Rob Edwards

Here are the specs for the primary and secondary windings for Euro 84S through 1995 coils. You can see terminal 15 is the (+) terminal, 1 is the (-) terminal, and 4 is the coil plug connector, per DIN 72552 standard.

DR

Hi Randy,
I hope the above in bold is a typo and you meant to make that plural, as in 2 new coils. Please replace both coils.

Cheers,

Dave

Randy V

The bracket that holds the coil in place is wired to ground. Why is the exterior of the coil grounded through the bracket?

Randy V

OK, Dave - will order the other one!

SeanR

Should be grounded from the coil bracket to the block on the lift point behind the cam gear.

soontobered84

I thought my driver's side coil was bad on my GTS, but what was happening was the plastic cover was just deformed enough that it was pushing my coil wire out enough to prevent clean spark. You might just check it.

docmirror

The high voltage inside the coil causes some stray EMF to wander around the case. Usually it's no problem, but that coil is close to the hall sensor, which also uses small currents to manage the engine firing. Grounding the case with an actual wire to the ground plane of the car will help reduce those stray voltages. You may not be old enough to recall, but back in the day of AM radios, when the coil wasn't sufficiently grounded, one could hear a slight whine/buz from the coil firing, it would go up and down with the RPM of the engine. Could also be caused by a leaky condenser. Modern cars(well, relatively speaking) are more prone to issues with leaking grounds. The 928 seems particularly troubled by this, although it could be that all these cars are > 30 years old as well.

GregBBRD

The good thing about the 927 602 801 00 coil covers is that they help keep water from getting to the coil.

The bad thing is that once water gets inside, it is really difficult for it to dry out.

That rusty mess has to be from water being trapped inside that coil cover.

jcorenman

Just a thought here: The original (black) coils last just about forever, if not abused. Abuse, in this case, includes disconnected/burned/corroded secondary (high-voltage) leads. With no spark plug connected to limit the voltage, the current spike finds the path of least resistance-- which is to arc internally, damaging the secondary winding. The resistance check (above) may not catch that-- swapping for a known-good coil is the best test.

Which leads to the next problem: Lots of failures have been reported with new (silver) Bosch coils, even after eliminating the cheap counterfeit ones. They just don't make them like they used to.

We experienced this ourselves: We swapped our original black coils for shiny new (silver) ones with the cosmic GB 6L motor, and a year later we're limping home on four cylinders. Sure enough, bad coil. I swapped in an old black one, and then bought a few more old black ones from Mark at 928 Int'l for the other side plus a couple of spares. Life is good, touch wood.

We've had a couple of cars with COP's (coil-on-plug) and they are just as big a pain. The Audi (4.2L v8 allroad) had a couple fail, and the Cayenne which we have now showed intermittent misfires so I replaced them all-- and it turns out that they've been through about six different part#'s.

soontobered84

I bought the new silver coils for my GTS when I was having a problem and swapped them in and left them.

I still have the original black coils though. .

I guess I need to quit trying so hard to give them away.

skpyle

That does NOT fill me with confidence. I bought a pair of new silver Bosch coils for the Red Witch in 2016. I have not yet installed them, and have kept the original black coils. I will clean them up and keep them as back-ups.

DR

Seth,

Don't go getting all paranoid, there was a "dark period" concerning some of the "silver" coils"..but I am pretty sure you missed that rodeo.

But I found if you paint the silver ones black they last just as long as the originals.

Cheers,

Dave

davek9

Just a note on installing the coils and that plastic weather cover.
The coil wires should be dressed inward and behind the plastic posts on the top of the coil, this way the coil wire harness is directed to a narrow point exiting the top of the coil.
By doing the wiring this way it allows the wires to dress easily out (w/o stress) that narrow opening in the cap.

When installing the plastic Cap make sure you point that cutout towards the bottom allowing any water to drain and also help prevent water ingestion.
Also when doing the right side I suggest moving the coil in its holder about 10mm towards the front of the car, as this will aide in removing the Right T belt cover for checking belt tension in the future w/o having to remove the coil

Dave

DR

Wow Dave, great tips, thanks for sharing!

Cheers to you,
Dave

Randy V

Good tips on properly orienting the wires and cap, Dave - thanks!