Landlord is insisting we pay for a new HVAC (Commercial Property)

Location: California. Hi all, this is for my parent’s restaurant in California. The AC/heating unit is broken. It’s about 20 years old. Technicians have inspected it and told us it’s too old and the parts are difficult to find. The landlord is insisting that my parents are responsible for paying for a new HVAC system. Could you please offer me some advice? This is all the text in the lease related to repair:

“MAINTENANCE AND REPAIRS.

9.1 Excepting as hereinafter provided, Tenant shall keep the Premises, in

good condition and repair. If Tenant fails to perform any of the aforementioned

obligations, Landlord may, at its option, enter upon the Premises in order to place same in good condition and repair, and the cost, together with interest at the maximum legal rate per annum shall be due and immediately payable following

completion of Landlord's work.

9.2 Landlord shall keep in good condition and repair all portions of the

Premises not occupied by Tenant. Landlord shall have no obligation to make any

repairs until Landlord shall have received written notice of the need for repairs, and

Landlord shall not be in default of its obligation to repair provided Landlord

commences making same within a reasonable period following receipt of Tenant's notice and further provided that Landlord then proceeds with due diligence in

making repairs required of Landlord. Tenant waives the provisions of any law

permitting Tenant to make repairs at Landlord's expense.

9.3 Tenant shall maintain and keep in good repair:

(a) the interior of the Demised Premises, including walls, floors

and ceilings;

(b) all windows and doors, including frames, glass, molding and

hardware;

(c) all wires and plumbing within the Demised Premises which serve the Demised Premises as distinguished from the Shopping Center generally;

(d) all signs, air conditioning and heating equipment,

mechanical doors and other mechanical equipment situated on or in the Demised Premises or serving the Demised

Premises as distinguished from the Shopping Center

generally;

(e) those utility facilities serving only the demised “Premises”; and

(f) any other items not specifically set out in this Lease as Landlord's responsibility.”