Temp gauge fault

[jchesshyre]

I have an annoying little electrical issue. My coolant gauge stopped working (needle just moves up the tiniest amount when ignition is switched on), and following the test procedure in the manual I have:
1. Pulled the connector off the thermo sensor and grounded it. Gauge should shoot to max if wiring is OK – it doesn't, just moves a fractional amount.
2. Checked for continuity between this connector and the other end on the back of the gauge – all good.
3. Checked for battery voltage between the brown/black and green/black wires feeding the sensor. I get about 10V here while my battery measures 12.3V. I presume then that I have a fault somewhere along this wiring since I'm only seeing 10V?

A weird thing though is as I was moving the instrument cluster around just before I stopped testing, the gauge suddenly shot up to max and stayed there! The sensor connector was not grounded or connected at this point. I quickly turned the ignition off to avoid damaging it, but...WTF?

[jchesshyre]

New coolant gauge from David Silver (£25 plus VAT!) has sorted this issue

[jchesshyre]

I spoke too soon...occasionally the gauge is moving to minimum for a while then sorts itself out after a while.

I had tested the signal cable from the sensor for continuity and it's fine, so presumably this is due to a short or intermittent break somewhere in the power supply or ground cable?

[8541Hawk]

I would start by checking the ground. Man I hate electrical issues.....