The 25+ - Using a continuity tester, test light, volt-ohm meter.

#24. How do I use a continuity tester? a test light? a volt-ohm meter?

I hate to tell you to read the instructions...but that would be a good place to start. Each one tests for something related but different and will give you different information.

A continuity tester checks to see if two things (two parts, two spots on a circuit) are electrically connected. So, if you touch one probe of the continuity tester to one end of a wire and the other probe to the other end of the wire, the tester should “buzz” (the usual audible output of those units). That tells you the wire is “continuous”. If the tester doesn’t buzz, the wire must have a break in it...no wonder the circuit didn’t work!

So, a continuity tester will tell you if the two things are connected, but it won’t tell you how well they are connected, whether they are connected grounds as opposed to connected power leads or even whether or not there is power there at all. That makes a continuity test great for making sure that two things are NOT connected (such as by a short between them) - no buzz, no connection, no short. It is also a quick way to test whether or not a switch is open/closed, whether a relay is making/breaking, etc. It will tell you connected or not connected, period.

A test light, on the other hand is specifically testing for “hot” power. Usually it will have a clip that gets attached to a ground and a pointed probe that is touched to various spots in the circuit. If the light comes on, that spot is hot. But again, it doesn’t tell you anything else that may be going on or the quality of the circuit or the hot power. In fact, I have seen cases where a test light gave very false information by being an additional “leg” in the circuit, thereby changing the circuit and messing up the test. A pretest diagram might help prevent this type error, too.

So, a test light checks for a hot circuit, which makes it very good for assuring that the power got turned OFF before clipping a wire by mistake, for example. It can also assure you that the power is being turned on/off by a switch or relay. But don’t ask it to tell you the quality of that hot power.

Which brings us to a Volt-Ohm meter, which can tell us voltage and resistance (hence the name!) This allows a much better diagnosis of a circuit because we can get more information. Compare the volt meter feature alone to the continuity tests or test light checks that I described, above. A voltage measurement can better tell the quality of the hot power at any point in a circuit, either compared to ground (zero voltage) as as a voltage drop across a component. But I don’t want to get into details here. This is a case where you must read the directions. They should tell you not only how to use the meter but should also give you some examples to help interpret results. Happy testing!

Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com

The 25+ - The Problem with Bench Testing

#23. Why is it that some switches/loads/circuits can’t be “bench” tested? Why do they have to be installed in the car and tested with the car ON and running?

Truth be known, anything can be bench tested IF the test accurately and completely represents the real world circuit that will be present in the car, in use. But that’s a big “IF”.

When was the last time you prepared to do a bench test by drawing out the circuit diagram? When did you double check you power supply to make sure it was sufficient? And worse yet, when was the last time you started to do a bench test with “live” power and fried a component? These are just a few of the issues with bench testing.

Even when testing is being done in the car, a lot of people figure that their battery is fully charged (even though the car hasn’t been started once during the last two weeks of testing). They put a trickle charger on the battery, so it must be good. Or they are just using the battery charger all by itself to do the testing, never considering the voltage and amperage output versus the parts need. A part doesn’t work quite right and they assume the worst.

We even see a certain group of customers who must have gotten burnt (pun intended) in the past, who have to - by their genetic makeup - bench test every single thing that they buy. Invariably, the part fails their bench test and they have been “burnt again”, never realizing that it is their testing that is the problem. Still another small group will be doing a major electrical installation and feel the need to connect power and test the last circuit that they installed, although they are still far from completion. This is a open invitation to problems - connecting power to an entire system while only part of it is done.

So, go ahead and bench test (because we know that you will anyway), but do it wisely. And if something doesn’t work right, please, question your testing before you call and blame the part for being faulty.

Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com

The 25+ - How do I check a relay?

Moving into some more general questions:

#22. How do I check a relay to make sure that it’s not bad?

Good relays very seldom go bad, although poor diagnosticians seem to often point to a relay as a last ditch answer for another electrical problem. Almost all relays “click” when they turn ON and again when they turn OFF. If you activate the switch that controls the relay and you can hear the relay “click”, then the odds are good that the relay is good. If there’s no “click”, the relay could be bad, or it just might not be receiving the electrical signal. It’s best to pull the relay out of the circuit and do a bench test.

