First the battery went, then the brakes, and now you find your car needs a new generator. Is it time to "start fresh" by investing in a brand-new car?

A new automobile is a major investment, increasingly so as prices go up many times a year. Now is a good time to make cost comparisons:

How much does it cost to own and operate the car you now have (gasoline, taxes, car payments and insurance) for a year? If it is paid for, and the insurance and tax rates are decreasing annually, you probably are making some headway financially -- until you start to need major repairs.

How much more a year would you be paying for expenses on the new car of your choice in the same period of time, including sales and excise taxes, gasoline, higher insurance costs and loan-plus-interest payments?

Based on your car's past record and its reputation on the market, what would be the estimated cost of repairs to keep the car running for, say, the next five years? Now compare the likely repairs that would be necessary on a new car with a good reputation, over the same period. What would be the estimated resale value of each at the end of that time?

How much has the price of the new model increased in the past year?

One motorist considering the purchase of a new car sat down and did some rough estimating. She figured on buying a $5,000 car under a three-year loan. (The trade-in value of her present car was $2,000, which meant she only would have to take out a loan for an additional $3,000.)

She found that several banks required 20 percent down on the total principal, and discovered that within that three-year period. She would be paying approximately $1,500 on interest, additional costs on the excise tax, sales tax and extra insurance coverage -- all extra costs above what she would be spending on her already-paid-for 1975 car, with the exception of a few dollars a year for excise tax. (Taxes vary from state to state.)

The motorist decided to keep her old car, which was in relatively good shape. She reasoned that $1,500 would pay for a lot of repair work, and she would be free of the monthly payment on the principal (another $84 a month.)

Other consumers, however, want and can afford a new car and are willing to commit themselves to its purchase, regardless of the extra cost. And for those who can afford to pay outright for a new automobile, the loss is not as great.

Now the question: If I decide to keep my old car, how much repair work is necessary to get it into reasonably good, safe shape? The basic checkpoints are engine, transmission, chassis, exhaust system, the front and rear ends and the body.

Other questions to ask yourself:

Has the car been tuned up regularly during its "lifetime?"

What is its repair record so far?

Is your car a make and model known for its particularly good (or bad) maintenance record over a period of several years?

Has the car ever been in an accident or abused through rough treatment?

Does it get good mileage ?

Has most of its mileage been accumulated on open roads or incongested city traffic?

Is your car a model currently in demand due to good gas mileage or other special features?

Was it rustproofed when new?

Are you interested in buying a new car for looks, comfort or other personal reasons, or are you interested merely in a reliable, if somewhat battered, relatively cheap means of getting around?

The "book value" of a new car would be higher than for your old car, but any repair work done on your current model will increase its resale value, especially if you sell the car privately and not through a used-car dealer. And, really, it's what that "old clunker" is worth to you that counts.