Connecting external tach

I want to check the timing of my 82 SC, as it is pinging a bit under hard acceleration. The instructions for the tach feature of my multimeter say to connect it to the negative side of the coil, and to ground.

I looked at my coil, and can't figure out which is the negative side. One side has an arrow, ant the other has what appears to be an "A". There is also a picture on the coil showing a test meter of some kind wired to both coil connections, indicating that this is Verboten. The Haynes manual says to follow the manufacturer's instructions, the Bentley doesn't mention it at all.

How do I connect this thing?

Tom
82 911 SC Coupe

Tom,

Sorry, but just as you shouldn't connect your 'convetional' meter to a GM HEI ignition, DON'T CONNECT IT TO THE COIL of a CDI-system!!! Your meter is designed for connection to the primary of a conventional 12 Volt battery-coil ignition system, not to the primary of a CDI-system operating with 460 Volt pulses to the primary!

All Bosch coils for CDI-systems have a foil sticker with a large yellow Lightning Bolt on it ... warning about the dangerous Voltage present. Any clue why that sticker should be heeded and respected?

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Warren Hall
1973 911S Targa

Thanks Warren, that is why I asked, to prevent me doing anything stoopid.

Interesting that a handheld tach is recommended specificly in the Haynes book. Is there a special tach for CDI ignitions?


[This message has been edited by emcon5 (edited 03-20-2001).]

Tom,

Most of the 'modern' dwell/tach/multimeters of the past 20 years are inductive pickup that clip-on the No. 1 sparkplug lead. One of the very best, but a little pricey, is the Fluke 88. Of course it does a lot of other things, too, like injector pulse timing, temperature, and typical digital multimeter functions.

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Warren Hall
1973 911S Targa