Both Single-Poll/Single-Throw and Single-Poll/Double-Throw relays should be marked with terminals 85, 86, 87 and 30. Ground terminal 86 and connect terminal 85 to +12 vdc power. The relay should click ON. Disconnect terminal 85 and the relay should click OFF. If it does that but you’re still suspicious of it working right, connect terminals 30 and 87 to a continuity tester and repeat. When terminal 85 is energized, 30 and 87 should be connected (continuous). When terminal 85 is de-energized, 30 and 87 should be disconnected (open). Cycle the relay on and off a few times until you are sure that it is good or bad. This test will check for 99.44% of possible relay malfunctions.

Better yet, let’s be Mr. Practical and leave the bench test for later when we have more time. Instead, just put a new relay in the circuit (you do have spare relays, don’t you?). If that cures the problem, throw the old relay away and go on about your business. If the problem still exists after changing relays, you need to look beyond the relay for the source of the problem.

Steve Watson, Watson's StreetWorks,  http://www.watsons-streetworks.com

The 25+, "Brake LIght Override"

Continuing on the subject of Taillights and Brake LIghts...

#21. What is “brake light override” circuitry and why do I need it?

Before I explain what it is, let me say that you may or may not need it. That will depend upon the type of tail lights you have and how they are set up.

Brake light override is what happens when the brake light cancels out the turn signal - the brake light “overrides” the turn signal so that the turn signal is no longer visible. And this only happens if the brake light and turn signal functions are being performed by the same bulb/filament, such as when just one #1157 style bulb is being used for tail light, brake light and turn signal. An 1157 has just two filaments inside - one is a lower brightness filament which is for the tail lights, the second is brighter and is both the turn signal and brake light. To prevent override, the car’s turn signal mechanism (usually inside the steering column) turns off the brake light feed to a light whenever the turn signal is turned ON. So if the left turn signal is flashing, the right brake light will still work but the left brake light does not - right side brake light, left side turn signal (and visa versa when the right turn signal is ON).

A car that has separate bulbs or filaments for each function, like Beetles and many foreign cars, and newer US cars and trucks, too, will not need, and therefore will not have, the override circuitry. The easiest way to spot these cars is if they have amber rear turn signals - a dead giveaway that they are separate from the brake lights which must, by law, be red. However, some cars have separate red turn signals. You just have to double check to see which you have.

But this was all figured out by the car manufacturer when they designed the car. The problem comes up when we decide to add turn signals to a car that didn’t originally have them or, more often the case, when we try to change tail lights. 

If your car had separate turn signals before and now you are trying to go to tail lights that require brake light override circuitry, you have a challenge awaiting you. It’s best to know what you have to begin with before you go buying new tail lights and get into trouble. Tell the sales person what you have and figure out whether the new units will work “as-is” or whether additional parts will be needed (such as our Turn Signal Relay Pack which has brake light override circuitry built into it). In worst case scenarios, however, the car has been designed with a special flasher, burnt-out-bulb sensors and god-only-knows-what other special “features” that will make changing tail lights a living hell. Don’t try it and blame the tail light manufacturer if you haven’t done your homework up front.

Going the other way - from a car that had override circuitry to separate brake lights and turn signals - requires bypassing the original turn signal mechanism or at least not running the brake light feed through that mechanism. A little extra work, but nothing like what I talked about above.

Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com

The 25+, "LED Taillights"

It's time to start talking about Taillights and Turn Signals...

#20. I’ve replaced my tail lights with LED units and they don’t work right. What’s wrong?

Wow! What a loaded question. There are so many different things that could be wrong. Some issues have similar signs while others are distinct. Let’s hit the most common stuff.

Symptom #1: Both turn signals flicker or seem dull and don’t flash, but they work fine when the 4-way hazards are turned on (maybe).

Common Cause; LED lights use very little amperage to give you lots of light. However, the regular metal “can” flasher (#552 for instance) lives by amperage. With the 4-ways on, there is enough amperage going through the flasher to make it work but either turn signal alone is too little amperage. Cure this by (a) getting an electronic flasher that is intended for LED lights [this is often a more expensive answer] or (b) add a dummy load to each side - left and right - to increase the amperage flow and make the flasher work.

Symptom #2: One side works and the other side doesn’t (or is not as bright).

Common Cause: If one side of identical circuits doesn’t work, there’s something wrong with that side. Check the ground(s), “bench test” each light to make sure they are fine, and most helpful - take voltage readings at each light and elsewhere in the system as needed. We have been finding that with some wiring panels there is unwanted resistance in the panel connections that can create a voltage drop, frequently to just one of the tail lights. And since LED’s can be sensitive to low voltage, this is a likely problem. There should be a full 12 volts all the way to the back of the vehicle and both sides should be the same.

