Limit circuit fault furnace

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.

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 …It's been cold here in Indy the last couple of days (6 degrees Fahrenheit) but the furnace will not get above 67/68. Runs for about 5 minutes then cycles to the blower for a few minutes. Shit appears to be working correctly. I removed the main limit switch earlier today to see if it was dirty and I heard an audible click.Limit switch issue with Nordyne furnace...need help. Model# GL1RA 072N - 16B. Serial# GLD070506859. Limit switch was opening after running for nine minutes. Limit was opening slightly prematurely so we replaced with a new one...Filter was filthy...changed filter, new switch still opening...confirmed all registers were open and inspected coil ...Circuit Breaker/Fuse: Most likely, either the electrical system providing your furnace's power has shorted or the power switch has blown. Try resetting your furnace's circuit breaker. If it has blown, you will need to replace it. Igniter: The furnace's igniter might either be cracked or faulty.The circuit board indicated a no.1 fault (Air flow/Limit Fault). I dismantled the furnace blower (from the outside, without removing the furnace) and discovered that the problem was the sail switch was improperly placed, and rubbing against the outside housing (sticking, in other words). I fixed that, and all is good now.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: ...Carrier Furnace has code 33- limit circuit fault - very strong burning rubber smell. Furnace from 07. Last year it broke and had major parts replaced from home warranty company. Guy said it's basically brand new. Well looks like it lasted halfway through winter again.

But if i turn the power off then on, at first its just the blower, then the gas sound then the flames are on for maybe 5 minutes when it kicks off the light starts blinking and it says "limit circuit lockout- lockout occurs if the limit, draft safeguard, flame rollout, or blocked vent switch (if used) is open longer than 3 minutes.Set a multimeter to test for resistance (ohms). Touch each tester probe to one of the switch terminals. The pressure switch tester should read 0 or close to 0 (indicating no resistance). If the reading is higher, the switch has failed and must be replaced by a qualified technician.Aug 16, 2023 · 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, orfailed ... Old 75% 120,000 BTU input furnace has an output of 90,000 BTU. If its replaced with the SAME SIZE 95% furnace, that furnace would have an output of 114,000 BTU. In this case, the new furnace is now oversized by 20%. A proper install would be to reduce the size of the new furnace to either the 80,000 or 100,000 furnace.Limit switches don't usually wear out by themselves. They are a safety device that is never actually intended to be used. So it should last the life of the furnace. Even if they do get a lot of use (if an air filter gets neglected and clogged), the airflow issue can be corrected and the defective limit switch can be replaced.* Update: I replaced the filter and that fixed the problem. Hope this helps and saves you some money.Here is short video showing how to read the blinking e...

Millions of Americans rely on furnaces to stay warm and comfy when the weather’s cold. Many homeowners, however, balk at the cost of keeping these major appliances running. Althoug...The limit circuit is a safety feature that is designed to prevent the furnace from overheating. It consists of a sensor and a switch that monitors the temperature inside the furnace and shuts off the furnace if the temperature exceeds a certain level.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 cycleMy Carrier Performance 96 series furnace (similar to the 59TP6 currently shown on Carrier's website, but I don't have the exact model number in front of me) has been showing codes 13 ("Limit Circuit Lockout") and 33 ("Limit Circuit Fault") intermittently for the last two years, but several repairmen have come and been unable to find anything wrong.Tempstar furnace is throwing a limit circuit fault code (4 flashes), working through troubleshooting. Installed in 2016 to new build home in southern Ontario, Canada. -Replaced filter -Ran without filter -Made sure all vents are open and unobstructed -Cleaned flame sensor rod -Tested limit switch for continuity -Tested limit circuit on board ...

