Limit circuit fault furnace

Lack of airflow. Too many registers closed or blocked. Dirty blower assembly. Dirty evaporator coil. Not enough to return air. It could be a lot of different issues. Limit switches don’t usually wear out by themselves.

Limit circuit fault furnace. Raypak high limit 1 fault and 2 fault indicates that the High limit has exceeded the 135F temperature. The HL switches will open due to the raising temperature inside the inlet/outlet header up to 135 - 140 F. ... The heat exchanger is one type of metal alloy tube of the heater which transfers heat energy from a hot water circuit to the cooler ...

Blown Fuse. Power surges during a power outage can cause your furnace's fuse to blow. Examine the fuse box for any blown fuses and replace them if necessary. If you're unsure about doing this safely, contact a professional HVAC technician for assistance. Call us at (855) 345-6161 to schedule an appointment, ASAP!

To all technicians receiving a 33-Limit Fault Code. I has a major issue with a 59MN7 Modulating Furnace. These numbers were the result of running the system on High-Fire for 5 minutes. Excess Air%=40% - Carrier will tell you 40% Excess Air on a 59MN7 is not low and is in fact a great Excess Air Percentage. *Within 5min of run time the 33-Limit ...Jack. 33 LIMIT CIRCUIT FAULT - Indicates a limit, or flame rollout is open. Blower will run for 4 minutes or until open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33 continues to flash until blower shuts off. Flame rollout switch requires manual reset.Payne furnace is locked out with code 13, how do I reset it? Already pushed the button on the rollout switch and tested - Answered by a verified HVAC Technician. ... Hello. I need help with a Carrier furnace 58STA090-10114. I have a limit circuit fault code 33. ...05 - Heil Furnace Igniter. The igniter gets very hot and glows bright orange to light the gas burner. If the igniter fails, the gas won't continue to be ignited and the furnace may start then stop. To determine if the igniter is faulty, remove the igniter and inspect it for cracks. If the igniter is cracked, replace it.The pressure switch circuit is open or the induced draft blower is going. Check the pressure switch hose for blockages and ensure it is connected properly. Check the flue for blockages and look for loose wiring. 4 LED flashes. Your furnace's primary limit circuit is open, probably from loose wiring. You also might have a blocked filter.Jan 27, 2015 · For the sake of thoroughness, my explanation is long, but it should be an OK read, or maybe even interesting. I recently moved into a house which has a 3 year old KeepRite 100 KBTU/H residential furnace (N9MSB1002114A1 – 92% AFUE) that is constantly setting off the high temperature limit switch.

PROBLEM: LIMIT CIRCUIT FAULT - Indicates a limit, or flame rollout is open. Blower will run for 4 minutes or until open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13.24-vac terminal block on the furnace control (See Appendix A). This furnace can be installed with either a single-stage heat/cool or a two-stage heat/cool thermostat. This furnace is equipped with a manual reset limit switch in the gas control area. The switch will open and shut off power to the gas valve, if a flame rollout or overheating ...In this troubleshooting guide, we’ll be discussing carrier furnace code 33, the causes and the solutions to this status code. Code 33 on a carrier furnace indicates that This status code indicates the limit switch or flame rollout switch is open. This can be due to malfunctioning of one of the limit switches or overeating within the furnace.protection against short circuit or overload conditions. Anti-Short Cycle Protection - 4 minute anti-short cycle protection for the compressor. Random Start - 5 to 80 second random start upon power up. Fault Retry - in the fault condition, the control will stage off the outputs and then "try again" to satisfy the thermostat Y input call.The Trane S9V2 furnace can face specific challenges: Ignition Failures: Inspect the pilot light for proper functioning. Airflow Restrictions: Regularly clean or replace filters and check vents for obstructions. Control Board Issues: Diagnose problems like loose connections or burnt components on the control board.When your York furnace blinks red 4 times, take a look at the high-limit switch (similar to a pressure relief valve on an air compressor). In this case, it's usually open. This is often the result of a blown fuse, a malfunctioning pressure switch, or a dirty air filter. To remedy this, replace your air filter.