Symptom #3: The LED lights seem fine when viewed up close but as you get farther away they are quite dim.

Common Cause: LED’s are very directional and need to point straight backwards from the vehicle. If you have put an LED bulb replacement into an existing light housing, and if that housing is on an angle, you’re not going to be pleased with the LED at a distance. For build-in and flush mount lights, the directions should explain this. There is a little bit of diffusion off center, but the best and brightest light is “straight on” to an LED.

Symptom #4: I have three different feed wires for each light on my car but the LED light only has two wires plus the ground. What’s up?

Common Cause: You’ve kind of gotten the cart before the horse in-that you have bought a light that doesn’t match your vehicle’s system. Your three different wires are for (1) the taillight, (2) the brake light, and (3) the turn signal as a separate light from the brake light (probably amber in your original vehicle). The LED taillight has been designed (as most of them are) for a vehicle with combined brake/ turn light. But those vehicles that have combined brake/turn also have designed in what is called brake light override - that is, it prevents the brake light from “overriding” the turn signal (and blocking it out) when the turn signal on one side is active. Again, the good news in that there are additional parts that will marry the light to your system and make it work perfectly. StreetWorks also has build-in, flush mount LED taillights specifically for those vehicles with separate brake and turn signal lights.

(More next time on Brake Light Override.)

Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com

The 25+, "Steering Column Wires"

Does this all sound familiar???

I got this car from someone else, and...

#19. I don’t know which wires are which coming out of my steering column. How do I figure it out?

The specific wires coming out of your steering column will depend in part on whether we are talking about an original US column, an after market, a VW Beetle, etc. and whether the ignition switch is in the column. Typically you will have a feed wire for the turn signals, two (2) or four (4) turn signal outputs, and a horn button wire. For US columns, add an emergency flasher feed and a brake light switch feed. For the purposes here, we will not address columns with wiper or other accessory controls (for those, go to the OEM diagram for that specific year/model).

If it has GM color coding, you’re in luck. The black wire is the horn button, light blue -or- black with a light blue stripe is the left front turn signal. Royal Blue is the right front turn signal, brown is the emergency flasher feed. Purple is the incoming turn signal feed from the panel flasher. Yellow -or- black with a yellow stripe goes to the left rear turn signal, green goes to the right rear turn signal. And finally, the incoming brake light feed is white -or- black with a white stripe. Remember that most US columns used for street rods have the rear light brake light override feature built into the turn signal switch in the column. Foreign columns and many newer columns do not because the turn signals and brake lights are two separate lights.

Otherwise, to find out which-is-which requires some Sherlock Holmes investigation with a Volt-Ohm meter, continuity tester or test light. For instance, to find the horn feed which is a grounding switch, test continuity between the column itself and each wire as you push the horn button. For other functions, test continuity between two wires as you activate all of the different switches. When a specific switch makes and brakes continuity, you’ve found out what those wires are for. Label as you go and keep moving on to other wire combinations.

The 25+, "Overloaded Switches"

Let's look at circuit overloading, specifically talking about switches...

#17. You mentioned the headlight switch getting over loaded when higher wattage headlights are used. Are there other switches or circuits that often get over loaded?

Lighting circuits are common problems even if they are other than the headlight circuit. For example, people who add auxiliary lights may buy a kit with a pair of spot lights or driving lights - the kit has a switch and maybe a relay - and, if the manufacturer has done their design work right, then you are good to go. But often, one set of lights leads to yet another. If the switch and/or relay in the second set gets left in the box so that all of the lights can be turned on together, then the original switch/relay will probably be over loaded by having to carry twice the lights - and twice the amperage - that it was designed for. As always, preventing an overload requires making sure that the switch, or the relay, and all of the rest of the circuit components (wire, connections, etc.) are sized large enough to handle the entire circuit amperage load.

The other most common switch to get over loaded is the ignition switch.

#18. How can you over load an ignition switch? It just runs the car ignition.

But it also supplies power to the starter solenoid and to all of the “ignition controlled” accessories. The starter solenoid is seldom a problem (it is called a solenoid because of its design, but it works like a relay in the starter circuit). But, when we add accessories powered through the ignition switch problems can develop. Very few ignition switches are rated to carry more than 30 amps of accessory power, total. Add some new power windows and an air conditioner to your car and that ignition switch will be toast.

You can protect your ignition switch quite easily by (am I starting to sound like a broken record, yet?) adding a relay with a higher amperage rating, like our 80 amp relay. It will more than double the total accessory carrying capacity, protect the ignition switch and provide more than most cars need for their system.

Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com