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Electronic Condensing Furnace Troubleshooting Guide NOTE: Read the entire instruction manual before starting the Fault Code 13—Limit Switch Lockout..15-16 Fault Code 14—Ignition You have a short circuit in limit switch circuit.Gas and Oil Home Heating Furnaces - Goodman Furnace Open High Limit (code: 4 blinking lights) - Hello, I have a Goodman Furnace, model GDH80703AXAC, it was installed a little under a year ago. It worked fine for the first year and fine so far for this year. Until about 2 days ago. The burners went out, and when IPossible 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 code 13 is a limit circuit lockout error, which means that the furnace has tripped its limit switch and will not reset until it has cooled down. This can …

Reason 7: High Limit Switch & Roll-Out Switch. A blinking red light may also indicate issues with the high limit switch or roll-out switch. The high-limit switch monitors the temperature of the heat exchanger, while roll-out switches monitor for heat in areas where it should not be present. Solution: Inspect and clean or replace the switches as ... 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. user_12345a said: Use a meter to see if the limit is stuck open - with power off and furnace is cool, disconnect the wires to the high limit, set meter to ohms and check -> it should read 0 ohms or very close to that. If it's open or reads significant resistance, replace the limit with identical goodman part with same readings.MPGA075B3B LED FAULT CODE FLASHES 4 TIMES (HIGH LIMIT CIRCUIT OPEN I CHANGED THE AIR - Answered by a verified HVAC Technician We use cookies to give you the best possible experience on our website. By continuing to use this site you consent to the use of cookies on your device as described in our cookie policy unless you have disabled them.Steps To Manually Reset A Furnace Limit Switch? Cut the power. Locate the panelboard and turn off the furnace's power supply. It eliminates the possibility of electrical mishaps. Toggle the breaker switch labeled "Heating System" or "Furnace" towards the 'off position. Access the control panel of the furnace.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.Turn off the furnace power and repair a short or replace the pressure switch. 4. Read three LED flashes to mean your furnace has an open pressure switch circuit or it has an induced draft blower operating. Check the pressure switch hose of your furnace for blocks or an improper connection.When a heat call ends, my furnace control board (Emerson 50M56-495) is supposed to keep the inducer fan on for a little bit (maybe 10 seconds) and keep the circulator fan on for another minute or so (it can be set to 60, 100, 140, or 180 seconds via dip switches) to dissipate the heat. That is not happening currently. When a heat call …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)Some of the most common problems with Rheem furnaces include: No heat or insufficient heat. Frequent cycling of the furnace on and off. A blower that runs constantly. A noisy furnace that rattles of bangs. A pilot light that won't stay lit. An electronic Igniter that won't spark. Thermostat problems.Nordyne Furnace "burner limit circuit open", during A/C operation [ 4 Answers ] Hi all, Hope this makes sense and required info is present. Any help or suggestions is appreciated, thanks. Furnace brand is Nordyne, about 3 years old, cooling portion model# of unit is JS3BA-036KA. This issue started last week.

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

In many cases the furnace model and serial number is printed on a sticker affixed to the side of the furnace cabinet. Amana (https://www.amana-hac.com) Technical Support Number: 866-616-2664 American Standard (https://www.americanstandardair.com) Technical Support Number: 800-945-5884Furnace 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 cleanTo 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 ...Learn how to troubleshoot an open limit fault on a furnace. These tips are for licensed HVAC technicians only. For more tips visit edgetekhvac.comprotection 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.A carrier furnace code 13 indicates that the limit switch is open. If the limit switch opens 5 times for at least 3 minutes each time during 1 thermostat cycle this will trigger the status code 13. This status code is associated with overheating within the furnace causing the limit switch to open. With that said, there are a few things that can ...The FP1 thermistor temperature must be below the selected low temperature limit setting for 30 continuous seconds during a compressor run cycle to be recognized as a FP1 fault. JW3 Clipped = 10 deg. Unclipped = 30 deg. The FP1 input is bypassed for the initial 120 seconds of a compressor run cycle. FP1 is set at the factory for one try.The code thrown was limit circuit lockout. When the technician was here he asked a lot about if all my registers were open which was an easy yes and diagnosed that if my furnace has been tripping a lot I should get the switch replaced. He set my furnace to only use first stage heat and left getting me that part ordered.Model number 58MTA080-F-12112. It is giving off code 33 which is limit circuit fault. The funny thing is that the house still heats up. I ran the furnace all winter last year like this. Very rarely do I get a lock out. Last night I got a 14 code ignition lock out. I reset the furnace and went to sleep.Settings Open Close Application Nordyne Part # Switch Type -0.55 -0.75 80+ upflow 632212 atm.-single port (NO) -0.55 -0.75 80+ downflow 632212 atm.-single port (NO) *G6RD vent pressure switch is normally closed Table 7. Page 34 Check-out Procedure: 2. Connect a Differential Pressure Gauge or Inclined 1.

