In Jainism, Chauvihar means refraining from eating or drinking anything after sunset or, in stricter practice, after a certain time in the evening (often after sunset or after dinner, usually around 48 minutes after sunset). Navkarshi is the practice of not eating or drinking anything from sunrise until 48 minutes after sunrise, at which time one may begin eating for the day.

Pacchkhan is a vow or a formal resolve taken, often in the presence of a Guru, an elder, or even by oneself, to observe certain restrictions such as Chauvihar, Navkarshi, etc.

To answer your question:

• Chauvihar and Navkarshi are distinct practices.
• Chauvihar is observed at night, refraining from food and drink after sunset.
• Navkarshi is about delaying the first meal of the day until 48 minutes after sunrise.

Do we need to do Chauvihar for Navkarshi Pacchkhan?

• If you are taking Pacchkhan (vow) for Navkarshi, you are committing to not eat or drink anything from sunset until 48 minutes after sunrise.
• Chauvihar naturally becomes part of this, as you will not be eating or drinking after sunset (Chauvihar), and continue fasting until Navkarshi time.
• If you are only taking Navkarshi Pacchkhan, you are specifically vowing not to eat or drink anything before Navkarshi time. However, for stricter practice and spiritual benefit, combining Chauvihar with Navkarshi is highly encouraged in Jain tradition.

In summary: Yes, if you are taking Pacchkhan for Navkarshi, you are expected to observe Chauvihar as part of it, since the fast extends from sunset (Chauvihar) to Navkarshi (48 minutes after sunrise). Many Jains formally take a combined Pacchkhan for Chauvihar and Navkarshi together.

If you wish to follow traditional Jain conduct, it is good to take Chauvihar before sunset and then Navkarshi in the morning.