1980 C10 temp light remaining on. VERY frustrating!!!

[kaysboat]

Hello,

I have a 1980 Chevy C10 with the 250 Straight six and temp light (as opposed to the gauge).

The temperature warning light is staying on even from initial start up and I don’t know what the issue is. So far I have:

1. Ensured coolent was topped up;
2. Flushed coolent;
3. Checked that coolent was circulating (rad temp fine, hoses warm, heat from heater etc...)
4. Changed thermostat;
5. Changed temp sending unit (heat sensor);
6. Ensured fuse was 20 amp and not blown; and
7. Took it to a shop. They checked the temperature of the coolent (runs about 190 degrees) and did a sniff and chemical test of coolent to ensure head gasket not cracked. It’s not.

At this point I’m stumped, and although I’m pretty confident in driving it without it actually overheating, I hate driving with warning lights on. Any help/ideas would be great.

Thanks.