Install Return Air Flaps

[SGKent]

I looked but did not see a specific thread.

When installing the return air flaps in the shroud to heat exchanger on a late bay, the most important step is checking them. Do not assume that if they flapped before putting the covers on, that they will flap when done. Sometimes they can rub or be trapped in a way that they will either not open fully, or stick open. Sometimes they can even be lodged closed. I use an endoscope that I fish down into the heat exchanger, or thru the opening in the shroud if the fan is still out, and use a hair dryer or a low flow of compressed air to verify that they are both opening. On several occasions I have found one bound and had to loosen the cover, adjust it and the gasket, and try again. This might not have been required on the originals but these are reproductions and that may affect their weight and operation.

Amazon has several inexpensive endoscopes if someone needs one. You can't easily see the flaps in operation without one.

$49 dual lens front and side with camera, sd card and more
https://www.amazon.com/DEPSTECH-Industrial-Inspect...5&th=1

$19 needs smart phone or laptop. Single lens https://www.amazon.com/dp/B07PBF6DX5?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_9
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[Willin]

This is a good point!
My flaps were broken. So I fabbed some flaps out of license plate aluminum.
To test for function, I used air. I forget now if I used compressed air, or my shop vac. But blowing, or sucking, both ways through the shroud told me they were, indeed, flapping.
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73 bus. Org. 1700 with dual Weber 40 idfs, bus header with Empi qp muffler, CB magnaspark 2 " ready to run kit".

[SGKent]