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Whats the best way to test a ignition coil?

 
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red924  



Joined: 13 Oct 2003
Posts: 281
Location: London, England

PostPosted: Fri Jul 30, 2004 10:03 am    Post subject: Whats the best way to test a ignition coil? Reply with quote

As above really, I checked to see whether there was a spark or not, I want to find out for definate before I buy a new one! Its the later bosch coil by the way.

Thanks
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1982Porsche924  



Joined: 14 Nov 2002
Posts: 679
Location: Cupertino, CA

PostPosted: Fri Jul 30, 2004 10:48 am    Post subject: Reply with quote

Check continuity between the + and - terminals. Should be about 100 ohms. Check between + and top of coil. Should be closer to 10,000.

or was it - and top of coil = 10,000?
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Engine: Euro pistons, Light Flywheel, Weber TB, Bursch Header, Cam Wheel
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Sleykin  



Joined: 30 Apr 2003
Posts: 758
Location: Medford, Oregon USA

PostPosted: Fri Jul 30, 2004 10:54 am    Post subject: Reply with quote

There is really no way to be definate about it. You can check primary and secondary resistance against the specs, but since it is an autotransformer with a single winding there is no practicle way to determine the state of the internal insulation. Thermal faults my not show up under most test situations. The high voltage output is a function of the inductance and capacitance in the circuit and the time of the pulses applied. Even using a test set for testing coils is not 100%.
On the practical if the DC resistance is within spec it should be ok.
...
Sorry about the EBS I must be in a bad mood
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red924  



Joined: 13 Oct 2003
Posts: 281
Location: London, England

PostPosted: Fri Jul 30, 2004 11:23 pm    Post subject: Reply with quote

cheers guys a new one is an expensive way to find out
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garthfan  



Joined: 28 Feb 2004
Posts: 226
Location: Manchester, NH

PostPosted: Sat Jul 31, 2004 5:24 am    Post subject: Reply with quote

Lick your finger and touch the output while a friend turns the key....
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garthfan  



Joined: 28 Feb 2004
Posts: 226
Location: Manchester, NH

PostPosted: Sat Jul 31, 2004 5:25 am    Post subject: Reply with quote

...okay, before I get flamed by certain know-it-alls about giving dangerous information to inexperienced people...it was a joke.
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gohim  



Joined: 02 Nov 2002
Posts: 4459
Location: Rialto, CA

PostPosted: Sat Jul 31, 2004 10:02 am    Post subject: Reply with quote

Coils seldom go bad.

Are you sure that you are having a spark problem?

Have you tried holding a spark plug lead with an extra spark plug close to achassis ground wile cranking the engine to see what the spark looks like?

If you get no spark, and you have voltage at the coil, you need to check the magnetic pickup module inside of the distributor to see if it is working, before you assume that the coil is the problem.
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