Okay, so I'm trying to mount a dome light inside my hood. I spliced it in to my aftermarket tach, tried to test it by putting the end of the wire to the PDT, and that's when things got bad.
The Wire connector (See Below) started smokin. It's one of those orange cap things that twist the two wires together inside. The length of wire between the connector and the light melted. Naturally, the dome light was also smoking pretty good. Anyone know what I might have done wrong? There doesn't appear to be any damaged components on the other end of the connection.
I've never had any problem wiring things directly to a power source.

PDT------------------------------Splice-------------------------------Tach



I can't get this next part of the diagram to line up but it should be coming out of the SPLICE.

|
|
|
Wire Connector (Smokin)
|
|Melted Wire
|
Light (Smokin Lots) -------------GROUND

Also, for everyone who replied to my last post about re-doing the electrical system I had going, Thanks. I'm working on wiring everything to an auxillary fuse box powerd by the PDT. It looks real nice. Naturally after this incident, I'm hesitant to make that final connection b/w the PDT and the fuses.

Thanks all.

 

Doesn't your truck have a light under the hood?

 

I wish. It's a 1995 F150. *shrug*

 

That clears up alot.

What kind of a light are you hooking up? Manual switch/Mercury switch/how many watts?

This isn't a test, I'm just wondering. It sounds like the Tach and the downstream components don't like the light you chose. You will probably have better luck on a different line, and when you do it go: Tap>fuseable link>light.

 

I just grabbed a cheap dome light from Napa. I would imagine it is a pretty low watt setup. The Tachometer is also a generic Auto Zone tach. Not sure how many watts it uses. I can see, however, that if the Tach was drawing twice the Watts, that could cause problems with the Dome light. I'll go ahead and run each of them with separate wires to separate fuses in my box. Thanks

 

The reason is simple... a direct short to ground through the light fixture.

Rule #1: ALWAYS include a fuse in-line... especially when testing!


What was the location of the Light fixture when you were testing?

Was it "sitting around" under the hood on something metal?

Was it mounted to the hood already?

Is it possible in mounting it to the hood (if it is/was) you shorted the "+" supply to the hood.

Is it the correct bulb and is it inserted correctly?

Did the lamp illuminate during testing?

It has nothing to do with the Tach. and this incident should not have done any damage to it.

The PDT is the correct place to connect to when possible but always follow rule #1.



Good_luck... XLT_D

 

The light was mounted to the hood. It has a metal plate which attaches to the hood with sheet metal screws. The plate has a hole in it which the wires go through. Then there is a plastic cover that attaches to the plate. So the wires go through the hole in the metal which has a rubber grommet, then the wires exit through a pre-existing hole in the sheet metal and down to the tach splice. I don't see anywhere that the wires touch metal except where they connect to the light bulb or whatever. How would I short the + to the hood? Wire to sheetmetal? And yes, the light worked fine in preliminary testing where I put it right up to the battery out of the box.

 

So I replaced the melted wire and tried again. Same results except this time it blew a 3 Amp fuse rather than create smoke. One thing I did notice is that the positive line from the PDT attaches to the metal plate which is attached to the hood. Is this what's causing the problem? I.e. Shorting the +. What if I put some cardboard between the metal plate and the hood so they weren't touching? Comments? Again, thanks all!

 

Hello,
I am not an expert and besides I think you've figured this out already... but just in case here is what I would do:
1. Fuse is always a good idea;
2. You pretty much connect your *plus* to the PDT. Why did you splice instead of putting a separate wire? I would try this...
3. I would remove the bulb to see if there is a short in the holder then put the bulb in... Maybe the bulp is broken?
Alex.

 

UC,


That's it, the metal plate is intended to be grounded via it's mounting screws.


This way it could be grounded through the fixture for mounting it to the chassis, (and requiring only one wire to "+").


If it worked before mounting that proves you have an issue with the mounting.


Do you have an Ohmmeter? This can test for shorts.
It really is a simple problem to fix if you have one.

Good_Luck...XLT_D

.

 

urbancowboy
it sounds like the light is wired or marked wrong. the + wire never attaches to a grounded surface. try your fuse with the other wire out of the light
and cut off the wire hooked to the mounting plate.