Only marking on the rail was 30 3 IV CMC 7

Handy Person from CA

Nov 1, 2025 12:14 pm

Hello,
Please find attached 5 photos showing the broken window spring. The windows in the home are original to 2003 and slide up and down and latch in the middle of the lower window. I was unable to find any manufacturer tags.
Any help in identifying and replacing this part would be greatly appreciated.

5 user uploaded images

4 Replies

Bob from SWISCO

Nov 3, 2025 3:32 am

Hello there. This looks like either an S380-31 or S385-31 Channel Balance. The only difference between these two balances is the depth of the bottom nylon shoe. See below. Measure your old balance's shoe to see what matches best. For a stamp option choose 3030.

Comparison of the S378, S380 and S385 balance shoes.

Handy Person from CA

Nov 7, 2025 7:36 pm

Hi Thank you for your response.

I measured and the bottome dept is 1-3/32. I don't think the window is more that 18-20 pounds, but would the 3040 be overkill?

thank you so very much for your help. I'm recovering from hernia surgery and not supposed to lift for 6 months. this window usually get opened everyday in the hotter weather by my wife and rarely in the winter. Once I replace the two on this window, the window is a set of three and I plan on ordered 4 more to replace those while I'm at it.

I'm truly impressed by Swisco's customer service. Qualites rarely found or observed by companies in todays market.

Respectfully,

Mark

Bob from SWISCO

Nov 8, 2025 10:18 pm

Thanks for the kind words, Mark! I appreciate it. We are happy to help.

If the shoe depth is 1-3/32", then it's a dead ringer for a Series 385. As far as the stamp option, its always best to go with the stamp option that denotes the weight range your sash falls in. If the sash is somewhere around 19 pounds, that is within the 16 through 23 pound range that the 3030 stamp covers. A 3040 stamp would prove too strong for the window--the sash would continually drift upward and be very difficult to close. There's sort of a 'Goldilocks'' principle with balance stamp options--it can't be too weak, nor too strong.

Please let us know if you need anything else!