Keep blowing Fuses! Help *see diagram*

ok I keep blowing fuses and I dont know why. The fuse is a 8A 250V in-line glass fuse used for my undercar kit. Key piece of information, I had the kit wired as shown in the diagram for about a week no problem....then it rained out and the ground was wet one night when I had them on, first time the fuse blew. Then a couple days later (without touching the wiring) I replaced the fuse and it blew instantly.

this is the setup

http://www.mountaincable.net/~jtdemelo/diagram.jpg

the fuse in red indicates the fuse that is blowing.

Now the only thing that I guess on when I installed it had to do with the switch. As you can see, the switch has 3 wires, (one is black, the other 2 are red)....would it matter if I switched the wire that was suppose to go to the batter with the one that went to the transformer and vis versa?

I checked all the wires under the car, no plit or exposed wires.....

**note** everything is INSIDE the vechile except for the bulbs themselves, the transformer as well as the connections for it as inside the vechile

I put a multimeter to it, checked the volts comming from the switch to the transformer, read 12.5volts with vechile off, switch on....but then I tried to read the amps, same spot again (where the inline fuse is, just not connected) and I couldnt get a reading...I tried all settings, 10a, 200mA, 20mA, 2mA....

on 10a for example, the reading would just jump to "1" instantly and the tips would get VERY hot, VERY fast...too much amperage I'm guessing for it to reaD? :confused:

any ideas? :(

Have you checked the wiring in the switch and the switch itself?

its a simple switch, not much to look at, but out of the 3 wires, there is no splits and they arent touching each other...is there something else I should look at?

its a simple switch, not much to look at, but out of the 3 wires, there is no splits and they arent touching each other...is there something else I should look at?


You'll probably have to go through the process of illimination and determine what component is popping the fuse. The fuse is protecting the input to the transformer (primary windings). The short could be possibly be at the output of the transformer (secondaries). Try disconnecting the wires on the output of the transformer. Then put the 8a fuse back in and see if it pops. If it pops your transformer could be defective due to the moisture you encountered. If the fuse holds then it is either the output secondary part of the transformer or a heck of a load or short in the wiring underneath the car to the lamps or one or more of the lamps themselves.

To test the switch you can either ohm it out across the normally open or closed contacts. With the output of the transformer disconnected you can activate the switch and then measure the voltage at the input of the transformer. If its correct then the switch is good. Of course make sure you've got a good fuse in and this is assuming the short is after the transformer. It a relatively simple circuit. Good luck!

**UPDATE**

I disconnected the 2 output wires from the transformer to the bulbs, so it basically looks like this now...

http://www.mountaincable.net/~jtdemelo/diagram2.jpg

and the fuse still blew!

Do you have a good ground? I almost bet its that switch.

Do you have a good ground? I almost bet its that switch.


It could be because at this point he can't rule it out. What we do know is that it is not the wiring after the transformer or any of the lamps since he disconnected the output of the ballast transformer and the fuse still popped. Which is good news in a sense. Based on his simple schematics all that left is wiring before the transformer input, the switch, the 8 amp fuseholder itself or the primaries of the ballast transformer.

He could disconnect the B+ supply at the battery or pull the first fuse by the battery and leave the input to the transformer disconnected. Then take a multimeter in ohms position and probe to ground at the transformer input leads back to the switch and see if it reads a short. Probe each contact on the switch (red wires) to ground in the process too. Thats one heck of a short or load to pop an 8 amp fuse.

Does he know if the switch is wired correctly?

well I looked into seeing if the switch was wired correctly, and I was told it didnt matter what red wire went to the battery, and to the transformer. Either one would work....

now keep in mind, the setup you see there, I was running it like that with no problems for about a week

I believe its the transformer...I'm getting about 3.5 ohms from the transformer

my buddy at the shop I bought the kit is hopefully gonna get me a replacement transformer...hopefully that solves the problem

well I looked into seeing if the switch was wired correctly, and I was told it didnt matter what red wire went to the battery, and to the transformer. Either one would work....

now keep in mind, the setup you see there, I was running it like that with no problems for about a week

I believe its the transformer...I'm getting about 3.5 ohms from the transformer

I agree you have a defective ballast transformer because its in a F-Lamp circuit and is of the variety that is loosely coupled between the primaries and secondaries for the purpose of limiting the amount of current the secondaries supply. The water/moisture probably took it out. It could have been worse and you could have 4 blown lamps.

The actual purpose of the transformer is for current limiting purposes and to prevent the lamps from self-destructing when they ionize.

Good luck in your repairs!