the fuse blowing. Be sure and get the fuse kit that includes the wires.

Is your water too hot? Hot water is fine but too hot of water can cause the fuse to blow over time. The temp should be somewhere around 120 F. Anything over 130 F is way too hot. I personally don't use a long high steam final rinse or high heat because over time the steam and cause the electronics to short as steam and moisture can get into the keyboard and inside panel.

Maybe the audio amplifiers IC are in short circuit or the alimentation board are damaged

You should repleace the old transformer with the new one