Apc back-ups es 500 has a amber light and is constantly

SOURCE: green light flashes with a constant buzzing sound

It sounds like you need a new battery. If the APC is more than 3 years old, that is likely the problem. You can get a new battery from http://www.batteryinternational.com/apc-backups-es-be500u-ups-battery-ups-batteries-f2.html

SOURCE: hi in my apc es 500 the amber and green light is

Batteries in the UPS typically last 3 to 5 years and it depends upon several factors. including the number of times the unit must go on battery power and environmental conditions. There are usually several batteries in the UPS and while the battery voltage may show 13 volts, this may only be a float charge/voltage and a true indication of the battery voltage and condition requires the batteries to be tested under a load. There maybe one battery in a set of batteries that is faulty and causes the whole battery system to fail and indicate a battery fault.

These lower powered and cheaper type UPS are switch over types, when the mains supply fail, the UPS switches over to the battery and inverter in milli-seconds which then supplies mains power. A faulty inverter circuit and or flat batteries won’t deliver standby power when the mains supply fails.

SOURCE: APC Back-UPS ES 500: green light flashes&continuous warning tone

On this unit, the likely culprit is the battery and that it needs to be replaced.

With that, you may want to think about the pros and cons of replacement versus buying an entirely new unit.

This unit is a relatively low end ups and the surge supression uses MOVs that wear out with repeated absorption of energetic spikes. That's why the better (and higher cost) UPSs and surge suppressors don't use them. They're not really that good anyway due to their relatively high transient impedance. The better equipment uses a "transorb" -- basically a back-to-back high voltage zener diode optimized for low breakover impedance and high instantaneous power capability. Unless the transient exceeds the design parameters of the circuit, these do not wear out and do not degrade. That being said, I will assume that you would likely replace this unit with a similar one.
The flashing may not be the battery at all and may be the charging circuitry, thus your new battery may not live very long (half the life that you would expect.

Many batteries out there are refurbs and have issues as all used parts do.

If you contact APC, they will likely give you a 35% discount on purchasing a new product.

The difference in price in the battery replacement vs. ups replacement at this level may only be a few dollars more.

I promise that I am not a UPS salesman, I just deal with many on a daily basis; therefore I am giving my two cents to try to thelp you avoid problems a year from now.

Testimonial: "Outstanding answer with right amount of detail. I swapped battery with identical APC UPS that I have and vfd that battery was cause of warning tone."

SOURCE: red light and beeping

change the battery

SOURCE: APC 500 ES when i turn

the apc ups performs a self test when ever it is powered on.... it should complete the process in 10 to 20 second but if it does not, then there is something wrong with ups.. try to get it checked...