CODE: 3-3. RESULT: LIMIT CIRCUIT FAULT FIX: Indicates a limit, or flame rollout is open. Blower will run for 4 minutes or until open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13.No heat. Nordyne G7 fault, Open limit switch Fault. 1. When unit is off, both red/green leds lit (normal), 2. once thermostat temp is raised, fan starts, aux fan on exhaust starts, Green LED flashes, … read moreOVERFIRE - ensure furnace is not overtemperature (temp rise is above stated range). Check gas valve, proper orifice size, gas pressure, etc. Is Limit circuit open or opening and closing? Note: IFC Status LED should be blinking a Fault Code. Is the IFC sensing a good flame: NOTE: Flame sense light should be steady-on when burners are lit.According to the sticker inside my furnace access door a code 33 means a limit circuit fault caused by: Dirty and/or clogged air filter. No--I replaced my air filter on less than 3 weeks ago. Air filter is a larger Aprilaire filter and not the common 1" thick fiberglass strand type filter. Blocked vents or air returns.Limit circuit fault: either a limit or flame rollout is open: Check for: restricted vent; loose blower wheel; excessive wind; dirty air filter; or defective blower: Five LED flashes: An abnormal flame proving signal, the flame is likely proved while the gas valve is de-energized: Check for a leaky gas valve or a gas valve that is stuck open ...In this troubleshooting guide, we’ll be discussing carrier furnace code 33, the causes and the solutions to this status code. Code 33 on a carrier furnace indicates that This status code indicates the limit switch or flame rollout switch is open. This can be due to malfunctioning of one of the limit switches or overeating within the furnace.

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Blower Fault - Blower Remains Running: 61: Blower Fault - Blower Not Running: 66: ... Switch it to "auto" mode so the fan only operates when heating the furnace. Limit Switch Inspection: ... Try resetting your furnace's circuit breaker. Click Here for the detailed guide tp reset your furnace.Lack of airflow. Too many registers closed or blocked. Dirty blower assembly. Dirty evaporator coil. Not enough to return air. It could be a lot of different issues. Limit switches don’t usually wear out by themselves.Have a Payne gas furnace that stopped heating. My digital thermostat went blank and now the furnace only blows air. The red LED light in the furnace is blinking a code--- 3 slow flashes and then 3 fas … read moreI have a Nordyne G6RA mid efficiency furnace that was installed about 6 years ago. The problem is that the furnace continuelly kicks out on supplu air hi limit after about 5 min. The furnace then will … read more

Power ON Open all manual oil line valves. Close the line switch. Call for Heat Set thermostat (and limit) to call for heat. Thermostat circuit must be closed and power must be coming to black wire from limit circuit. Burner On The ignitor starts, followed 3 seconds later by the motor. (This delay compensates for sluggish start-up of some ACIn this episode of Repair and Replace, Vance shows how to replace the high limit switch in a gas furnace. The limit switch is a safety switch that monitors t...Heating systems are usually trouble-free and easy to maintain. Efficient operation is a function of good maintenance. Learn how to maintain a furnace. Advertisement Heating systems...Carrier Comfort 92 Furnace Error Code #13 and #33 Limit Circuit - YouTube. Chris Of All Trades. 7.47K subscribers. 98. 84K views 7 years ago. Fixing my carrier comfort 92 high efficiency...Page 9 33 LIMIT CIRCUIT FAULT – Indicates the limit, or flame rollout is open or the furnace is operating in high-heat only mode due to 2 successive low or medium heat limit trips. Blower will run at medium heat airflow for 4 minutes or until open switch remakes whichever is longer.Code 13, normally occurs as a result of code 33. In most cases, you will first spot code 33 which will stay for a while before turning to code 13. Code 33 on Carrier and Bryant furnaces is caused by a lack of airflow. If the issue is not resolved in time, it may develop to code 13, caused by safety lockout. Code 33 is a Limit Circuit Fault code.On the "first" call for heat, the high limit has cooled enough that the inducer comes on and the burner lights. When the high limit trips, the indoor fan and inducer continue to run until the limit cools, then lights the burner again. It continues this cycle until the thermostat is satisfied. I get 4 flashes on the board, High Limit, but the ...The furnace and house are only 3 years old He told me if that did not work then replace the circuit board. before i go out and buy a circuit board i was wondering if anyone can verify that is what the problem is. ... Limit Circuit Fault - 58STA110-22; Cookie Consent We use cookies to improve your website experience. To learn about our use of ...From https://www.justanswer.com/ythiJustAnswer Customer: My carrier furnace is blinking code 13: limit circuit lockout.JustAnswer Customer: if i flip the pow...

