Observe the reading you get on the multimeter. If the multimeter reads within the range according to the specification in your service manual, then your primary winding is functioning well and you can go on to check the secondary winding. If you find the reading to be even slightly out of the range then you should replace the ignition coil.
To test the secondary winding of your ignition coil: The secondary winding of your ignition coil sends the spark to your distributor and then to the spark plugs. A weak spark or no spark at all is an indication that the coil needs to be replaced.
To test your ignition coil is secondary winding, attach the probes to the outer 12V pole and the center pole of your ignition coil. The center pole is the spot where the main wire is located that connects to the distributor. Again, check the reading to make sure they fall within the specified range as indicated in your car’s service manual. If your coil falls within that range all is well. If the reading should fall even slightly out of the specified range, then you should replace your coil. Remember a failing ignition coil will cause your engine to run rough and can cause other problems as well.