How to Check High-tension Circuit in a Car

How to Check High-tension Circuit in a Car

A high-tension cable carrying high voltage current from the secondary winding coil to the distributor and finally to the spark plugs make the high-tension or secondary circuit in a car. Failure in any component of the high-tension circuit can cause the ignition system to misfire. You can easily test the high-tension circuit using screwdrivers and pliers with thickly insulated handles. However, you have to be extra careful while dealing with the high-voltage current. Read on to find out how to check the high-tension circuit and replace any faulty components.

Safety Warning

High-tension circuits carry very high-voltage electricity that can cause electrocution accidents. Make sure your hands don’t come in contact with any components of the high-tension circuit while the ignition is on. Also, be careful not to touch any metal part of the tools you are working with.

Components of the High-tension Circuit

If you are experiencing ignition failure, you need to check the following components of a high-tension circuit for any faults or damages.

  • The high-tension leads
  • The secondary winding in coil
  • The condenser
  • The rotor arm

How to Check High-tension Circuit

One by one, check each component of the high-tension circuit to single out the faulty component. Once spotted, it is best to replace the faulty component as soon as possible to get your car’s ignition system working again. But before that, you should first update your charging system so that your car has a good power transmission.

High-tension leads

Start by visually inspecting the leads for any damage or signs of wear and tear. A damaged lead might have signs of abrasions, corrosion or burn marks on it.

Step 1 – Using a multimeter, you can conduct a resistance test on the leads.

Step 2 – Set the multimeter on the Ohms option; the symbol for Ohms is similar to a horseshoe.

Step 3 – Disconnect the lead that needs to be tested.

Step 4 – Using a measuring tape, measure the lead and manually calculate the resistance if it is not already marked on the lead. For every one foot, the lead should have 12000 Ohms of resistance.

Step 5 – Now measure the lead’s resistance by placing the multimeter’s probes on both its ends. You can remove the plug caps to access the inner core of the lead by the probes.

Step 6 – If the reading is more than the resistance that you have calculated, replace the lead.

Alternate Test

If you wish to find the exact spot from where the high-tension lead is damaged, you will need to use a 12-volt test bulb. Ground one end of the bulb with the engine. While the engine is running, using insulated pliers, move the bulb along a lead. A spark from the lead will jump to the bulb if the lead is damaged.

Secondary winding of the Coil

Step 1 – To check the secondary winding inside the coil, you have to detach the distributor cap and the high-tension central lead from the distributor.

Step 2 – Now, remove one of the spark plugs.

Step 3 – Switch the ignition on.

Step 4 – Using the insulated pliers, grab the high-tension central lead and put it over the spark plug terminal from where you removed the spark plug earlier.

Step 5 – Open the contact breaker points using an insulated small screwdriver.

Step 6 – If a strong spark is visible, then the coil is working fine; if there is no spark, there is a problem.

Condenser

To check if the condenser is working properly or not, you have to run a spark test, and you’ll require some assistance as well.

Step 1 – Start off by removing all the high tension leads from the distributor so that the engine does not start.

Step 2 – Carefully mark all the leads so that there is no confusion when you have to put them back in place.

Step 3 – Now, remove one of the spark plugs and connect it with the high-tension lead using the insulated pliers.

Step 4 – Ask a helper to start the engine and bring the plug and the lead near the engine.

Step 5 – If a blue white spark appears, then everything in the circuit is in order. However, if a weak orange red spark appears, then there is a problem with the condenser.

Step 6 – Replace the condenser if required.

Step 7- You might also want to change the spark plugs if they appear worn out.

Rotor arm

A rotor arm can short circuit. To check if it is working fine, you can test it with the high-tension central lead.

Step 1 – Remove the high-tension lead from the distributor using insulated pliers.

Step 2 – Ask a helper to start the engine.

Step 3 – Place the exposed end of the high-tension lead about an inch away from the rotor arm tip.

Step 4 – Now, using an insulated screwdriver, flick open the points of the contact breaker.

Step 5 – If the rotor arm is functioning properly, then there should be no spark. A strong spark implies there is a short circuit in the rotor arm.

Step 6 – Replace the rotor arm if needed.

Note: Unregulated voltage can cause damage to all the electrical components in the car. In case of a faulty voltage regulator, it is best to immediately buy and fit a new voltage regulator in your car.

There you go easy ways to check the high-tension circuit in the car. You should test the car’s battery to see if your car needs a new battery. Also, test the alternator to see if the voltage output is fine. If the car still does not seem to start properly despite all the tests and changes in the high-tension circuit, there might be other reasons your car is not starting. Try looking out for signs your car needs an oil change. Change the engine oil, if necessary.

Knowing how to check high-tension circuit can be extremely beneficial for you if you have trouble with your car’s ignition. Simple tests can help you instantly find the fault and fix it immediately, without any professional help from the mechanics.

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