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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 ...1517 posts · Joined 2009. #4 · Jan 28, 2012 (Edited) Code 31, 32 refers to the pressure switch not closing. Code 42 refers to the inducing/draft motor not coming up to speed. If I remember correctly you may have a variable speed draft motor. I would suggest that the flue be disconnected from the draft motor and try a call for heat.6. Goodman Furnace Makes Strange Noises. Mechanical noises, such as clicking, may be due to loose screws or broken parts inside your Goodman furnace. Electrical noises, such as humming or buzzing, are generally due to a loose component on the control board, wiring issues, and other failing parts of the circuit.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 ...Status Code 13 - Limit Circuit Lockout. 16. Status Code 14 - Ignition Lockout. 17. ... Limit Circuit Fault. 26. Status Code 34 - Ignition-Proving Fault. 28. ... DIRECT VENT 4-WAY MULTIPOISE MODULATING CONDENSING GAS FURNACE WITH PERFECT SENSE PERFECT HUMIDITY. Brand: Bryant ...The blower below could be the cause of limiting out of the furnace. This is the result of no filter in the furnace or a plugged filter. It requires thorough cleaning by disassembly and cleaning the blower wheel with strong detergent or power wash. The motor (center) should not get water on it. Clean it with a brush.Blower is on after start-up (gas furnaces) / Blower calibration lockout (electric furnaces) 13: Limit circuit/switch lockout: 14: Ignition lockout: 21: Gas heating lockout (gas furnaces) / Invalid model selection (electric furnaces) ... Low-pressure switch fault (gas furnaces) / Low voltage detected (electric furnaces)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 ...The flame rollout or rollout switch detects an overheating issue in the furnace combustion chamber. In this case, it instantly shuts its system to stop the gas supply and let the flame go off. Typically, you'll see this device nearby the burners or burner compartment. In contrast, furnace high limit switches have a probe sensor to detect high ...Step 1. Locate the LED display panel for the furnace. This panel provides essential information. Once you locate it, ensure that the green light is on to indicate the board is functioning and the furnace has power. Alternatively, check to ensure that the furnace is plugged in if the green light is not on, or that a fuse is not blown in the main ...I have a Frigidaire furnace model #FG7TC O8OD-VC and the flashing green and no red lights tell me I have a "open limit switch fault". Outside temp. 26 inside 63. started last night.. green light and r … ….

