Circuit Tester 101

Still learning the basics of testing the electronics so please forgive the dumb question:
Im running into a bunch of issues with the electrical system and was using a circuit tester on various parts of system trying to check for shorts.
Placing the alligator clip of the circuit tester on the engine block and then touching the tester's tip to any metal part of the bike (handle bar, exposed frame, etc.) will light the tester's bulb when the key is in and switched to the on position.

This is not good right??

 

If you have the tester on the continuity or resistance range, (Testing for a circuit) this is correct. All the metal parts of the bike are connected together, just like in a car, which has a negative ground.

If you have your tester on the voltage range and you are measuring a difference in potential between the engine and the frame, this would be wrong.

Switch off the ignition and test again.

 

If you're using a "circuit tester" consisting of a clip, a probe and a light bulb, you're not going to get far.

Markie's response assumes you are using a meter. If not, you need to get one, those "circuit testers" are not a very good diagnostic tool.

 

First make sure the heavy wire from the negative side of the battery to the engine is clean and tight, so you have a good ground to start with. If that's a poor connection, all your testing will be a waste of time.

 

I do too much ASS -U-ME ing!

+1 on the multimeter - they are quite cheap and very helpful.

 

If you are using one similar to the Lisle# 26200:

...then this would actually be a continuity tester. They work okay, but as other have stated, a digital multimeter would be the best tool for the job. A stab-style continuity tester can be differentiated from stab-style circuit tester by noting whether it has a battery or not. Another way to tell is to touch the alligator lead to the pointy end. If it lights up, it is a continuity tester (assuming the battery is good).

 

Thanks! I will make sure to pick up a digital multimeter ASAP. I was a little concerned when using the stab style circuit tester (I'm pretty sure its the no battery kind but have to go back to garage on other side of town to check now.) because in my thinking the body of bike is used as ground and should not be "energized" when tested with a simple circuit tester that has no battery, (this may be the wrong analogy, but itsn't that like trying to test for a circuit solely on a ground black wire?) I will find out if it is a continuity style tester w/battery or not to be sure.

 

It has to be the battery type hence the name "continuity" tester. That's different from a test light. All that device does is check the run of a circuit from point A to point B by shooting some voltage from its source. If you are going from ground to ground and the light bulb illuminates, it is simply indicating you have continuity of some sort between point A (the engine block) and point B (wherever you touch and the light illuminates). If you're gonna use this kind of device you need a simple test light which requires a ground and a power source to illuminate the bulb. They are quite handy for simple diagnostics like checking to make sure power is getting to your brake or tail light socket, for example. On any equipment with either a computer or other sensitive electronics they are a big mobile electronics 101 "no-no."

I agree that a digital multimeter (DMM) is the way to go for most general diagnostics because there is no way with a test light to tell the values of a circuit with one. Sure, the light may come on but does that mean a circuit is actually energized with the voltage and/or current it is supposed to have? No way to tell.

A continuity tester can be a valuable too to quick-check a circuit with the key in the off position for sure on an older bike like these -- ones without all the modern computers and sensors. But the DMM is really the way to go since you can check resistance too. I would be lost without mine.

 

You won't need a meter to tell you the fuse box is crumbling. Start there, meter or not.

If that other thing is a battery-op light-up toy, just pitch it, honest. Breaker's advice in regard to modern electronics is spot-on, plus even with a primitive system like ours, it doesn't give you any information of any value, as it brings its own "juice." Dumpster food. Donate it to a Cub Scout troop.

 

Thanks for the 101! I'll dump the tester Toy and get a real multimeter to test with from now on. Now to figure out why the dam headlight comes on only when I hold the clutch in. Time to start another post. Forgive me XJ Wizards!

 

I read through your other post on the safety relay/solenoid. My initial thought when I read that your headlight only comes on when the clutch lever is engaged was your ground path for the headlight was shorted. After reading the other post, it sounds more like your whole wiring harness is butchered... and badly.

Did you get those wiring diagrams that were offered to you? If not, try here and here. It sounds to me like the PO yanked out a large portion of your grounding system. You're going to have to go through the entire system and make sure everything is hooked up correctly. And that means checking all the grounds, too.

 

Hey Don, Thank you so much for the reply.I did get the wiring diagrams and use the one from the clymers manual as well. Yeah the wiring is looking pretty mangled , probably took years for it to reach its current sad state. What is weird is that the despite all the hacks and butchering it worked fine up until recently.

I changed the levers (both the clutch and brake) and noticed that was when the problems really began with the light only coming on with the clutch lever in(actually the light comes on once the bike kicks over and starts, which isnt easy right now). So I figured I must have pulled somehting apart in the harness while threading the new choke cable through (i replaced that at the same time) but nothing looks moved at all and I used the trick of attaching a string and tape so that the new cable followed the old one exactly through the body.

Interestingly, it seems like when the clutch is in the light stays on and the starting system builds some sort of charge so that the start button actually engages the starter. Have you ever heard of this. It will run for a minute trying to kick over and then stop suddenly, with no juice. I ll hold the clutch in for a few seconds and then try it again and sure enough the starter button works. I may go insane

 

It's probably using the clutch cable as a ground path. Try taking a set of jumper cables and--using the black lead--clamp one end to the handlebar and the other to the battery's negative terminal. Then see if all your electrical anomalies disappear. If they do you definitely have a grounding issue.