my illum fuse keeps blowing but its only when i have my lights on and rev it kind of high when driven but last time it did it at lower rpm but i had the radio a little loud can it because i have a s4 alternator in a s5 car and it is the fuse that make the dash lights work and tail lights

 

i'd bet the voltage regulator is getting quite a work out. Check to see your volts during a good rev.

Fuses usually blow when too much current is drawn through. You might be trying to push too much with high voltages.

 

what else can it be

 

Yeah I would be checking the volatge output from the alt.

Also you will want to check the switch, it might be burning out and if your alt is very weak (old) at lower RPM it might be failing as well.

 

how you do you check the volatge output

 

use a multi meter.

Set it to volts.

While running disconnect the negitive battery terminal (should still run - this isnt' a must but an easy way to check if your alt is doing it's job)

Place the red probe on the + wire terminal. Black on the negitive wire.

have someone rev the car and watch the volts.

This might not be the best and "truest" but it'll give you a good idea of what's going on with your charging system.

 

EEEEEKKKK NNNNNOOOOOO> DON"T DO THAT!!!!!

That is a great way to spike the whole electrical system and smoke the alt and ECUs!!!!!

Use an inductive amp tester if you need to test an alt. The battery acts as a capacitor for the whole electrcial system of the car. Disconnecting it while running removes all protection against voltage spikes as well as the regulator in the alt see the loss of capcitance as a need to charge the battery spiking up the alts output.

Bad bad bad bad bad bad....

The electrical system and alts on these cars are not a cheapo GM from the 70's.

 

what might be making the fuse blow

 

im having the same problem, and if your alls ideas dont work im gunna run my own wires to the bulds and use a silinoid to an on/off switch to make my park lights and instrument panel light up. so if you have anymore ideas please post. i am now goin out to check the switch.