Is there a methodical approach or a device that I can use to find where the short circuit is in the interior instrument light circuit?

At the moment I have no instrucment light and no lighting for all the controls (ie., heating, fan etc..). Each time I put in a new fuse, as soon as I turn on my headlights which activates the instrument lighting, it blows it straight away.

Any ideas? pointers??

TIA

 

wut happens if u put a higher voltage fuse?

 

Haven't tried that yet. I would think that it'll blow that too but I don't wanna risk blowing any of the instruments by using a higher than the stock rating. Don't really know what the real implications are if I use a bigger fuse

 

What else have you installed to the electrical system? The culprit usually resides there.

Regardless, you should always have a multimeter when testing electrical stuff.

 

VERY BAD IDEA! The fuse is there for a reason...to blow up instead of frying your electrical components themselves. Put a bigger fuse on, and you'll do more damage. It's better to find the problem than band-aid it and flirt w/frying it.

 

A hundred and one things!! so ccan be a nightmare as I just don't know where to start looking!

Electricians must have a methodical way to fault finding short ccts..

 

start opening up parts of the circuits.. once the short stops happening, then the short is in the last part you unplugged.

Start with the headlight harness.

 

Could it be a fuse that's got a back up , ie, a fuse in the car and a fuse in the fuse box in the engine bay, if the higher voltage one is blown then the lower voltage won't last long as it's design to blow as a backup. I think thats right anyway.

 

Hehe...if a fuse higher up in the chain blows first, then the lower fuse won't blow because it's not receiving any current.

The best way is to simply eliminate each probable source...one at a time. It sucks. I'm willing to bet a connector is shorting out.

 

 

lol

Johnny 5, alive!

I once had a wicked electrical nightmare in my prelude. I must say, the Helm *really* helped me figure it out. The flowcharts tell you which sensor to test first, and how to test it. It saves a lot of trial and error time, if you ask me. Best money spent!

 

lol, u had to break out the johnny 5, didn't ya?

johnny kick y0 butt, johnny kick y0 face, johnny kick yo **** into outer spaaaace!

 

ohh man i just watched that movie for the first time in many years like 2 weeks ago. hah

 

I loved that movie when I was a kid

 

Can't say how helpful this will be, but this is the basic procedure we use at Bosch -

First, check for any obvious signs of damage on the circuit board and connectors - fried / broken components. If it all looks good then it's time to pull out a circuit diagram and a multimeter. Just follow the schematic, beep testing between known points along the way. In your case you have a short between power and ground, so see if there is anything you can do to isolate single components. ie - temporarily remove a device, or lift a pin from the board. Possible failures - shorted capacitor / diode / transistor / voltage regulator.

For example, if there's a capacitor from power to ground then check to make sure it's doing it's job. A beep test should give a short beep instead of a continuous one like when you have a short if everything's ok.

That's just a really basic start and ideally you'd be doing this out of the car with an external power supply with short circuit protection. If you can't do this, then you could try using a resistor inline (replacing the fuse) with the power supply line to limit the current.

 

Finally! someone posted some useful feedback!!

Thanks man much appreciated..I'll give this a try.

"If you can't do this, then you could try using a resistor inline (replacing the fuse) with the power supply line to limit the current."

Do you mean replace the fuse with a resistor instead? How would you limit the current with a power supply inline?

 

Yes. Instead of Battery -> Fuse -> Circuit you would have Battery -> Resistor -> or even Battery -> Fuse -> Resistor -> Circuit if there's room.

This way, even with a short the most current you would consume will be about 12V / R ( by rearranging V = I*R). For example, if you want to limit to 0.1A max, a 120 Ohm with a power rating of at least 1.2W (P = I*V). Compare this to a 0.1Ohm (short), then the current will be 120A and your power 1440W.

Only do this for testing.

 

Coolio..

V=IxR......Brings back good ol memories.....

 

Ah yes, good 'ol Mr. Ohm and that damm law of his...