window replacement spring

Thanks for posting. It's tough to say. That 'D' could translate to 4, which means you'd need the 4 pound spring. But I can't be certain. I think the best thing to do is to weigh the window sash. Give me that exact weight, and I can work out the spring weights you need. 

Also, if you're not entirely certain you need Series 180 Coil Balances and want to confirm, feel free to send me a picture of the pivot shoe the coil balances work with, and I'd be happy to corroborate. 

Thanks for these photos, they're a huge help! While I agree that your old spring resembles our Series 180, I don't think that's what you want here. In fact I suspect someone used the wrong spring during installation. The Series 180 is meant to go inside a pivot carrier and then screw into the window frame at the top of the window track, which is not how your spring is being used. 

I would suggest the Series 190, instead. This is designed to install on a shoe exactly like yours.

With a sash weight of 14.4 pounds, I suggest using one 7 pound spring on each side. That will give you 14 pounds of total support, so that should be perfectly sufficient. See our S190-740.