I get 4 blinks it say open limit switch what does that mean

Count the blinks in between pauses. On the door of the furnace will be a legend that tells you what that number of blinks mean. For instance 3 blinks may mean open limit switch or pressure switch failed to close, something like that. Post here what it tells you then we can help.

On - OK
1 Blink - Ignition failure. Check Gas flow, gas pressure, gas valve, flame sensor.
2 Blinks - Closed pressure switch. Check pressure switch (stuck in closed position).
3 Blinks - Pressure switch - failre to close. Check venter, pressure switch, vent blockage.
4 Blinks - Open limit switch. Main limit or aux limit are open. (My comment - Means overheating in chamber. Often result of blocked intake air. Bad filter. In my case, plastic wrap had been sucked into the intake. )
6 Blinks - False flame sensed. Check sticking gas valve.
Rapid continuous blinking - Incorrect twinning, incorrect primary polarity. Reverse transformer secondary leads, reverse primary wires.

Closed pressure switch can be from dirty combustion vents, bad chamber pressure - like missing screws, maladjusted gas pressure, failing pressure switch, loose hoses, moisture in the hoses or fan blades The switch need to be closed to ge the unit to work

TRI-COLOR (DSI LED) DIAGNOSTIC TABLE
No. of Red BLINKS
1 Flame sensed when no flame should be present
Verify the gas valve is operating and shutting down properly. Flame in burner assemble should extinguish promptly at the end of the cycle. Check orifices and gas pressure.

2 BLINKS Pressure switch stuck closed/ inducer error
Pressure switch stuck closed. Check switch function, verify inducer is turning off.

3 BLINKS 1st-stage pressure switch stuck open/inducer error
Check pressure switch function and tubing. Verify inducer is turning on the pulling sufficient vacuum to engage switch.

4 BLINKS Open limit switch Verify continuity through rollout switch circuit.

5 BLINKS Open rollout/open fuse detect Verify continuity through rollout switch circuit, check fuse.

6 BLINKS 1st-stage pressure switch cycle lockout If the first stage pressure switch cycles 5 times (open, closed) during one call for heat from the thermostat the control will lockout.Check pressure switch for fluttering, inconsistent closure or poor vacuum pressure.
7 BLINKS External lockout (retries exceeded) Failure to sense flame is often caused by carbon deposits on the
flame sensor, a disconnected or shorted flame sensor lead or a
poorly grounded furnace. Carbon deposits can be cleaned with
emery cloth. Verify sensor is not contacting the burner and is locatedin a good position to sense flame. Check sensor lead for shortingand verify furnace is grounded properly.

8 BLINKS External lockout (ignition recycles
exceeded where flame is established and then lost)Check items for exceeded retries listed above and verify valve is not dropping out allowing flame to be established and then lost.

9 BLINKS Grounding or Reversed polarity Verify the control and furnace are properly grounded. Check and reverse polarity (primary) if incorrect.

10 BLINKS Module gas valve contacts energized
with no call for heat Verify valve is not receiving voltage from a short. If a valve wiring is correct and condition persists, replace module.
11 BLINKS Limit switch open - possible blower
failure overheating limit Possible blower failure, restricted air flow through appliance or duct work. Verify continuity through limit switch circuit and correct overheating cause.

12 BLINKS Module Ignitor contact failure Fault code indicates the module ignitor contacts are not functioning
properly. Replace module.Solid Module - internal fault condition Module contacts for gas valve not operating or processor fault.
Reset control. if condition persists replace module.
3 double 2nd-stage Pressure Switch Stuck Open/Inducer Error
Check pressure switch function and tubing. Verify inducer.

Hi,
The 4 blinks means that the high limit switch or the regular limit switch are tripped... try to find the high limit switch... it is usually near the blower...there will be a red reset button in the center of it... push it in and the unit should work again...
if the regular limit switch is kicked you may have to replace it for the unit to work again...
This often happens after a power failure if the unit was running at the time of the failure. If you did not have a power failure, then find out why the limit switch kick out...

Here is a tip that will help you try to figure out why yourfurnace is not working.

BasicFurnace or Heating System Troubleshooting

heatman101

Hello, that code states that the limit switch is open on the Furnace, a limit switch opens when airflow is not adequate. Reason for this are dirty air filter, dirt on blower wheel, blower motor not running at proper speed, or blower motor not running at all. Anything that restricts the airflow over the heat exchanger will cause this switch to open. Let me know what you find and I will be glad to assist you further.

a limit open is saying that your furnace is over heating. a few things could be wrong. dirty filters, blocked air return or closed vents. the roll out switch,if your furnace has one , is also in this loop .it normaly will be needed to reset and is on top of the roll out sheild in the burner compartment. call a repair company if this is the problem.

Spill limit switch indicates that exhaust from the unit was prevented from going into the chimney. This can be a serious problem best left to a Pro.

4 blinks indicates a failure at the high limit switch. This switch is usually located on the heat exchanger face plate and has two wires going to it. Usually it fails because the furnace has over heated. The most common reasons are a plugged filter or coil that is limiting the airflow over the heat exchanger. Turn off the power to the furnace, replace the filter, clean any coils in the plenum and verify that all the vents in the home are open. Then turn the power back on and see if it is fixed. :)
If the above solution does not fix the problem, the limit switch itself may be bad from excessive heat. Replace it with a new one. Good Luck!

if this is an error code and you mean that the light blinks 4 times then it is the limit circuit. This could mean either the high limit or a roll out switch is open. the limit switch is right in the center of the furnace above the burner and roll out switches are probably somewhere around the opening of the burner. Follow the wires from the limit to find a roll out switch cause they are in line with each other and the rool out switch could have a button to reset it. However if the roll out is not tripped then you could need to change the limit. Only way to know is to check for continuity.

If you know where the high limit switch is you can always cut the two wires and wire them together causing the limit to close. But what you have to watch out for is why the high limit is not closing. That means in your return air either you have a dirty return air duct, dirty filter, or you don't have all your registors open to allow the heat to escape the heat exchanger. Just watch over riding the system. The high limit switch should either be on or behind the blower, in the middle of the system right under the heat exchanger. any other questions about hvac just ask.

David