I replaced brand new thermostat but the engine.

ARE YOU SURE THE THERMOSTAT WAS THE CORRECT TEMPERATURE RATING?

AS FAR AS "not heating as usual"

THE ENGINE?

. OR INSIDE THE VEHICLE (COCKPIT ENVIRONMENT)?

FEEL THE HEATER HOSES WHERE THEY ENTER THE FIREWALL. WHEN THE RIG IS AT OPERATING TEMPERATURE

IF YOU WRAP YOUR HAND AROUND THEM---IS THE HEAT ALMOST UNBEARABLE (TOO HOT TO HOLD)?---ARE THEY WARM?---COLD?

YOUR TURN

THE MEDIC

The fan fuse was blown off. So I replaced the fan and the resister. The check engine light is off. However, when I drive the temperature does not hold it comes down to below quater mark. What else could be the problem
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It sounds like the thermostat is stuck open. If it is closing and restricting the flow of coolant like it is designed to, the engine would heat up for you.