Ducane furnaces may use gas or oil as a fuel depending on the efficiency of a specific model. Gas furnaces enjoy wide popularity due to their 95% AFUE efficiency which is very good for saving money on heating. Despite their impressive efficiency, they don’t produce much noise when blowing the air. Still, some customers may rarely face with certain malfunctions when the furnace just wouldn’t start or wouldn’t run the way it should. In fact, customers may fix some of them by themselves.
| SYMPTOM | PROBABLE CAUSE No pilot flame | ACTION |
|---|---|---|
| Pilot will not light. | Problem with SV9501 control/valve. | Check to see if main valve is turned “ON”. |
| Check pilot H.S.I for breakage. | ||
| Check pilot orifice for blockage. | ||
| Bumers will not ignite. | No 115 volt power to furnace. | Connect to power supply. Check fuse, wiring, or circuit breaker. |
| No 24 volt power to control circuit | Check transformer - replace. | |
| Miswired or loose connections. | Check fuse on fan timer board - replace. | |
| No gas at main burners. | Check all wiring and wiring connections. | |
| Flame rollout, blocked vent shutoff, or blocked drain safety switches open (activated). | Check to see if main valve is opening or turned “ON”. | |
| Problem with SV9501 control/valve. | Look for loose or broken wiring connections. If no deficiency is found, replace valve assembly. | |
| Check heat exchanger, venting system and condensate removal tubing for blockage. | ||
| Inadequate heating. | Furnace undersized for application. Gas input to furnace too low. Limit switch cycles main burners. Furnace cycles too often. | Replace with proper size furnace. |
| Check gas pressure at manifold. Clock gas meter for input If too low, increase manifold pressure, or replace with correct orifices. | ||
| Dirty air filters - clean and reinstall. | ||
| Blower speed too low - use faster speed tap. | ||
| Registers closed, restricted ductwork - open or remove restriction. | ||
| Check heat anticipator setting on thermostat - readjust | ||
| Aldehyde odors, (CO), sooting flame, floating flame. | Incomplete combustion - poor flame characteristics. | Check all screws around flue outlets and burner compartment - tighten. |
| LACK OF COMBUSTION AIR | ||
| Cracked heat exchanger - replace. | ||
| Overfired furnace - reduce input or change orifices. | ||
| Check vent for restriction - clean as required. |
| Problem | Solution |
|---|---|
| IF YOUR SYSTEM ISN’T RUNNING | Check to make sure your control or thermostat is set in the HEAT position. (You’d be surprised; often that’s the problem.) Make sure the temperature is set warmer than the current indoor temperature. If it isn’t, your system won’t know to provide heating. |
| Ensure your furnace’s power is on. Try turning the fan to ON using the fan switch on the control or thermostat to test for power to the furnace. | |
| Check the circuit breakers in your home’s circuit breaker box (electrical panel) to make sure they’re in the ON position. | |
| Check the furnace power switch to be sure it’s in the ON position (it looks like a light switch on a gray box located at the furnace). | |
| SYSTEM NOT HEATING ENOUGH: | Check the filter for buildup. If you have one-inch-thick furnace filters, a once-a-month change is recommended. Two-inch-thick filters – and other high-capacity pleated filters – usually only need to be changed every other month or less, depending on the type. If you don’t change it, the filter will block the proper airflow and strain your furnace. |
| Check all return air grilles to make sure they are not blocked. Return air grilles are larger and are located on a wall or the ceiling in newer homes. Older homes frequently have return air grilles on the floor. | |
| Check all supply registers to make sure they are open and blowing air. | |
| If you still don’t feel that wonderful rush of warmth throughout your home, it’s time to contact your local Carrier expert for service. | |
| OTHER SIGNS THAT INDICATE A SERVICE CALL MAY BE IN ORDER: | You hear your indoor-unit fan coming on, but the air from the registers isn’t warm or the fan is turning on and off more frequently than usual. NOTE: If your system control has a “Constant ON” feature, you will not always feel warmth, even though air may be blowing. |
| BEFORE YOU REQUEST A SERVICE CALL FOR YOUR VENTILATOR: | Check the main power disconnect switch. Verify that the circuit breakers are ON or that fuses have not blown. If you must reset breakers or replace fuses, do so only once. Contact your Carrier expert for assistance if the breakers trip or the fuses blow a second time. |
