How to bench test my electrical wiring - Request

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Hilderbrand1983

Hilderbrand1983

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As the weather grows cold in southern Indiana, my willingness to do garage jobs on my '67 Dart 270 (slant 6, 225cid) has migrated south with the birds. I have a lot of "inside" jobs, among which is testing the electrical wiring and replacing wires as needed.

However, I have no idea how to provide the necessary power to do the bench test. Does anyone know of any YouTube videos or online lists of equipment needed to test the electrical wiring? Or can anyone give me any guidance?

I'm more than happy to read a book, if that's what it takes! Thanks in advance for any pointers!
 
Define testing, usually a ohm meter from point a to b is fine if the wires are not cracked or hard.
 
I just bought an awesome test kit at harbor freight for six bucks. Comes with a test light for 6-12 volt another test light for 36 volt that you throw away, and a battery powered continuity tester.

If you need 12 volts to make lights flash and horns honk, bring your battery in the house too.
 
zkx14 said:
What are you testing? Harness, components...?
Click to expand...

Before I begin, you should know that the car is disassembled. The wiring has all been removed, but I haven't unplugged any of its connections. For example, the wiring under the hood is all still in one, long "rope" that all comes together in the harness.

I want to test the electrical continuity of the wires. That is, if I know that a complete circuit is operating, I want to use a test light to make sure that everything has power. My main interest is to see whether my fuel and temp gauges work on the instrument panel. I figure that, while it's out of the car, it is a good idea to check ALL the wires. Since it's a '67, that means that there aren't a whole lot of them, so it wouldn't take too much time.

Does that make sense?

Define testing, usually a ohm meter from point a to b is fine if the wires are not cracked or hard.
Click to expand...

If possible, I'd like to use my multimeter to test just how much power is getting through all the wires.
 
Continuity tests will find some problems. Individual components can be tested, some through wiring. A lot of issues these cars have end up being connections and the biggie for me - grounding. Those are mostly going to show up when you get everything together on the car.
 
I am by no means an authority on this subject but, our cars have some weaknesses in the electrical system... especially at the firewall connector, examine this point for corrosion and heat damage, the amp gauge is often by passed and there are articles showing how to do this...the instrument cluster is another location that needs examination to determine if any connections are broken or corroded...I suggest also adding an auxillary fuse panel with some power adding circuits for accessories... after assessing your electrical harness , if you plan on adding several devices , a new aftermarket harness may be your best bet...
 
After I suggested a battery charger to power up on the bench. Del ( 67dart ...) FABOs electrical guru who was on this site several months back said not to do that. Something about inconsistent electrical current. Do a search and see what he had to say. That being said, I used a battery charger and it worked out well.
Yote
 
Yote said:
After I suggested a battery charger to power up on the bench. Del ( 67dart ...) FABOs electrical guru who was on this site several months back said not to do that. Something about inconsistent electrical current. Do a search and see what he had to say. That being said, I used a battery charger and it worked out well.
Yote
Click to expand...
Too many ******* scientists in this world.
 
A battery charger may or may not work as a power supply. Whether it works or not depends on if its rectifier is a half wave or full wave. Also battery chargers don't have voltage regulators or filter capacitors to remove the AC ripple voltage and they will have some AC voltage in their output. DC motors do not like any AC voltage. If you connect a charger to a battery and use it for a power supply, the battery will filter out the AC, but why not just use the battery by itself.
If you want to test the instruments, you will need a setup something like what I use. I have a 5 volt power supply and a precision potentiometer to simulate the resistance of the sending units. You can vary the resistance of the potentiometer and check the meter movement and make sure it reads correctly at the proper values.
meter test 004B (800x600).jpg
 
skykeith said:
If you want to test the instruments, you will need a setup something like what I use. I have a 5 volt power supply and a precision potentiometer to simulate the resistance of the sending units.
Click to expand...

Thanks for the input. One quick question - where could I buy a potentiometer?
 
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Hilderbrand1983 said:
Thanks for the input. One quick question - where could I buy a potentiometer?
Click to expand...
You can get them from Mouser or DigiKey a precision wire wound one is what you need. I also have a resistor substitution box that lets you dial in the resistance you want. You can also use fixed value resistors if you are only going to test specific gauges.
tester 011 (677x800).jpg
 
I have a home made test unit I can lend you does all the gauges in or out of the car. Runs on a internal battery or external car battery Do not put 12vdc to the gauges.
 
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Hilderbrand1983 said:
Before I begin, you should know that the car is disassembled. The wiring has all been removed, but I haven't unplugged any of its connections. For example, the wiring under the hood is all still in one, long "rope" that all comes together in the harness.

I want to test the electrical continuity of the wires. That is, if I know that a complete circuit is operating, I want to use a test light to make sure that everything has power. My main interest is to see whether my fuel and temp gauges work on the instrument panel. I figure that, while it's out of the car, it is a good idea to check ALL the wires. Since it's a '67, that means that there aren't a whole lot of them, so it wouldn't take too much time.

Does that make sense?



If possible, I'd like to use my multimeter to test just how much power is getting through all the wires.
Click to expand...

Power through wires is the amperage of what load it will carry. A light bulb in a pigtail will show you the continuity and a small amount of load. You would need a few different size ballast resistors one for each gauge wire to load test them. Just make sure all the wires have good continuity and the terminals are in good shape and you should be fine. Having a good terminal removal tool helps out tremendously. (you have Packard 56 connectors)
 
All of our oil and temp gauges, and majority of fuel gauges will read 20 ohms across the winding ( ohm meter post to post ). Some fuel gauges ( varies with model ) will read 13.5 ohms. This test proves the winding inside is good. It doesn't prove the bi metal beam is good and the instrument is accurate, just alive. If you go to the extent of powering and testing instrument response per those suggestions above, what will you do if/when you find it inaccurate?
Attempt to recalibrate? If its out of calibration there is a fault ( bi metal beam is cooked ) that cannot be corrected with re-adjustment. A few owners/members here have poked their screw driver into those little setup provisions on the backside and totally lost the setup.
Buy another used one? You're gambling here. Odds are a used of same age will be in similar or possibly worse condition.
Plan A for the novice... Just check continuity with a ohm meter. If its alive put it back and hope for the best.
Plan B, send them to a instrument service vendor. Is plan B the best plan? They are 40+ years old.
 
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