DFI coil high resistance - how come?

On a GM3800 engine, the coils are 6000 ohms new. On a misfiring engine, I found one was 8100 ohms. Now I have had one go open circuit. I could understand insulation breakdown causing short between windings and lower resistance. But how do you get high resistance? Bad solder joint?

Pedro Valdez > wrote:
>On a GM3800 engine, the coils are 6000 ohms new. On a misfiring engine, I f=
>ound one was 8100 ohms. Now I have had one go open circuit. I could underst=
>and insulation breakdown causing short between windings and lower resistanc=
>e. But how do you get high resistance? Bad solder joint?

An open combined with leakage across the gap. Maybe you had a shorted
turn and the shorted turn burned through and now you have a thin spray
of metal across the gap. Maybe the coil overheated and the insulation
burned forming conductive carbon paths between turns, before it went open.

You can unwind it and see for yourself if you want but it's a real pain
in the neck... even harder than older single-coil coils to get all that
tiny wire off intact.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."