| Check for sufficient airflow. Check air filters for accumulations of large particles. Check for blocked exhaust air grilles or ductwork. Keep grilles and ductwork open and unobstructed. |
| Symptoms of Abnormal Operation | Fault Description(s) | Possible Causes |
|---|---|---|
| - Motor rocks slightly when starting. | - This is normal start-up for variable speed motor. | — |
| - Motor won't start. | - No movement. | - Manual disconnect switch off or door switch open. |
| - Blown fuse or circuit breaker. | ||
| - 24 Vac wires miswired. | ||
| - Unseated pins in wiring harness connectors. | ||
| - Bad motor/control module. | ||
| - Moisture present in motor or control module. | ||
| - Motor rocks, but won't start. | - Loose motor mount. | |
| - Blower wheel not tight on motor shaft. | ||
| - Bad motor/control module. | ||
| - Motor oscillates up & down while being tested off of blower. | - It is normal for motor to oscillate with no load on shaft. | — |
| - Motor starts, but runs erratically. | - Varies up and down or intermittent. | - Variation in 115 Vac to motor. |
| - Unseated pins in wiring harness connectors. | ||
| - Erratic CFM command from "BK" terminal. | ||
| - Improper thermostat connection or setting. | ||
| - Moisture present in motor/control module. | ||
| - "Hunts" or "puffs" at high CFM (speed). | - Incorrect or dirty filter(s). | |
| - Incorrect supply or return ductwork. | ||
| - Incorrect blower speed setting. | ||
| - Motor starts, but runs erratically. | - Stays at low CFM despite system call for cool or heat CFM. | - 24 Vac wires miswired or loose. |
| - "R" missing/not connected at motor. | ||
| - Fan is delay mode. | ||
| - Stays at high CFM. | - "R" missing/not connected at motor. | |
| - Fan is delay mode. | ||
| - Blower won’t shut off. | - Current leakage from controls into G, V, or W. | |
| - Air noise. | - High static creating high blower speed. | |
| - Incorrect supply or return ductwork. | ||
| - Incorrect or dirty filter(s). | ||
| - Incorrect blower speed setting. | ||
| - Excessive noise. | - Noisy blower or cabinet. | - Loose blower housing, panels, etc. |
| - High static creating high blower speed. | ||
| - Air leaks in ductwork, cabinets, or panels. | ||
| - "Hunts" or "puffs' at high CFM (speed). | - High static creating high blower speed. | |
| - Incorrect or dirty filter(s). | ||
| - Incorrect supply or return ductwork. | ||
| - Incorrect blower speed setting. | ||
| - Evidence of Moisture. | - Motor failure or malfunction has occurred and moisture is present. | - Moisture in motor/control module. |
| Problem | Cause | Solution |
|---|---|---|
| the furnace hot surface ignitor will not glow | If a furnace has a bad ignitor, loose wire connections, open limit switch, open rollout switch, open pressure switch or bad control board. This is what you might see in the furnace sequence of operation: Thermostat calls for heat when you turn up the thermostat | You should fist check to make sure you are getting 24 to 28 volts AC between the W (white) and C (com) terminals on your control board. |
| Make sure furnace blower door safety switch is pressed in when testing. If your control board has a fuse on it make sure the low voltage fuse is not blown. You might have to temporarily tape the blower door safety switch closed for temporary testing. If the fuse is blown on the control board nothing will happen. If the fuse is blown you might have a short in the low voltage thermostat wires. Check to make sure wires are not pinched anywhere | ||
| Draft inducer motor starts. | If draft inducer does not start then you either have a thermostat problem, thermostat wiring problem, loose wire connection, transformer problem, bad draft inducer relay on the control board or a draft inducer problem. Please make sure you can spin the draft inducer wheel freely. Sometimes if the draft inducer sits for a long time (like over summer) without operating the draft inducer wheel can become tight | |
| Pressure switch attached by a small plastic or rubber tube to the draft inducer senses the negative pressure produced by the draft inducer and closes | You should have 24 volts to ground across both terminals on the pressure switch. If pressure switch is not closed with draft inducer running check for a stopped up vent or a stopped up condensate drain line if you have a condensing furnace | |
| Limit Switch and rollout switch/switches should all be closed. | Press in on the reset button in the center of each rollout switch to make sure each rollout has been reset. You should have 24 to 28 volts from each terminal to ground. On most furnaces the ignitor will not glow unless all the safety controls (limit, rollout switch/switches, pressure switch) are closed. If a limit or rollout switch is open then you might have an over heating problem and a possible dangerous condition. If the Limit or rollout continues to trip I would strongly recommend calling an HVAC service company to check your furnace out | |
| Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound | If you hear a hissing gas sound with no gas ignition then more than likely either the ignitor is broken or the relay on the control board that sends power to the ignitor is broken. If the ignitor did not glow, the flame sensor (a small metal probe about 1/8″ in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace will shut down, and try ignition again. Most of the time after three tries the furnace will and go into a lock out condition until you turn your power switch back off and on again | |
| Your furnace will not ignite the gas to produce heat for your home | When a furnace has a bad ignitor what I see most of the time is the following sequence of operation: Thermostat calls for heat | |
| Draft inducer motor starts | ||
| Pressure switch attached by a small plastic or rubber tube senses the negative pressure produced by the draft inducer and closes | ||
| Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound | The ignitor did not glow, the flame sensor (a small metal probe about 1/8″ in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas | |
| My furnace’s ignitor does not glow? | This could be a pressure switch, limit, roll out switch, or furnace control board problem | f your vent piping is open, the hole in your draft inducer is open (not clogged with debris or water) and your pressure switch is working properly, then pressure switch will close the connection between two wires and send a signal to the control board |
| Draft inducer will not start, ignitor will not glow or gas valve will not open | Any combination of the above problem or problems could be caused by a bad furnace control board. I always troubleshoot and test the least expensive parts first, such as the pressure switch, limit switch and rollout switches to make sure they are all closed and operating correctly before I go to the control board. First, and most important things to remember is turn your electrical power off to the furnace. Most control boards are located in the blower compartment. Many control boards have a fuse located on them to protect the board from getting burned up if you have a short to ground. The fuse is usually a 3 to 5 amp fuse similar to the fuses that you might find in a car’s fuse box. | |
| Electric heat will not come on or fan will not come on | First and most important, Please make sure your electrical power is turned off before trying to repair or inspect any type of electrical appliance. | |
| Inspect the inside of the air handler or electric furnace for burnt wires | ||
| Check your breakers or fuses inside the air handler. Again, make sure your power is off. | ||
| If you still are not getting electric heat then you should test your sequencers to make sure they are working |
| Source | Causes | Correction |
|---|---|---|
| Thermostat | Thermostat in OFF or COOL | Switch to HEAT. |
| Thermostat is set too low | Turn thermostat to higher temperature. | |
| Safety Overloads | Burner motor overload tripped | Push reset button pump motor. |
| Primary control tripped on safety | Reset primary control. | |
| Auxiliary limit switch tripped on safety | Reset auxiliary limit. | |
| Power | Open switch | Close switch. |
| Blown fuse or tripped circuit breaker | Replace fuse or reset circuit breaker. | |
| Thermostat | Broken or loose thermostat wires | Repair or replace wires. |
| Loose thermostat screw connection | Tighten connection. | |
| Dirty thermostat contacts | Clean contacts. | |
| Thermostat not level | Level thermostat. | |
| Faulty thermostat | Replace thermostat. | |
| CAD Cell | Flame detector leads are shorted | Separate leads. |
| Flame detector exposed to light | Seal off false source of light. | |
| short circuit in the flame detector | Replace detector. | |
| Primary Control | Primary or auxiliary control switch is open | Check adjustment. Set the maximum setting. |
| Jumper terminals; if burner starts, switch is faulty, replace control. | ||
| Open circuit between disconnect switch and limit control | Trace wiring and repair or re- place it. | |
| Low line voltage or power failure | Call the power company. | |
| Defective internal control circuit | Replace the control. | |
| Burner | Blown fuse | Replace the fuse. |
| Binding burner blower wheel | Turn off power and rotate the blower wheel by hand. If seized, free the wheel or replace the fuel pump. | |
| Sized fuel pump | ||
| Defective burner motor | Replace the motor. |
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