Hi. My car is a 1989 240DL. I've decided to upgrade the electronics a bit. I'm adding a new radio/speakers, tach, volt and oil pressure gauges. The gauges came from the gauge cluster of a turbo car and have all the wiring intact up to the connector.

Several posters have helped me understand how the gauges and tach should be wired/installed (thanks to you all!!), but when I was beginning to install the gauges a question came to mind.

Since the gauges are already wired in a single harness for light and power, would it be possible to use the three prong connection on the back of the tach to power/light/ground the new gauges? A poster here explained the three terminals on the top back of the tach were to light/ground/power a small clock. Since I'm not installing a small clock, those connections would be free. My thinking would be to remove the turbo gauge, leaving the wiring for the voltmeter and oil pressure intact. Putting spade terminals on the ground, power and light wires from the gauges and connecting those wires to the three terminals on the back of the tach. I would still have to run an independent wire to the oil pressure sending unit.

My concerns are:

1) Would it even work?
2) If it did work would pulling power for both gauges overload the tach circuitry?
3) If the power demands would be too much, could I just run the lights (off/on/dim) through the tach connections, powering the gauges from a key-on source?

Using the tach connections would make the installation much easier and cleaner (especially for the lights!) instead of splicing into the existing wiring harness to light/power the gauges.

Thanks!!