1978 cb400t keeps blowing a fuses.

[apreludem]

today i finally finished with what i was doing to it and managed to get power to it....once the ignition was turned to "on" my lights came on, even the ones in the gauge cluster...then i hear some noise coming from where the electrical stuff is at...and then all power is shut down. i check the fuse box and sure enough the first completely blown....i replace it..try it again and this time i am keeping my eye on it...i noticed some sparks but couldn't tell from where...it looked like they came from the flasher.....what does the flasher do anyways? i have no signal lights on there, in case it has something to do with signal lights. i have to go buy some more fuses now...

 

[killian101]

something is grounding...I had something similar happen. I had a broken bulb in the lens. The metal bits where causing a short. check all the connections...

 

[apreludem]

ill check the headlight since that's the only thing i have on at the moment lol

 

[Catbird]

It's also possible one of the components is drawing too much current. A bulb or a blinker or somesuch that's too big, or out of spec?

 

[Thunderchild]

You're going to have to do some basic, electrical troubleshooting... You really need a schematic/wiring diagram for the bike and at least a cheap Volt/Ohm meter.

Which fuse is blowing? (I know you said the first one... is that the top one?) What all is on the circuit? The wiring diagram will tell you.

Disconnect everything you don't need for the bike to run. Undo the headlight, taillight, idiot lights, etc. Some of the connectors are in the headlight shell.

Turn the key on... Does the fuse still blow with the stuff disconnected? You most likely burned up some insulation in the wiring harness and have a direct short somewhere. That can be a **&^$@# to trace down. Look for burned wires, and use your nose to sniff around to see if anything smells burned.

Nothing obvious burned? Start plugging in connectors -one at a time- and turn your key on. All good? Plug the next connector in. Keep going until you pop your fuse. What's on the circuit that caused the fuse to blow?

There's better ways to do this without popping fuses and possibly causing more damage, but you need to know how to use a meter to check for shorts, etc.

TC

 

[apreludem]

thank you so much .