The Stovebolt Site Forums The Shop Area The Electrical Bay Turn signal fuses keeps blowing!

I am not the most proficient at electrical nor do I really like doing it, so I come to you experts of the elecrical current!

I installed a Painless harness few years back. My signal fuse blew last night, tried another one to make sure it is a continual problem, and the second one blew as soon as I moved the turn signal lever. What is the best way to go about finding the short? Just follow the turn-signal wires till I find it grounding somewheres? How maybe a better understanding of why it blows fuses is better so I know what to look for? (Can you see I'm very lost?) Thanks for the help folks!

Instead of continuing to blow fuses, try installing a light bulb instead of a fuse. I like to solder a couple of wires onto a dash light bulb, and plug that assembly in instead of a fuse. A probe-type test light will do the same thing, plugged into the fuse connection. If the circuit has a major short, the bulb will burn. Disconnect wires until the light goes out, then track that wire down to find your short.
Jerry

I really like the light bulb idea! I have had a similair problem in the past and would do different things to fix the problem, so I thought, then stick another fuse in and it blew. I went through 5 or 6 fuses that time! Thanks for the tips Jerry, I'll give it a go as soon as I can!

Jerry, I usually understand your advice but you have me on this one. How is a light in the fuse holder going to isolate a short to ground? Won't there be current flowing through the bulb whether the system is grounding through the turn signal bulb or grounding from a short?

I was trained to troubleshoot on military aircraft and I prefer to troubleshoot with a meter. I'd determine which side was blowing the fuse, left or right. There you've narrowed it down to two circuits. Disconnect the wires to that side and with your meter check for resistance. If there is significant resistance that circuit is grounding through the bulb. If there is little or no resistance it is shorting to ground.

If there's enough of a short to blow the fuse, there's enough to make a light burn bright when inserted in place of the fuse. If it's in series with another bulb, it burns dim, or not at all. It simply limits the current in the shorted wire low enough to prevent damage while the technician searches for the source of the short. I use a small peanut bulb like is used for dashboard illumination with wires and alligator clips or blade terminals attached so I can plug it in place of the fuse. Once the shorted part or wire is located, the bulb goes out- - - -it loses its ground. This method is convenient when a short must be traced the whole length of a vehicle and meter leads simply aren't long enough to reach both ends of the wire.
Jerry

One of the high school subjects I teach is "Automotive Electrical Systems", so I get this type of question all the time. Simply put, a fuse is in the circuit to protect wires, and prevent fires. When a circuit is designed at the factory, engineers figure how much current a piece of electrical equipment needs in order to operate properly, and they use a wire for that circuit that can carry the current safely. For instance, a heater blower motor might need 15 amps, which would require about a #14 wire, or maybe a #12 to supply the current without overheating. Add a little overload capacity for surges, and you'll probably find a 20 amp fuse in that circuit. If a short happens, the fuse will blow before the current goes high enough to overheat the insulation, melt it, and possibly start a fire. The fuse is NOT there to protect the motor- - - - -if it shorts out, the fuse isn't going to prevent the failure. Once a part fails, or an unintended ground happens like a wire rubs through its insulation against the frame, etc., the fuse prevents a disaster. Fuses are sized to match tne wire they protect- - - -if you install a big fuse to handle an overloaded circuit, the wire becomes the fuse and it will overheat or burn instead of the fuse. Lots of vehicles have burned down because someone bypassed a fuse, or used a too-big one after adding extra accerssories to a circuit with a too-small wire to handle the current draw, then upping the size of the fuse.
Jerry

Thanks Jerry, confirmed most of what I learned in my science classes on electricity. I wish my school had an automotive or shop class. Would have really helped my GPA lol!

Great expalanation of your fault finding ways. used similar tracking down industrial faults with 240v . further to your problem remove one external bulb at a time and check your inline light. possible water in a fitting or faulty globe if not either of those you may have a rub thru . going by your photos it is bolt on possibly loose wire in side remove 2 screws and check
hope that helps regards
andrew

I upgrade my stoplights to LED's so I don't think their the problem. I think its going to be a connection issue withone of them though, I remember that being a probelm when I installd the new harness and had new pigtails for those lights. I'm bout to head out side and get to work on it, since I dont have class today/tonight. Thanks for al the suggestions!

sorry left out in my previous comment > indicator mechanism as your photo shows it is a bolton one have had problems with them before , however you mention as soon as you indicate it blows I think it will be with a external globe