Is it a good practice to wire a strobe light (beacon on top truck) with the negative wire grounded to the headache rack of a truck to complete the power circuit? No other negative cable was used.
A while back, the strobe light caused a very bad short which paralyzed the truck. Even with the strobe light switch at off position. After blowing a few fuses, heavy duty mechanic did one more test by replacing the blown fuse with a metal piece. The metal piece became instantly burning red. So he cut the wire of the strobe light switch behind the driving column. Problem was solved and truck was running again.
Working on the strobe light today, I am thinking if the strobe light had been wired differently, would this problem happened? Is this a common way to wire a strobe light?
Any direct current automotive accessory (dc) should, in theory, operate grounded to the frame or body. Some cabs are not grounded real well anymore. Fords used to have a real 'floating ground' problem.
Make sure the vehicle is negative ground. The only reason a 'jumped' fuse glows red is because of a direct short.
Just to make sure, I'd run a separate ground wire if possible.
The stobe light was originally installed at the Ford Dealership. They outfitted a lot of trucks with strobe lights over the years. I suspect they have a good procedure in place.
I was just curious about this method of wiring with one positive (+) cable to power source, One negative (-) to the frame, 2 cables total.
> Make sure the vehicle is negative ground.
I haven't encountered a positive ground vehicle since I sold my '51 Dodge pickup in the mid-90s, and it was 6-volt. Are there any vehicles made now that aren't negative ground?
Sounds like it was the hot side that had a direct short to ground, not the ground wire itself causing the problem, someplace between the switch / fuse, the power supply (hot) wire to the strobe was grounded to chassis.
SHG
I never liked the strobes because of the radio interference and messing with the sensor on a rotating laser. LED's are much better. I have left my led mini lightbar on for 8 hours straight without draining the battery.
James
I think Shelby is right... you have a short on your hot side, between the battery and the light. It is not a ground problem.... even if one exists.
N
> Is it a good practice to wire a strobe light (beacon on top truck) with the negative wire grounded to the headache rack of a truck to complete the power circuit? No other negative cable was used.
>
> A while back, the strobe light caused a very bad short which paralyzed the truck. Even with the strobe light switch at off position. After blowing a few fuses, heavy duty mechanic did one more test by replacing the blown fuse with a metal piece. The metal piece became instantly burning red. So he cut the wire of the strobe light switch behind the driving column. Problem was solved and truck was running again.
>
> Working on the strobe light today, I am thinking if the strobe light had been wired differently, would this problem happened? Is this a common way to wire a strobe light?
You need a new mechanic first - the one you have who put a solid strip in for a fuse is a dangerous idiot. What he did could have burned up a wiring harness or any number of other things.
Shelby is correct. A short circuit is, by definition, a circuit that is grounded "short" of its intended target, in this case, the strobe.
The most likely problem with grounding the strobe through the chassis is an open circuit. The strobe wouldn't work but your truck wouldn't be disabled.
You said the problem existed even with the switch turned off so my first inclination is, either the switch is defective or the wiring from the fuse panel to the switch is shorted to the chassis.
Or maybe he is a very good mechanic who knew the limits of the machine when performed the test? Don't ask me, I don't know. Myself, I know very little about automotive. All I know is that at no charge, that mechanic got the truck running and kept me surveying/working.
About the present situation, here's the solution I came up with for the remainder of the truck's life: I ended up cutting the power cable on one of my old Trimble 5 pin lemo cable and hooked that chunk on the strobe light, red on red and black on black. The rubber plug-in is protected from the elements under the strobe light mount. When I need the strobe light, I plug in the cable directly to the external battery or to the power source (lighter).
Thanks for all comments, very informative.
Edit: by the way, the mentioned-fuse was a heavy one under the hood, not one of the lighter ones inside the cab in the panel.
