fuse blows

jethro1978 · Post by **jethro1978** » Fri Apr 13, 2007 11:09 am

68 baja bug that I just completly rewired. I went by the diagrams and by advice from a few people. Looking at the fuse panel from inside the car, the first fuse closest to the drivers side blows everytime I turn the key on. What could cause this problem and how could I fix it? Thanks for any advice.

Post by **Marc** » Fri Apr 13, 2007 12:05 pm

I'd say that the t'signal system is the most common culprit, but since you just rewired the car all bets are off.
Start by disconnecting any wires coming off of the bottom of that fuse. Turn the key on and see which one blows the fuse when reconnected.

MNAirHead · Post by **MNAirHead** » Fri Apr 13, 2007 1:36 pm

I know you'd get tons of notes..

Do you have a continuity tester and/or ohm meter?

MNAirHead · Post by **MNAirHead** » Fri Apr 13, 2007 1:39 pm

Marc..

Are you suggesting that the turn singal commonly gets wired to a dead short?

jethro1978 · Post by **jethro1978** » Fri Apr 13, 2007 2:27 pm

Yes I have an ohm meter. If I try each wire and find the one that is blowing the fuse, what do I do next.

Post by **Marc** » Fri Apr 13, 2007 9:28 pm

MNAirHead wrote:Marc..

Are you suggesting that the turn singal commonly gets wired to a dead short?

No (although that's always a possibility - more often a wire gets pinched to ground up at the switch). There could just as easily be a short at the master cylinder stoplight/warning light switches or something wrong with the wiper circuit (like components adrift inside from a broken park switch). Even the horn circuit could have a short. On the late 4-way flasher setup the hazard switch itself sometimes comes apart internally creating a dead short, and on the compound-relay setup used in `66-`68 the flasher box itself has much more to go wrong. First step in troubleshooting is to identify the faulty system.

MNAirHead · Post by **MNAirHead** » Fri Apr 13, 2007 9:36 pm

Marc.. (or someone smarter)

Would you suggest a continuity tester vs ohm meter..

Meter Use...

If you have an on you VOM meter.. you can switch to Ohms (.. or the diode check setting)..

Now cross the 2 leads.. you'll notice the screen changes (digital and/or analog).. this shows that the 2 leads are connecting.

You can use this setting to isolate individual circuits or pieces of wire or connectors that are connecting directly to ground.

Your notation of an instantly burning fuse hints toward one of the wires (connectors etc) directly touching the "ground" ..

Your car does not have to be turned on for this to work.. you may need to have a battery in the car to complete the circuit.

NOTE.. look for burnt wires.. some times they'll get red hot with a direct short and melt the wire housing..

T.

Post by **Marc** » Sat Apr 14, 2007 9:41 am

MNAirHead wrote:...you may need to have a battery in the car to complete the circuit...

Never connect the probes of an ohmmeter (or continuity checker) to a live circuit. These devices use their own small internal battery and subjecting them to 12VDC could burn them out.
By the same token, if you're ever inclined to use the ammeter function of a multimeter to locate an excessive current draw you should be certain that the maximum potential current is within the safe range for that meter. A maximum of 10A is typical - if you're lucky, there's an internal fuse but some meters don't have that and will be instantly and permanently fried.

It's hard to get into much trouble with a test light. It can't give you exact readings but is still quite useful. You can even use one for fault isolation by connecting it across a fuse terminal (with the fuse removed) - the circuit will receive power through the testlamp filament which will burn brightly in the case of a dead short to ground...lift leads one at a time until the light goes out and you've found it.