Temp Guage reads hot & blinks at key start (cold)

1985 - Golf Diesel - TD

I realize a blinking light means coolant is low, solid is overheating. But should the guage read hot (off the chart hot) if the coolant is blinking low? This happens as soon as I turn the key (engine cold and not running, just the key to power).When it first started blinking/reading hot, it would occasionally go to normal temp when driven for a while, a few days after that, it consistently stays blinking and hot off the chart.

In other words, would fixing the coolant level sensor also fix the high temp reading that my guage is stuck at, or is it another culprit?

Pleasant note: no posts needed about head gasket, I guarantee everything is on the up with the entire cooling system(all new with recent engine replacement, all tested/working properly), this is happening while cold with only key power, reading past the guage marks, and sometimes violently tripping: problem is electrical, not mechanical.

any info on how to properly test coolant sensor would be appreciated (I have an ohmmeter, but little electrical knowledge of how to use it). Thanks

I would try the temp sensor and also maybe giving the low level sensor prongs a scrape with a screw driver or similar, they're in the coolant tank.

That is correct behavior, the gauge will peg at maximum if the coolant level is blinking low.

The level sensor is part 251919372, $2.82 at AutohausAZ.

While you're at it, if your expansion tank is nasty, get a new one, 171121407F for $12.93, and a cap, 171121321J, for $2.19.