Have another project on my '87 740GLE. I picked up an instrument cluster on Ebay with the two optional gauges I'd been looking a long time for. However, in addition to the voltmeter, what I thought in their unclear picture was an oil pressure gauge turned out to be an oil temp gauge. Undaunted, I inserted both in my existing cluster so I didn't have to swap the speedo module.

I checked with the Volvo dealer and the sending unit for the temp gauge was so rare that they no longer have a part number for it. It was a simple oil drain plug with a sender threaded in it. I will have a machine shop make me one from a new drain plug and a temp sender. But I can't find any schematic to show me the wiring for it. On the salvage cluster the oil temp gauge has three wires on its back, red, black and yellow. They go 4 inches to a connector that the yard clipped the outbound wires from the dash harness. No clue their termination. In the connector, the red gauge wire goes to a red/blue wire, black to black and yellow to red/green. The only schematic I have is my Haynes 740 manual and the schematic shows blank for that part of the cluster schematic. Does anyone know what wires connect to power/ground and the sender? Can I assume the red to 12v power, the black to electrical system ground and the yellow to the wire to the connector on the sender? If that's the case, I'll simply thread a yellow wire down to the sender from the dash. Hoping for simple!

I intend to activate the oil temp gauge but I will still keep looking for the illusive oil pressure gauge.

Thanks once again for your help!

Roger
Southern CO
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'85 240 DL B230F 4spdOD 330K; '87 740GLE B230F ZF22 340K