I have a 24 year old 2.5 ton Carrier outdoor air conditioner unit that appears to be leaking coolant.  In 1999, we installed a new Carrier gas furnace (58YAV070-12) and evaporator coil (CD5AXA036017) and they seem to work fine.

I know that I need to replace the outdoor unit soon, but want to know if I can replace just the outside unit and match it to the existing indoor units.  Is that possible? Service techs say I should replace both, but I’d like some second opinions.

If it is possible to replace just the outdoor condenser, what are the drawbacks?  If the inside unit subsequently fails, what’s the worst case scenario? Could I just replace the indoor coil to match the new outdoor condenser or would I have to buy both a new condenser and a new coil? 

Thanks in advance for your advice.

George