Replacing balance

Question

Replacing 10 window balances for 5 windows. First attempt followed all the steps from videos and closed window. On both sides the spring/balance disconnected from cylinder. That would make me think that the size was off but the sizes match up. S900 series 28 inch red tip. Not sure what to do from here.

User submitted photos of a window balance.

Tom · Accepted Answer

You mention that the tube size match up, but what about the inside spiral? Can you confirm that these are the same size?