Convertible Top Test Wires

[arizonajack]

The shop manual calls for:
1 - A single jumper wire with Alligator clips on each end.
2 - A Y-jumper, with one alligator clip and two spade connectors.

Easy enough to make.

But how long should they be?

[jopizz]

Long enough to go from the relay plugs to the bus bar where the power is. 5 or 6 inches is long enough.

John

[Joe Johnston]

In addition to the jumpers and studying the info in the convertible top manuals, I have also added 2 more test wires which I often use when ever I have an electrical issue.

Get a 50' coil of insulated 10 or 12 gauge wire and cut it in half. One piece gets an alligator clip on each end. This is used to check if there is a good ground at the failing device by attaching one end to the battery ground terminal and the other to the malfunctioning light, motor or whatever. The second piece gets an alligator clip and an inline fuse harness on the other. This is used to supply power by clipping to the battery + terminal and the fused end to hot wire the component.

Quite often the lack of a good ground is all that is wrong, and by first providing a solid ground to the battery, a lot of trouble shooting time can often be saved.

[simplyconnected]

Like, like, LIKE! Joe, you give excellent troubleshooting tips and I totally agree with your advice regarding the ground wire.

There is one more 'trick' in my bag of electrical tools. I put a light bulb in series, in the 'power' wire. When checking a motor or other device, if it has a direct short to ground the bulb will shine at full brilliance. What size bulb? I have used a sealed beam to actually see current as it passes, in the form of light. If the circuit is good a larger motor will show light in variable degrees. At first, the bulb will be bright, then the light will tone down and when the motor stalls the light will be bright again.

Incandescent light bulbs raise their resistance as the heat raises. So when the light is dim, or cold, resistance is low (like the bulb isn't even there). I first saw this 'automatic variable resistor' used in a Motorola tube radio. At first I didn't understand the function. Then I stood in awe at the simplicity, cost and engineering brilliance.

I also use this light when chasing unwanted short circuits that pop fuses: Leave the fuse out, connect the test light to +, then connect the light end to the 'bad' circuit. Let the light shine and start unplugging connectors until the light goes out. Eventually you will get to the short. - Dave

[YellowRose]

Convertible Top Test Wires

I have just added this thread to the Technical Resource Library for all to make future use of. Excellent suggestions...

[Joe Johnston]

I too use another hot wire with a bulb in it!!! Never really understood the chemistry behind it, but found it very useful at times, like working under a dash and only need to see the reflection of a bright light somewhere because there is barely room enough to squeeze into, let alone work.

Simple is always best, and adding a solid ground to the battery is the first thing to do in my book (especially with horns that aren't working well as they often have rusty mountings).

[simplyconnected]

Car manufacturers realized the error of their ways as plastics became more prominent in car content. Now, all bulb sockets have their own ground wire. All the ground wires connect directly to the battery and not through the car body. Yes, the battery is connected to the body but very little current goes through it. Spark plugs still use the engine block for a conductor and so do a few other devices.

Classic cars are notorious for poor connections for headlights, horns, stop and tail lights in both the hot and ground sides.

Regarding the topic of a test wire with a lamp in series; if by accident your alligator clip touches ground as you probe around, it simply shines a light and no harm is done.

I use a sealed beam because it has standard 1/4" stabs. I can either connect using terminal connectors or a spare headlight socket. When the light shines, it's hard to miss and it won't burn up soft trim materials. - Dave

[arizonajack]

In addition to the jumpers and studying the info in the convertible top manuals, I have also added 2 more test wires which I often use when ever I have an electrical issue.

Get a 50' coil of insulated 10 or 12 gauge wire and cut it in half. One piece gets an alligator clip on each end. This is used to check if there is a good ground at the failing device by attaching one end to the battery ground terminal and the other to the malfunctioning light, motor or whatever. The second piece gets an alligator clip and an inline fuse harness on the other. This is used to supply power by clipping to the battery + terminal and the fused end to hot wire the component.

What size fuse?

