Civic 1992 LSi strange coolant gauge raise ?

[Topper]

Hello everyone,
On my Civic made some "tunings" like LED ribbon instead of bulbs behind the gadgets. After that, or by coincidence, the coolant gauge stared raise to "H" instantly after ignition key turns on contact
Checked coolant temperature sending unit by this way

The unit works normally, from 152 Ohms to 80 Ohms after few minutes of working engine. Gauge raise when Y/W wire connect to ground. After disconnect from ground or sending unit - goes to zero.
Is it possible during dismount/mount of hud to be broken somehow. I mean there is some resistor and diode like cener, did they do some voltage diver for the gauge?
Please advice folks.
Thanks to all responders in advance!

 

[obracer12]

well the placement of LED ribbon will cause a different load on the cluster board... which may be affecting the gauge... but I would replace the sending unit first and see if it fixes it, if not change the gauge... if that's not it. the LED ribbon has to go. Form> function, I'd hate to be overheating and not know it until i blow a gasket or a pump..