Hi. I just had a new Bryant Evolution 986T 80K BTU dual zone furnace (2 stage heat with variable fan + AC condenser) installed. The installer was an idiot. He originally installed Nest thermostats, no drain, crimped the water line, no p-trap, giant holes in the ducting, only had two small registers and a return in the second zone, etc.

Received 2 Upvotes on 2 Posts. Welcome to the forums!! An open limit switch is indicative of an over temperature condition and is usually caused by a dirty/clogged air filter, a blocked/restricted vent pipe, an obstructed return air duct, or a dirty/clogged a/c evaporator coil (if equipped). The most common cause is an air filter that has not ...5 Dec 2020 ... ... Lockout Limit Switch Open Limit Circuit Open Open High Limit Device Main Limit Open Primary Limit Switch Open How to Replace Furnace Filter: ...Payne furnace gets code 33 (limit circuit fault) and short cycles, but doesnt when the filter is removed. Furnace Hi, We have a gas furnace :Payne pg92sbs48080bb, which i understand to be 80000 btu. Live in a very cold climate in an older 2 storey 1850sq foot house, plus heated basement. We have used lower and lower rated filters, and now are ...FIX: Occurs if the unit is powered up during a call for heat or opens while the blower is on delay. CODE: 6 + 1. PROBLEM: Ignition lockout. FIX: Control will auto-reset after 3 hours. CODE: LED is off. PROBLEM: Secondary voltage fuse is open. FIX: Check whether the door switch isn’t closed or for a short circuit.Step 4. Check out the panel and look for the limit switch. Commonly, it's in a white or silver cover. Remove the cover to access the main body of the high-limit switch. The limit switch features two arms: one controls the low temperatures, and the other maintains the high temperatures. Another component between the two arms has to control the ...Limit Circuit Open or External Load On "W" ... FAULT CONDITION LIGHT FLAME ROLL-OUT SWITCH Refer to the Installation Instructions provided with the furnace for the proper heating and cooling speeds for your application. VENT SAFETY SWITCH (SELECT MODELS ONLY) For 80+ and 90+ Model FurnacesFIX: Occurs if the unit is powered up during a call for heat or opens while the blower is on delay. CODE: 6 + 1. PROBLEM: Ignition lockout. FIX: Control will auto-reset after 3 hours. CODE: LED is off. PROBLEM: Secondary voltage fuse is open. FIX: Check whether the door switch isn't closed or for a short circuit.This video provides step-by-step instructions for replacing the limit switch on Payne furnaces. The most common reason for replacing the limit switch is the ...Furnace shut off with "Limit Switch Lockout" (code 13). Works for 24 hours after a reset, power cycle. ... and then furnace does function throughout the day. If I just power cycle (and don't press the reset switch) I get a limit circuit fault, code 33. ... causing temp limit fault. After replacing the filter, cleaning out the condensate trap ...

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If we find a limit open, we will remove the limit, note the open rating (May be 180 to 210). Stick a metal probe thermometer in the chamber where we removed limit, call for heat and see if chamber is getting hotter than the rating on limit. If not we have a bad limit and it will need to be replaced. If it is getting too hot we have to determine ...Jan 22, 2024 · Frequency: Check and replace your furnace filters every 1-3 months, depending on usage and the type of filter. Benefits: Clean filters improve air quality and furnace efficiency while reducing strain on the system. Annual Professional Inspections. Scheduling: A certified HVAC technician inspects your furnace annually, ideally before the heating ... Samething happens. both inducer an blower motor starts after 5sec. Normally the inducer starts first and runs 30-60 seconds to purge the furnace of any fumes or gas. Then the pressure switch closes and the igniter and then gas come one. It sounds to me like one of your high temp limit controls is open.5. The Condensate Drain is Blocked. Finally, if your pressure switch is misbehaving, it may also be a sign that your furnace's condensate drain is blocked. Of course, this only applies to condensing furnaces. However, it's a pervasive problem because nearly 90% of all furnaces today are condensing units.Getting limit circuit fault on plus 80 furnace. 2010'ish. yes, flashing pattern indicates "Limit Circuit Fault". then - Answered by a verified HVAC TechnicianClosed vents, or possibly a bad limit switch. It could also be caused by an open rollout switch. You can try resetting the rollout switch (es) (see attached pic for typical). They are located just outside the burner chamber. Turn off the power then press the small button between the 2 leads to reset it. If it clicks you have reset it and the ...195 posts · Joined 2012. #8 · Nov 14, 2013. Make sure you are not getting a code 31, which is a pressure switch code.Alot of people read the code backwards.First number are the fast flashes and the second are the long ones.If you have one of the older metal pressure switches, wiggle the two wires alittle and restart the furnace.Code 13 should ...6 posts · Joined 2018. #1 · Nov 9, 2018. Hi guys, new member here and I'm so glad i found this forum. I am getting a code 13 (limit circuit lockout) on my carrier 58PAV070-08 This is after replacing both the limit switch and the roll out switch! I have tried letting it run for the 3 hour reset and resetting the roll out switch manually with ...heat. Abnormal events are 1) Limit circuit open during run, 2) Pressure switch open during run and 3) Flame failure during run. If one ... Lockout - communication bus / circuit fault. Check to assure no lead wire at Terminal 1 on thermostat block [unless control is in twinning application]. If present, remove ….

