Consumers continued to display confidence in the economy in November, adding $4.1 billion to their outstanding debt burden, the Federal Reserve Board reported yesterday.

But the large increase in net borrowing, the biggest since Hune, is something of a mixed blessing for the economy.

While consumers still seem willing to borrow to spend, and therefore keep the economy expanding, some ceonomests are worried that consumers are overextending themselves and will abruptly stop borrowing and slow their purchases.

Should that happen, the ceonomy could go into a tailspin, many economists say.

But so far there is little evidence that consumers are having any troubles repaying their debts, although the Federal Reserve Board repayments were smaller in November than the month berfore.

Consumers repaid $22.12 billion in November, comparedd with repayments of $22.38 billion in October.

Consumers borrowed a total of $26.21 billion in Novemver compared with $25.76 billion in October. The total amount of consumer credit outstanding at the end of November was $269.5 billion, nearly 20 percent higher than a year ago.

Consumer credit includes bank loans and credit cards, but koes not mclude home mortgage loans.

Economists hope that consumers will slowly wind down their borrowing rather than cut it off abruptly. Outstanding consumer credit grew at an annual rate of 17 percent in the third quarter and during October and November. In the second quarter it expanded at annual rate of 21 percent.

Presumably consumers used some of the heavy November borrowings to finance Christmas purchases. Preliminary evidence indicates that merchants, who were worried early in the Christmas buying season, enjoyed a substantial increase in sales last month.

The Fed reported yesterday that new loans for automobiles total $7.8 billion in November, up from $7.5 billion in October. After repayments, the net increase in automobile credit was $1.76 billion, compared with $1.38 billion the month before.

Revolving credit -- such as department store or bank credit cards -- increased $665 million in November, after rising $346 million the month before. Miscellaneous consumer debt rose $1.6 billion in November, compared with $1.63 billion in October.

The Feb said that it had underestimated the net increase in consumer credit in October, revising it up to $3.37 billion from the preliminary estimant of $3.12 billion. Consumer borrowing rose $3.68 billion in September.