Alcoa 1996 vintage window balance replacement

A quick learner from Belton, Mo says:
I have several Alcoa (1996 vintage)widows that need the balances replaced.
The series 600 Spiral Balance with blue tip appears to be the correct choice. Using your online measurement guide I get measurements of 31 1/2" for the balance tube not including the tip. Do I order a 31" or 32" replacement balances?
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Paul from SWISCO responded:
Good Afternoon,

Thank you for posting on the discussion board. Can you please give us the length of the internal spiral portion? This will help us in our research.
A quick learner from Belton, Mo says:
The Spiral portion of the balance is 19 inches. I will attach a photo for your review. Thanks for your help.

User submitted photo of Alcoa 1996 window balance.
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Mike from SWISCO responded:
Bob, we need the length of the internal spiral (the part inside the spring and tube with the small pins on the end.
Photo to show user the internal spiral.
A quick learner from Belton, MO says:
The internal spiral measures 32 5/8 inches.

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Donna from SWISCO responded:
Hi Bob,
The Series 600 spiral balances have an internal spiral rod that measures 1" over the tube length. So, this still does not help in which balance to try, the 32" Series 600 has a 33" internal spiral and the 31" Series 600 has a 32" internal spiral. I'm not sure if the approx 1/2" will make a difference.
A quick learner from Belton, Mo says:
I have Alcoa 1996 vintage windows and using the balance charging tool, I cannot get the balance to release from the pivot shoe. Close examination of the shoe indicates there is some kind of one way retainer clip keeping the balance from releasing.
Any suggestions??

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Paul from SWISCO responded:
You may have something similar to the Swisco 26-028 Tamp-R-Lok on your pivot shoe. To remove it, slip a flat head screwdriver under it and pop it out.
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