Page 56 TROUBLESHOOTING Green Amber Symptoms Fault Description Check Cautions LED Code LED Code LED Code •Temperature rise, duct static, •Furnace does not •Four •Open limit circuit, main •Confirm electrically safe gas pressure, burner alignment, operate, four Red •None •None repeating limit, aux limit, or roll out condition before ...Here are some common methods used to reset Bryant furnace codes:Using the SW-1 Button:a. Locate the control board on your Bryant furnace.b. Identify the SW-1 button, usually found on the control board.c. Press and release the SW-1 button.d. Wait for a few seconds to allow the reset process to complete.e.1. 1dl code on Goodman furnace: The 1dl code on a Goodman furnace indicates a limit switch lockout. This can be caused by a dirty air filter, blocked vents, or a malfunctioning limit switch. To fix this issue, try cleaning or replacing the air filter, ensuring proper airflow by clearing any obstructions in the vents, and checking and possibly ...Push the switch button off, and after a few minutes, push it on. You can push the reset button at least three times at 30-minute intervals. Proceed to the next step if your furnace is not responding. But before doing that, ensure the following. If using an electric furnace, ensure the power switch button is off.FIX: Occurs if the unit is powered up during a call for heat or opens while the blower is on delay. CODE: 6 + 1. PROBLEM: Ignition lockout. FIX: Control will auto-reset after 3 hours. CODE: LED is off. PROBLEM: Secondary voltage fuse is open. FIX: Check whether the door switch isn't closed or for a short circuit.Common causes are a bad blower motor or faulty blower wheel. To fix this, press the reset button on the side of the furnace. Solid Red Light. When your York furnace exhibits a solid red light, the control board has blown. To fix this, you must replace the entire control board. This will set you back around $500.Limit goodman high furnace open hvacBryant furnace: limit circuit lockout bryant furnace Top 4 reasons why a gas furnace short cyclesLimit circuit fault, need second advice (carrier 58mvb). Check Details. What does the primary limit switch on a furnace do? Hvac 4eaf b759 furnaceDucane furnace model no. mpga075b3b led fault …Four red flash: 24-volt fuse or high-limit switch open. This code indicates that there is an electrical problem or an overheating issue. This can damage your furnace components or cause a fire hazard. Check and correct the size of your ducting system and make sure it matches your furnace capacity.By interpreting these Trane furnace codes, users can swiftly identify specific needs, such as adjusting airflow or checking combustion, and address concerns to maintain optimal function. One amber flash: Call for cooling. Two amber flashes: Call for heat. Three amber flashes: Temperature fulfilled, burner ending cycle. Limit circuit fault furnace, For the sake of thoroughness, my explanation is long, but it should be an OK read, or maybe even interesting. I recently moved into a house which has a 3 year old KeepRite 100 KBTU/H residential furnace (N9MSB1002114A1 – 92% AFUE) that is constantly setting off the high temperature limit switch. I originally noticed this because I …, Open in the safety switch circuit (limit switch or flame roll out switch is open). • Unit sequence: • Green Light on, call for heat. Power exhauster cycles on. • Fan Motor Cycles on. Green light starts three flashes. • Possible cause: • Open or short in safety circuit (flame roll out switches some and some limit switches are manual ..., Ducane gas furnace three flashes code signals that rollout, aux limit switch are open or the fire pressure is low. Code-4 flashes. Ducane furnace 4 LED blinking lights to inform that the high limit switch is open. Code- 5 Flashes. It's not used. Code- 6 Flashes. The six flashes code informs that the pressure switch cycle is in a lockout. Code ..., The furnace will start up in either intermediate-, or maximum-heat. The furnace will transition and operate at minimum-heat or the calculated modulating rate after starting and operating for 45 seconds at intermediate-heat. The furnace control CPU defaults to minimum-heat on the first thermostat cycle and calculates the modulating rate, Payne furnace gets code 33 (limit circuit