Responded to a customer report of no cooling in Altadena California. Upon arrival, found their old Day & Night air conditioner low on refrigerant. Performed a leak search and pinpointed the leak on the schrader valve. Removed and replaced the valve, recharged the unit. Tested system after repairs and unit is functional again. Note: this is an old unit, 28 years, and should be considered for replacement. Will be submitting replacement option to customer.