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Bosch Ing.
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009 & Switches

RPM Limiter

Spark Plugs

*Elec Ing

*Electronic Ing.

    10/24/08*

To check the ignition coil primary side resistance, have your ohmmeter set on the low scale and connect the ohmmeter leads across the primary terminals of the coil and read the ohms.

 A coil that requires a ballast resistor should read about 1.0 ohm. The stock Bosch VW coil or the Bosch HD Blue coil with the internal resistor will read 2.0 to 4.0 ohms.

If the wrong coil is used with the electronic Ignition, *ck the Ignition may be ruined.

To help mess things up Bosch has yet another Blue Coil like the one in photo. This is the new Bosch Blue sold as the Mexican # 00012. 
It has a sticker on the coil that states "No Resistor" But it does have the internal resistor as you can see by the reading on the ohm meter. It seems they are just using the wrong decal on the coil at present.


Ignition coils seldom go bad. However if all the other ignition components are OK and the car still misses or is hard to start, check the coil.  A simple check can be made by disconnecting the high tension wire from the center terminal of the distributor cap and holding it about 3/8" to 1/2" from a good ground like the engine case. Open and close the points by hand or have someone run the starter while you observe the spark jumping to ground.  If the spark is weak and yellowish, fires only when the cable is moved closer to the case, or fails to fire at all, the coil is probably week and should be replaced.

Use a voltmeter to make sure you have 12v between terminal #15 (or + terminal on coil) and ground.
With the voltmeter check the voltage between terminals #15 and terminal #1 This must be less then 9.6v