Gee when I went to school and became and EE I was taught how to do these neat little tricks. It is called improvising. Also note that looking at a VOM while in your hand next to the cluster is the same as checking your speed, temp, fuel level, RPM's or even the clock. If you can not look at your speedo and still see traffic with your peripheral vision then you should not be operating a motor vehicle.

Sorry but any moron can check there speed and drive at the same time, so why not look at a VOM digital display. And I am not saying do this in rush hour traffic.....

As for piercing a wire, it is something that is common practive in the electrical industry, otherwise they would not make and sell regular wire probes that pierce a wire so you can check for voltage, like the standard little tester with a lightbulb in it. Now for higher voltage no you do not pierce the wire. Like when I was working on TV transmitters with over 5KV going through wiring, no you never pierce the insulation. At 12V it is ok to do without causing injury to yourself. Albeit I have been zapped by a wire with ****ty insulation on it and 7KV going through it. Those wire are tested by sliding the connector out a hair and probing at the connector. Unfortunately the way the MB connector for the O2 is you can not slide it out and probe without breaking the connection and I am not buying an MB Breakout Box to test the O2 once or twice. So you must improvise.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....