Arrived to no heat service call and performed system evaluation. Found unit not coming on due to no signal back to furnace from thermostat. Found varmint had chewed thru control wires leading to float switch. Replace wiring and tested unit. All amp draws in range. Blower and evaporator are clean. Motor amp draw in range. Temperature rise in range. Cycled unit multiple times to insure that all safeties are working and unit running as designed. System is heating at this time. Customer lives in rural area and spoke with homeowner he will install poison traps in attic.