There is one more 'trick' in my bag of electrical tools. I put a light bulb in series, in the 'power' wire. When checking a motor or other device, if it has a direct short to ground the bulb will shine at full brilliance.

Would a test light with a long wire suffice? Something like this:

http://www.homedepot.com/p/Innova-Combination-Test-Light-Circuit-Tester-EPI3410/206888861

I have a couple like that. I can modify one with a longer wire.

I seem to recall making something like that decades ago when I had my Skyliner but haven't needed that kind of troubleshooting until I got my 66 Conv.

Thanks for all the help.

[simplyconnected]

You shouldn't need a wire any heavier than #12 AWG. If the wire is used in 'free air' you can use a 30-amp fuse. If the wire is under a carpet or bundled with other conductors the fuse size should be no larger than 20-amp because the insulation cannot shed heat (like it can in free air).

The test light shown is NOT a good one for several reasons:
It doesn't present a load,
No voltage range is advertised,
LEDs light in the handle when voltage is present.

Some of my best troubleshooting tools are ones I made from parts hanging around. I have even sacrificed test leads because I needed the wire or the clips, etc. Anyone can always run out and buy expensive test equipment that doesn't work any better than ones you make.

Continuity lights are a good example. Ideal sells a chrome model but the cheap plastic ones are safer to use around hot wires and injury from shock is nonexistent:

A continuity light is simply a flashlight bulb in series with a AA battery and it is used on 'dead' wires (for checking fuses, motor leads, switches or ringing out (identifying) wires in a bundle). Sometimes we use a continuity light WITH a jumper wire for circuits with several switches in series, especially when the circuit has more than one faulty switch.

Meters and LED test lights give false readings because they do not 'load' the circuit and are too sensitive. A larger incandescent lamp works best especially for checking connections. - Dave

[Joe Johnston]

What size fuse?

It depends on the expected load you think you will be dealing with. I change it for the occasion or use a circuit breaker, but a good short will blow them all! For me the primary purpose of the fuse was to keep from burning up the wire when I shorted it out from being clumsy! 12V is quite impressive when it starts sparking under a dash or in the trunk. Long ago I started to slide a piece of rubber hose over the exposed end so I didn't have to be quite so careful getting things in position to work.

[arizonajack]

I have to admit that I'm not getting a mental picture of what you guys are using.

Maybe you can post a picture.

I recall that, when I had my Skyliner, I taped a wire end to a screwdriver and clamped the other end on the battery and was able to poke the relays to operate each top function separately.

If we are talking about something like that, I'm not clear where the light comes in.

I'm good with house wiring but a little challenged when it comes to car wiring.

[simplyconnected]

Ok, and if you touched your screwdriver to ground it would melt.

Now, let's give it a big safety net. All this is in series:
Clamp an alligator clip to the plus terminal of your battery. On that clip is a #14 wire about six feet long or so. On the end of that wire I crimp a stab terminal that fits on a sealed beam (let's say it's an upper beam because they have only two terminals). The other sealed beam terminal has the second crimp terminal on a very long wire.

Let's say I put the sealed beam on my dash so the light is visible from all around the car.

If the end wire touches ground the sealed beam will shine, causing zero damage. Now touch that end wire to your relay coil. The coil will energize before the light shines brightly because the lamp has a lower resistance than the relay coil. You may see a momentary light from the inrush current a coil demands. The point is, you can actually see the amount of current by the intensity of a light bulb.

Now, I have a circuit that keeps popping fuses. I leave the fuse blown, but I put my end wire on the 'bad' circuit causing the light shines brightly. Again, no harm. I start pulling bullet connectors until the light goes out, then follow that circuit to the end as I watch the light.

If you made another 'test light' using a dash light (#57 bulb), that tiny bulb resistance is high and it won't pass enough current to turn on a relay coil. <--This type of test light is commonly used to simply detect the presence of 12 volts when the alligator clip is connected to chassis/ground.

Does that explain it better? - Dave

[arizonajack]

Yes, makes sense to me now.

Thanks.