Furnace repair in Pennsylvania

A furnace has a short list of things that commonly go wrong, and a good diagnosis works through them in order rather than guessing. Here is what we actually find on Pennsylvania service calls.

The furnace runs but blows cold air

On a modern gas furnace this most often means the burners are lighting and then shutting down, while the blower keeps running. The classic cause is a dirty flame sensor — a thin metal rod that confirms there is actually a flame. As it oxidises it stops reading the flame properly, so the control board shuts the gas valve off within seconds as a safety measure. It is a cheap part and often only needs cleaning.

The other common version is a furnace in continuous fan mode, which blows room-temperature air when there is no call for heat. That is a thermostat setting, not a fault.

No heat at all

Working from the most common down:

• Hot surface igniter failure. These are brittle silicon carbide or nitride elements that crack with age and thermal cycling. When one fails the furnace tries to light, gives up, and locks out.
• Blocked intake or exhaust. High-efficiency furnaces vent through PVC pipe out a sidewall. Snow drifts, ice build-up, leaves and nesting birds all block them, and the pressure switch then refuses to let the furnace fire. This is a genuinely seasonal Pennsylvania problem and it is worth checking your vent terminations after heavy snow.
• Failed inducer motor or a cracked pressure switch hose.
• Tripped limit switch from restricted airflow — usually a filter that has not been changed, or closed supply registers.
• Gas valve or control board failure. Less common, more expensive, and worth confirming carefully before replacing.
• Thermostat or wiring. Including dead batteries, which we would always rather find than not.

It turns on and off every few minutes

Short cycling is the furnace reaching its safety limit and shutting down before the house is satisfied. Restricted airflow is the leading cause, which is why a one-inch filter left in for a whole season causes so many winter calls. It can also be an oversized furnace, a failing limit switch, or a flue problem. Short cycling wears out ignition components quickly, so it is worth fixing promptly rather than living with.

Noise

A screech on start-up usually points at the blower motor or its bearings. A rumble after the burners light can indicate a dirty burner or a combustion problem. A loud bang on ignition — delayed ignition, where gas builds briefly before lighting — needs attention promptly; it is hard on the heat exchanger.

Oil furnaces

Oil heat is still in service across north-eastern and rural Pennsylvania, and oil furnaces fail differently. The service list is the nozzle, electrodes, cad cell flame detector, fuel pump pressure, oil filter and chimney draft. A sooted or sulphured heat exchanger and a clogged filter after a fuel delivery stirred up tank sediment are both routine findings.

Cracked heat exchangers

This is the one furnace fault we will not repair. The heat exchanger is the barrier between combustion gases and the air you breathe, and when it cracks, the correct answer is replacement rather than a patch. We will show you what we found and explain how we confirmed it. If a contractor condemns a furnace without showing you anything, get a second opinion.

Repair or replace

Most furnace faults are worth repairing — igniters, sensors, capacitors, switches and motors are all ordinary parts. Replacement becomes the better value when the heat exchanger has failed, when a furnace past fifteen or twenty years needs a major component, or when a third repair lands in the same season. We quote the repair first and let you decide, and we will tell you when we think the repair is the wrong spend.