fault) and short cycles, but doesnt when the filter is removed. Furnace Hi, We have a gas furnace :Payne pg92sbs48080bb, which i understand to be 80000 btu. Live in a very cold climate in an older 2 storey 1850sq foot house, plus heated basement. We have used lower and lower rated filters, and now are ..., A 20-amp circuit is not limited by outlets, but by amps or watts used at once through the same circuit, and the circuit should not exceed 80 percent of its maximum load, according ..., CODE: 4 Flashes. RESULT: Limit circuit fault-a limit or flame rollout is open. Check for: restricted vent, proper vent sizing, loose blower wheel, excessive wind, dirty filter, defective blower motor, defective switch or connections, inadequate combustion air supply. , a heat cycle, both furnaces terminate the call for heat immediately. The only chance for blower mis-synchronization is if the blower off delays are set differently on the twins. If a twin fault occurs during high speed fan or continuous fan, both controls shut blowers off immediately. 6 flashes Limit Switch tripped 5 times during heat cycle, Code 13 – Limit Circuit Lockout This error code indicates that your furnace has shut down after repeatedly exceeding its safe temperature limit. This issue could be caused by a variety of factors including blocked air filters, faulty limit switch, or poor ventilation. , My Carrier furnace is blinking code 13: limit circuit lockout. If I unplug the furnace and plug back in with the thermostat set in the off position, I get a continuous red light, which the code reads Control has 24VAC Power. When I turn on heat, the heat blowers run, and then the fan comes on. When this happens the Code switches to 33., BCS said: So, my furnace suddenly stopped working. I have a trane xe 80 and my High temp limit switch open LED flashing light code appeared. I did some research and thought it was due to a clogged filter. I changed out the filters and it started up again. Thought that was the fix, but the burners went out and the same code again., Atwood furnace ignition lockout fault happens due to 3 possible reasons. Let’s learn the reasons in detail to solve the problem efficiently. 1. Faulty Flame Sensor. When you face a furnace lockout, check the condition of the flame sensor. This is the first thing you will need to do without fail. The faulty flame sensor is one of the common ..., Steps to Safely Reset Your Concord Furnace. Power Off: Begin by switching off the furnace. You can do this by turning off the switch located on or near the furnace or by flipping the appropriate circuit breaker in your home's electrical panel. Wait: Allow the furnace to sit without power for a few minutes., A ground fault occurs when any loose hot wire touches the furnace. The ground wire sticks with any conductive part of the furnace. So that it can take the electricity running on the body of the furnace. So if any hot wire touches the furnace, it can cause grounding faults. Also, this can cause a short circuit in the furnace., Push the switch button off, and after a few minutes, push it on. You can push the reset button at least three times at 30-minute intervals. Proceed to the next step if your furnace is not responding. But before doing that, ensure the following. If using an electric furnace, ensure the power switch button is off., Furnace bryant trane troubleshooting device condensing faultLimit circuit fault but house keeps warm Single stage furnace limit circuitDucane furnace model image0 hvac. Check Details. My furnace was attempting to cycle and i read to clean the flame sensor. I've got a open limit switch fault indicator light on my furnaceLimit circuit furnace ..., Bryant Gas Furnace 395CAV: Troubleshooting Guide Diagnostic of 31 Pressure fault code. Limit Circuit Fault. Furnace Bryant CONDENSING GAS FURNACE 340MAV User's Information. Carrier Bryant Payne HH18HA452 Roll Out Switch. Forum discussion: Product Description of [post_title] below:, The Bryant furnace code 33 indicates that a limit or flame rollout switch is open. This could occur due to Overheating in the furnace caused by insufficient airflow or the furnace operating only in high-heat mode. The blower will remain active for 4 minutes or until the switch resets, whichever duration is greater., 13,008. Post