Is there any AR regarding maintenance shop hours?

If the Commander signed it, you should just need to remind him/her of what (s)he signed.

These types of things are good for young Soldiers to know. But I want to caution you against trying to involve yourself, especially at your level. This is NOT your fight, this is your Shop Chief's fight.

Uh oh.... Maintenance is trying to get S-1 hours...

Usually an SOP is created because regulation does not cover it. The NCOIC/OIC should show the commander the memo he signed and ask where he is getting this new information. Maybe there is a conflicting SOP at the BDE level.

It depends on the "shop" and the "mission". Normally, any maintenance environment will work the maintenance personnel a maximum of 12-hours before giving them time off. Anything over 12-hours can result in mistakes due to fatigue. NOTICE I used the word "NORMALLY". You can start with: [AR 570–4 • 8 February 2006] 4–2. Availability factors
a. Standard Army availability factors will be used in manpower requirements determination programs to convert the required mission and workload essential work–hours into TDA, MOBTDA, and AUGTDA manpower requirements.
b. Tables of distribution and allowances (TDA) Army availability factors (AAF) are planning factors which prescribe the average number of hours per month which military personnel and U.S. civilian employees in TDA organizations are expected to be available for work on assigned jobs.
c. AAFs for foreign national employees will be developed by MACOMs based on current utilization, treaty agreements, and MACOM policy. They will be submitted for approval to Director, U.S. Army Manpower Analysis Agency, ATTN: SAMR–MAA, Fort Belvoir, VA 22060–5587.
d. Peacetime mission availability factors (PMAF) are the number of hours per month an MTOE Soldier is available to perform peacetime mission support. These factors will be used as necessary during manpower requirements determination studies, and application of manpower staffing standards to quantify the TDA requirements needed to accomplish workload beyond the capacity of the MTOE manpower authorized. Unlike the single 145–hour TDA availability factor, the MTOE availability factor varies by function.
e. AAFs and PMAFs are managed by the U.S. Army Manpower Analysis Agency, ATTN: SAMR–MAA, Fort Belvoir, VA 22060–5587. Procedures for using AAFs and PMAFs in the requirements determination process are provided in AR 570–5.
f. Tables 4–1 and 4–2 give the PMAFs and AAFs for peacetime.
g. Annual MOS availability factors (AMAF) for use in MARC studies are contained in AR 71–32.

There is a table which addresses the hours available.

Your shop works at the Commanders discretion. If your Commander required it your shop could work 24/7 or only three days a week. Your Commander signed the SOP but his Commander may have deemed that your shop is critical to the Brigade mission and so it requires the Brigade Commander approval. As a 94F your shop is most likely a key Brigade level asset and the shutdown affects much more than your company

Yep. 24/7.