Weathershield Wood Double Hung Window circa 1995

A quick learner from Texas says:
November 11, 2020
Long neglected garage window needs attention. The upper sash locking cam has dropped on one side. The wood window sashes are structurally sound but the balances probably need to be replaced. Weathershield no longer offers jamb kits on windows this old -- I did find the 1999 Weathershield tilt window parts catalogue online and the 20HD balance code means white part 980982.

What parts do I need to replace the side spring assemblies for the upper sash? Will the new parts fit into the existing vinyl side channels?

I was able to remove both sashes from the frame but wasn't confident in disassembling the sides to investigate further. The lower sash works properly.
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Bob from SWISCO responded:
November 16, 2020

This looks like an S751-21 Ribbed Channel Balance to me, with a stamp option of 20HD. Just make sure that your balance's shoe matches the one that comes attached by default to these balances (our 15-014). Let me know if it differs at all. The video below shows how to remove and replace this type of balance. 
A quick learner from Texas says:
November 17, 2020
Thank you. I'll place an order for the replacement S751s. Followup question: any advice on obtaining replacement vinyl jambliners without buying a full sash replacement kit?
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Bob from SWISCO responded:
November 17, 2020

That can be tricky, as they need to be tailored exactly to your window, which is why it's hard to avoid appealing to the original manufacturer. If it's a wood window, a millwork might be able to set you up with replacements. Otherwise you might need to see if a local pro or hardware store could help you. 
21" Series 751 Channel Balance
21" Series 751 Channel Balance
S751-21
$10.56
How to install a ribbed tilt channel balance with knife lock shoe
How to install a ribbed tilt channel balance with knife lock shoe
VIDEO
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