Suddenly blows fuse as soon as plugged in why?

Take a test light and hook it up to the battery negative ($10) and check for power on both sides of the fuses with everything turned on. If a fuse has power on one side and not the other it is blown.

Bikes tend to have in-line fuses as well, and sometimes radio's have fuses plugged nto the back of them.

I f you are using the plug and play harness that comes with you truck. Then go throw and just the radio its own power with its own fuse and then ground it to the body of the truck and see if that helps. If it does not help then take the radio out hook it to the battery with a fuse in line and see if it still blows the fuse, if it does then there is something in the radio that is not right.

I have seen this before were the 46 fuse keeps blowing and it is usually after somone has had the radio and heater control out. There should be 2 wire harnesses that plug into the back of the heater control but the 1 will fit the extra plug on the back of the radio and the customer had the heater harness pluged into the radio. Radio worked fine but the rear defogger and a few other heater controls did not and it would blow the 46 fuse as soon as the key is turned on,.

Harman Kardon HK3490 Service Manual luck for you

This radio has a mic check. Turn on radio with out mic plugged in when you plug it in the volume should increase.

Possible causes.

1. Solder or wire in mic cord broken.
2. Bad switch in mic .....Astatic mics are bad for this

Sudden death in vehicle is usually based on something electrical. Check fuses and relays with fuses. Check 1) spark on each plug in turn 2) crank sensor 3) coil 4) cam sensor 5) main relay. Put ignition on position 2 and listen at the open fuel filler pipe for the pre-pump operating. Listen for main pump operation. (If unsure what it is you are listening for remove the fuse for the pump and you nshould notice it being quieter) Check fuel rail for pressure (there is a Schrader 'tire' valve on the fuel rail for pressure testing purposes). If fuel flow is low then this could be blocked fuel filter or tired pump. Finally make sure throttle body is good and clean internally at least and that associated idle air valve is clean and working. With fuel air and spark at the right moment the engine should run. My gut feeling is the crank sensor

It's probably not a fuse. It sounds like your vehicle speed sensor went bad in the transmission. The reason your radio stopped working was because your radio is probably equipped with speed sensitive volume and it requires a speed signal to work.

well if you hear a rattle sound its probably already blown...and the amp could be drawing too much power if the radio shuts off...make sure all your wiring is correct. also if your car is off and you turn it up it will most likely shut off cause the battery cant handle it. but as for the sub i think its blown. good luck

First,
Disconnect any input cables from the amp. Turn down the volume controls and disconnect the speakers. Power back on. If you still blow fuses with nothing hooked up, have the amp fixed.
If the fuse holds, shut down and connect the speakers, leaving the volume controls down. Power up and see if your fuse holds. If you have hum, an output transistor is most likely shorted. If you have no noise, SLOWLY turn up the volume controls and listen for the hum. If all is quiet, turn down the volume controls and connect your input cables and turn the volume back up. Noise? check your cables!
Mister Phil

Here's the overview on fuse blows:

If the fuse blows as soon as you plug the oven in the wall, or when you open the door, the problem is likely with the door switches.

If the fuse blows as soon as you hit START, then it's likely that you have a shorted high-voltage capacitor.

If the fuse blows a few seconds after you hit START, then it's likely that you have an overheating / shorting high-voltage transformer.

If you or a friend decide to work on it, we have *critical* safety, disassembly, troubleshooting info, door switch info, etc. at our site: http://www.microwavecontrol.com