Ignition Colis and Ballast Resistors

 IGNITION COILS

 Single Ignition Coils



there are two different parts to test on an ignition coil:

Primary windings, to test these you have to set you multimeter to resistance on the 20ohms scale, put your prongs on the two primary terminals of the coil. this makes sure that the primary windings in the coil are not touching the secondary windings. the reading you should get is somewhere between 0.1 and 0.9ohms

as demonstrated in the image below:

image is from: www.farmallcub.com

To test the secondary windings, keep your multimeter set to check resistance and place one prong from the multimeter on a primary terminal of the coil and the other prong in the secondary part of the coil (middle). the reading you should be getting can range from 5 ohms to 10 ohms this also makes sure that the windings in the coil (primary and secondary) are not touching and there is not too much resistance in the windings:

as demonstrated below:

image is from www.farmallcub.com

Wasted Spark Ignition Coils

www.nzefi.com

The idea of a wasted spark ignition coil is to spark two spank plugs at once (one on the power stroke and another on its exhaust stroke). this was because if there is any unburnt fuels they will be re burnt on the exhaust stroke and creates better fuel economy.

there are two different types of tests you do on this coil, one is a test between the two secondary windings that will spark at the same time. (you would test this 3 times for the 3 different coils on the picture above)

you test these by setting you multimeter to resistance on 10 killer ohms, you then place your prongs of your multimeter on the two secondary parts of the coil that you are testing.

the reading you get should be around 8.5kohms, this is a good reading and shows that there will be good spark to the spark plugs.

www.evgen-autotronics.blogspot.com

 the other check you need to make is in the primary windings. these are the windings that make a magnetic field and charge up the secondary windings. to check these windings you put your multimeter on resistance. and place your prongs on pin outs on the coil, depending on manufacture specifications. the reading should generally vary depending on manufacture.

BALLAST RESISTORS

www.farmallcub.com

in the above picture is a ballast resistor, this goes in the circuit before the positive primary winding and lowers the voltage and amperage going to the coil so it doesnt over heat.

to test this ballast resistor you set your multimeter to resistance (20 ohms), you then place your prongs of the multimeter onto the prongs of the ballast resistor. you should then get a reading of around 1.5 ohms depending on the manufacture specifications. if your reading is below or close to the specifications it is able to be reused.

www.mohebghazi-electronicsystem.blogspot.com

Measuring current draw and voltage drop:

to measure the current draw you need to hook up a coil and ballast resistor in series with your multimeter and a 12 volt battery supply:

the current draw i got was 4 amps, anything around there means there is good current draw, this is the current that the coil is drawing to charge.
i then had to measure the resistance across the coil and ballast resistor as explained is the previous tasks.
coil resistance = 1.3ohms
ballast resistor resistance = 1.7ohms



once i had these resistances i was able to calculate the voltage drop across the coil and ballast resistor:

coil:
4amps x 1.3 resistance = 5.8 voltage drop


ballast resistor;
4amps x 1.7 resistance = 6.2 voltage drop

i then measured the the voltage drops myself with a multimeter:
coil:
4.7 voltage drop

ballast resistor:
6.83 voltage drop

the voltage drop across the coil was quite far out of specification because i left my voltage supply on for a while and it got quite hot and added more resistance in my coil.