Temp Light Still flashing

After reading some of the posts on here I’m still in need of some help on a  1990 1.6d Caddy, the temp dash light keeps flashing constantly!!

BUT goes off if I turn the lights on and only if I put the main beam on

here is what I’ve done so far to try and fix it.

1) Replaced both sensors in the coolant housing which fixed the temp level that wasn’t working.

2) Replaced the coolant expansion tank prongs switch and also checked voltage is going to them, I have also bridged the prongs to see if it would turn the light off but it didn’t turn off.

3) Pulled the replay no42 which didn’t stop the light flashing but then didn’t allow to the car to fire up ( unsure if this is the correct relay ? )

4) Check voltage to the block temp switch and changed the spade as that looked a bit worst for wear.  I’ve not changed the switch sensor in the block as the gauge dash gauge started working from changing the sensor in the coolant flange housing so was unsure if this does anything?

Anything else I can do?

Cheers

Sounds like bad Earths.  If your Battery-to-Frame-Engine/Transmission grounds haven't been replaced ro cleaned then now is the time to check it.

You can do a voltage drop on the Battery to Earth to see if your cables are bad, but on a 30 year old cable I would suspect that you need to replace them.

You can also do my add a earth to the back of your clocks so that you have good ground connections on them.
See:
Improving your Cluster Connections and ground. | Volkswagen Owners Club Forum