How to determine sash-weight

Question

I have a Milgard window with bad plastic pulleys, that pinch the cords in both of the 29" channel balance springs. I have ID'd the top and bottom plastic fittings on the balances from your photos, but I need assistance to determine the proper weight selection. Should I weigh the moveable single-hung window panel and divide the weight by two, half for each of the left and right balance, or do your part-numbers consider the full sash weight be applied for both balances?

Thanks,
Scott S

Tom · Accepted Answer

Measure the weight of the sash and compare it directly to the chart on the S390-29 webpage. The chart accounts for both balances, as well as friction supplied by the window frame. No math and no adjustments are needed.