16" spiral balance replacements

Thanks for contacting us. First, can you confirm that the S900-16 was the proper replacement? Did it have the same length and diameter outer tube as your original? Also, what is the weight of the sash these balances are supporting?

Hmm... it's odd that a Red Tip didn't carry that kind of weight. You should have been good to go after 2 or 3 charges, assuming this was the correct balance. The only thing I can think of is that you need something different, but without more detailed information on the originals I cannot be sure what. I would triple check the diameter of the outer tube to be sure it's 3/8" and confirm the weight of the sash. In my experience, this kind of thing happens when a skinnier 3/8" balance is used to replace the thicker 5/8" Series 600 balance, but that's no guarantee.

That'll explain it. I would recommend our Series 600 spiral balance. I think your old White Tip might correspond to our modern Red Tip, but the only way to be 100% sure is to have the sash weight.