Savings and loans in California continued losing their share of the home lending market to banks and mortgage banking firms in 1989, a California Assn. of Realtors survey shows.

The survey of about 1,000 association members released Wednesday showed that S&Ls funded 41% of first mortgages on homes and condominiums the realtors sold, down from 47% a year ago and 59% in 1987. The association said mortgage banking firms increased their share to 44% from 41%, giving them the largest percentage of any industry group. Banks nearly doubled their share from 1987, to 11% from 6%.

But industry executives cautioned not to make too much of the association's survey because it measured a narrow segment of the business. As a result, they said, it probably understates the role of banks in home lending and may overstate the role of mortgage banking firms, which sometimes take loans to banks to be funded.

Still, the survey is in line with other studies nationally, providing further evidence that thrifts have lost their historical place as the nation's principal lenders of home loans. The reasons include increased competition from banks and mortgage bankers, combined with a severe industry shakeout that has forced even some of the healthiest thrifts to shrink to meet tough new capital standards that require a bigger cushion against losses. Hundreds of other thrifts nationwide have been taken over by regulators, sold or closed.

The survey included only realtor members of the association, and the response rate was 10% to the 10,000 surveys sent out asking them to describe financing details of their recent sales. Because the respondents were realtors, nearly all the sales involved existing homes.

That would understate bank activity in home lending because builders of new homes frequently use their own sales staff instead of realtors and often work directly with banks to help buyers finance purchases. The survey also does not include the refinancing of homes or home equity loans, two areas where California banks have been particularly aggressive lately.

Jonathan E. Gray, a savings and loan analyst for Sanford C. Bernstein & Co. in New York, said another factor that may distort the market share figures is that adjustable-rate mortgages, a specialty of savings and loans, were less attractive in 1989 than they were in 1988. ARMs are less appealing when interest rates are falling, as was the case during much of last year.