@MukeshPatel, to test for proper power, you need a multimeter. Set the meter to measure AC voltage. Place one lead on R and the second lead on the C wire. You should see 24VAC +\- 5VAC. If you see less than 20VAC your system needs service to replace the step down transformer.
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NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.