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Old 08-12-2012, 11:17 PM
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Dangerous Doug Dangerous Doug is offline
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Join Date: Apr 2004
Location: Scotts Valley, CA
Cobra Make, Engine: ERA 289 FIA #2108
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Quote:
Originally Posted by Gaz64 View Post
Key on, engine off, you will have 12v both sides of the coil if the distributor "switch" is off.
I was going to call you on this one, but I thought it wise to go check, first.

You are correct.

I had a Volvo with a bad coil. Nobody could figure it out. I measured the voltage on + and - when it was running fine and then drove it around until it died on me. I checked the voltage at the + and - and found it different from earlier. Replaced the coil and the problem never returned.

I am convinced the coil was bad on my Cobra, as it acted the same way (drive around until the coil gets hot from the engine, it either shorts or opens causing the engine to die, the engine manages to cool after some time, the short disconnects or the open closes with the cooling, and off you go).

I wonder if it had a chance to cool from when I opened the hood until I could get the DMM out of the tool box in the trunk and make a measurement.

Okay, so my test was bogus, but the assessment correct.

So, for future reference: How do you properly test a coil in the event of a failure?

DD
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Last edited by Dangerous Doug; 08-12-2012 at 11:21 PM.. Reason: clarity
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