Fuse blowing

[wacc]

I have a 78 VB SL 3.3ltr sedan. It has started blowing the instrument fuse. When the fuse blows the red battery light comes on and stays on. Anyone have an idea what may be causing the short?
Bill C

 

[Brett_jjj]

You can sometimes find an intermittent short in wiring pretty easily by using a little trick with a radio, get a portable radio, set it so its not on any station and turn the volume right up so its hissing etc, replace the blown fuse, turn the key on and/or switch the circuit involved on so the circuit is powered up, and start working your way along the wiring wiggling and moving it, start from the switch or fuse box or wherever, and you should hear the radio crackle heaps as the wire that is shorting out is moved.

 

[Nut Kracker]

Does the fuse blow as soon as you replace it, as soon as you turn the lights on, or randomly?

 

[Nut Kracker]

Is there anything else on that circuit? Factory or after market?
What size fuse are you using?
Being a VB, I'm assuming it's a 3AG glass fuse.
Does the fuse blow with the engine off, running, or both?
Are you having any other trouble with any other fuses blowing?
How's the alternator voltage output?

Sorry for all the questions, but we need to know all the facts.

 

[wacc]

Thanks guys. The fuse that is blowing is for the instruments, it is a 5A ceramic. The fuse does not blow straight away but takes a few minutes so guess it is not a dead short. When it blows the instruments (powered ones) needles go back to 0 but the battery charge light comes on and stays on. Vehicle still operates Ok with the exception of the gauges.

 

[Nut Kracker]

May be look at the alternator/regulator voltage output.
With the car running, put a volt meter across the battery terminals, see what the voltage is and get back to us.

 

[wacc]

alternator voltage is running at 13.9 at the battery