An elderly couple was found dead in their sweltering South Carolina home as the heater reached a staggering 1,000 degrees Fahrenheit — leading firefighters to believe the machinery was ablaze at first glance.

The bodies of Joan Littlejohn, 84, and Glennwood Fowler, 82, were discovered by a police officer and paramedic Saturday after family members had not heard from the couple for three days and requested a welfare check, according to a police report.

The paramedic attempted to take the body temperatures of both Littlejohn and Fowler but their temps topped the measurable index of the device, surpassing 106 degrees F — well above 98.6 degrees, the standard body temperature of most adults.

Firefighters also responded to the scorching house where they estimated the temperature to be 120 degrees F — after the doors had been left open to the cold air for 20 minutes.

The smoke-eaters then headed to the basement of the Spartanburg home where they said the furnace looked like it was on fire. They measured its temperature to be approximately 1,000 degrees F before they shut it down, police said.

The couple had complained that their furnace and hot water heater were not working on Wednesday, so family members came to their home and “fiddled” with it until the pilot light on the heater turned on.

They left the home Wednesday and did not contact the couple, according to the police report.

The Spartanburg County Coroner is conducting an autopsy of both Littlejohn and Fowler to determine their exact cause of death.

Firefighters also checked the carbon dioxide levels in the home and did not find that they were above normal, police noted.

No foul play is suspected.

With Post wires.