temperature gauge

[Gyrene]

1990 240SX installed a crate motor from a parts store about ten years ago. I've been having a problem with my temperature gauge when I get to high rpm's it bottoms out to 0 but when I sit idling it works great. Changed the thermostat thinking it might be stuck open but didn't fix the problem what can I do?

[centralcoaster33]

Hmm, there are two sensors on the engine near the throttle body. One is single wire and that is for your gauge, the other is dual wire and that is for your engine computer. The single wire sensor I believe grounds to the engine. You might want to check your engine ground wires.

You can download your FSM and try diagnostics according to the instruction in there. Here's a link:
http://www.nicoclub.com/nissan-service-manuals

[Gyrene]

thank you centralcoaster33