Likes. Originally Posted by The Gaffer. Have a customer with a ICP high efficiency furnace, throwing a 4 flashing light code, limit switch open. Here is what I have done so far (most as part of general service): Changed 2 x limit switch. Changed Pressure switch. Changed ignitor. Changed flame sensor., Oct 7, 2014 · code 13: limit circuit lockout code 33: limit circuit fault ... The most common cause of a limit trip is airflow thru the furnace. A dirty filter, clogged A/C coil ... , Page 59 TROUBLESHOOTING Green Amber Symptoms Fault Description Check Cautions LED Code LED Code LED Code •Temperature rise, duct static, •Furnace does not •Four •Open limit circuit, main •Confirm electrically safe gas pressure, burner alignment, operate, four Red •None •None repeating limit, aux limit, or roll out condition before ..., The EcoBee thermostat shows that it is still calling for heat. I opened up the panel and found that the green LED blinks when the system shuts down, indicating an "Open Limit Switch Fault" according to the manual I found (link above). It does not specify which limit switch is tripping, but given that it starts up again without need a reset, I'm ..., 83.6k 30 138 232. asked Dec 24, 2016 at 0:35. user64183. 3 1 1 3. If the blower is not running, the furnace will surely overheat. Get the blower running, and you shouldn't have a problem. - Tester101. Dec 24, 2016 at 15:49. Add a comment., If your gas furnace is not heating properly, the problem may be a faulty limit switch. In this video, we'll guide you through everything you need to know abo..., 20317 posts · Joined 2014. #2 · Nov 10, 2016 (Edited) You have to check the resistance of the limit when the furnace stops working, then figure why it's tripping. with a limit trip, the fan will continue to run but the burners and inducer will shut off. You can't check ohms with the limit switch connected btw - it will backfeed through the board., Furnace is not heating fault code: limit circuit open or external load on "W" I have reset the furnace, checked the supply air limit switch, checked the filter and cleaned the flame sensor Blower is on, thermostat is turned off, fan on auto. Contractor's Assistant: How old is your furnace? Is the air filter clean? 20 years old, checked last summer, filter is clean, Remove the cover (if one is present) to reveal the body of the switch. Set the fan limits: You'll see a temperature setting if you check between the two arms. This value controls the furnace's fan. It's the temperature at which the fan switch comes ON when the furnace is running. Set it to 105°F-115°F., My Carrier furnace is blinking code 13: limit circuit lockout. If I unplug the furnace and plug back in with the thermostat set in the off position, I get a continuous red light, which the code reads Control has 24VAC Power. When I turn on heat, the heat blowers run, and then the fan comes on. When this happens the Code switches to 33., Possible Causes for 4 flashes on a Goodman furnace. • Check filters andductwork for blockage.Clean filters or removeobstruction. circulator blower speed, orfailed circulator blower. • Check circulator blowerspeed and performance.Correct speed or replaceblower if necessary. • Misaligned burners, blockedflue and/or air inlet pipe, …, Carrier Furnace Limit Circuit Lockout [ 1 Answers ] My Carrier Furnace is continuously blowing and the heat doesn't work. The code was first, Limit Circuit Fault, tnen after changing the filter, it went to Limit Circuit Lockout -- and it is still blowing cold air. (Yikes!! It got down to 10 degrees outside), 3 S-16A Checking Air Circulator Blower Motor (Multi-Speed Ecm Motor) 4 Troubleshooting Chart. 5 Wiring Diagrams. Download this manual. Service and Troubleshooting. GMES80, AMES80, GCES80, ACES80, VMES80, VCES80 & Accessories. This manual is to be used by qualified, professionally. trained HVAC technicians only., 4 – LIMIT CIRCUIT FAULT: Indicates a limit or flame rollout is open. Blower will run for 4 minutes or until open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #7. If open less than 3 minutes status code #4 continues to flash until blower shuts off., In this episode of Repair and Replace, Vance shows how to replace the high limit switch in a gas furnace. The limit switch is a safety switch that monitors t...