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 ...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.What the Limit Switch Does – Safety and Comfort in One Switch. The furnace high limit switch helps to ensure your safety and the comfort of your home. Pretty handy for a part that costs as little as $4. It senses the furnace temperature in the plenum, and tells the blower fan to turn on and off as needed, according to pre-set temperature ...In many cases the furnace model and serial number is printed on a sticker affixed to the side of the furnace cabinet. Amana (https://www.amana-hac.com) Technical Support Number: 866-616-2664 American Standard (https://www.americanstandardair.com) Technical Support Number: 800-945-5884Circuits can be a great way to work out without any special equipment. To build your circuit, choose 3-4 exercises from each category liste. Circuits can be a great way to work out...Furnace Limit Circuit Fault. Web if your furnace is malfunctioning, the problem could very well be a faulty limit switch, but since it's a safety device, it may be operating normally, and the culprit. Douglas, hvac technician hvac 3,131 hvac technician:OVERFIRE - 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.Bryant furnace code 33 (3 short flashes and 3 long flashes) indicate a limit circuit fault – this means that the high limit switch has been open. Such an error can appear if there’s a lack of airflow; changing the filter, opening the vents, and getting rid of any obstructions in the duct should help. Limit circuit fault furnace, 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 ..., With the fault you are seeing it could be low DC voltage, faulty sail switch, limit switch or circuit board. Make sure you have good DC battery voltage, if the voltage is below 12 volts the fan can slow down and not spin fast enough to close the sail switch., 1. Code 33 - Limit Circuit Fault. This code often implies that the furnace has exceeded its safe temperature limit. Overheating can lead to other components' premature wear and tear, and it may even pose a fire risk. It's advisable to turn off your furnace and contact a professional as soon as possible. 2. Code 13 - Limit Circuit Lockout, Plus I can repair anything myself as well and have all the tools, so no need for a tech and the cost of one. Here are my specs: Infinity Carrier. Furnace: 58MVC080-F-10114. software version: CEDR131312-13. SYSTXCCITC01-B. software version: 131626-03.60. Lennox PureAir model: PCO14-23. Thanks in advance!, , Bryant Furnace parts on amazon→ http://amzn.to/2wY6FDfThere are several troubleshoots the furnace sticker lists that might be the problem. I point out severa..., Tip: the chances are high that the furnace won't start operating immediately. Give the system at least a few minutes. You can also go to the main electrical panel and find your furnace's circuit. The circuit breaker might have tripped, so flip it to 'on'. If the furnace continues to trip the circuit breaker - better call a ..., 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., Electric furnaces consist of several key components that work together to produce heat. One important step in operating an electric furnace is to switch it on. These include the electrical system switch, heating elements, blower motors, and thermostat settings step. Each step plays a crucial role in the operation of the furnace., Carrier Furnace has code 33- limit circuit fault - very strong burning rubber smell. Furnace from 07. Last year it broke and had major parts replaced from home warranty company. Guy said it’s basically brand new. Well looks like it lasted halfway through winter again., Limit switch issue with Nordyne furnace...need help. Model# GL1RA 072N - 16B. Serial# GLD070506859. Limit switch was opening after running for nine minutes. Limit was opening slightly prematurely so we replaced with a new one...Filter was filthy...changed filter, new switch still opening...confirmed all registers were open and …, 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 ..., Carrier 8000 VS has a limit circuit fault. We have been dealing with a lot of issues where furnace shuts off. Tech - Answered by a verified HVAC Technician ... a Carrier 58 MVB080-F-10114 furnace. I keep having issues with it tripping on the flame rollout switch. I have had a furnace company come and check it out twice and they haven't been ..., Open Limit Fault Nordyne/Nortek Furnace Furnace Hi all! Looking for some advice for my model (KG7SA 108C - 35C1) Nortek 80+ single stage furnace. I had it running at a vacant home to keep it warm until the sale goes through, and stopped by to replace the air filter. When I got in, home was cold and the panel for the furnace said it was an open ..., My furnace is giving me an fault condition of limit circuit open or. Bryant furnace: bryant furnace limit switch locationHvac 4eaf b759 furnace Carrier comfort 92 furnace 33 limit circuit fault to 13 limit circuitLimit circuit fault, need second advice (carrier 58mvb)., My Carrier Performance 96 series furnace (similar to the 59TP6 currently shown on Carrier's website, but I don't have the exact model number in front of me) has been showing codes 13 ("Limit Circuit Lockout") and 33 ("Limit Circuit Fault") intermittently for the last two years, but several repairmen have come and been unable to find anything wrong., Always install a furnace to operate within the furnace's intended temperature-rise range with a duct system which has external static pressure within the allowable range, as specified on the furnace rating plate and OPERATIONAL CHECKS section of these instructions. When a furnace is installed so that supply ducts carry, Status codes 4 + 2. Inducer motor fault. Proper vent sizing; restricted vent; failed inducer motor; improper motor wiring; a blockage in the tubing to the pressure switch assembly. Status codes 4 + 3. The low or medium pressure switch is open while the medium or high-pressure switch is closed., Hvac 4eaf b759 furnaceMy furnace is giving me an fault condition of limit circuit open or Furnace limit circuit faultBryant furnace breakers datasheets. Ducane furnace model no. mpga075b3b led fault code flashes 4 times highWe have a gas furnace & we believe that the limit switch is not working My furnace is not coming on. the power is working ..., Furnace Limit Circuit Fault. Web if your furnace is malfunctioning, the problem could very well be a faulty limit switch, but since it's a safety device, it may be operating normally, and the culprit. Douglas, hvac technician hvac 3,131 hvac technician:, CIRCUIT BREAKER. Page 4 G61MPV Gas Furnace The G61MPV category IV gas furnace is equipped with a two−stage, variable speed integrated control. This control ... to do so may cause erratic limit operation. This G61MPV furnace may be used as a high−static unit heater. The G61MPV may also be installed in an aircraft, From https://www.justanswer.com/ythiJustAnswer Customer: My carrier furnace is blinking code 13: limit circuit lockout.JustAnswer Customer: if i flip the pow..., For more technical tips, visit edgetekhvac.comThese technical tips are for licensed HVAC contractors only., The high limit is one of two switches found on the furnace limit switch. The other is the low limit switch. ... Deactivate the furnace: Turn off the power at the circuit breaker and turn off the gas valve. Note down the old switch readings: Take a picture of the readings on the switch using your phone. You'll need them to set the new switch., FIX: Review instructions to correct polarity. CODE: 1 + 2. PROBLEM: The blower is on after power up. 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., This is caused by a dirty filter, a dirty evaporator coil (number one reason if the evaporator is over 10 years of age), an improper rpm output or malfunctioning blower motor. The best way to go about testing the limit is to first find out what the limit cut off temperature is. On the limit it will have something like 140-20 or 160-20., 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 ..., How to diagnose a faulty furnace limit switch (a comprehensive guideFurnace limit switch troubleshooting [in 10 easy steps] I've got a open limit switch fault indicator light on my furnaceI need help with a carrier furnace 58sta090-10114. i have a limit. My furnace is giving me an fault condition of limit circuit open orI need help with a ..., My Carrier Performance 96 series furnace (similar to the 59TP6 currently shown on Carrier's website, but I don't have the exact model number in front of me) has been showing codes 13 ("Limit Circuit Lockout") and 33 ("Limit Circuit Fault") intermittently for the last two years, but several repairmen have come and been unable to find anything wrong., Kenmore Capacitor Parts Kenmore Chassis Parts Kenmore Circuit Board & Timer Parts Kenmore Compressor & Sealed System Parts Kenmore Deflector & Chute Parts Kenmore Diode, ... Shop by Popular Kenmore Furnace Models. 867.740290 867.740291 867.740293 867.741010 867.741090 867.741434., 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 ..., Settings Open Close Application Nordyne Part # Switch Type -0.55 -0.75 80+ upflow 632212 atm.-single port (NO) -0.55 -0.75 80+ downflow 632212 atm.-single port (NO) *G6RD vent pressure switch is normally closed Table 7. Page 34 Check-out Procedure: 2. Connect a Differential Pressure Gauge or Inclined 1., If the limit switch tests OK; or you've replaced it and still have the issue, you'll want to focus on the thermostat. From your description, it sounds more like a problem with the thermostat. Most safety mechanisms in furnaces do not let the furnace fire if there's a fault, so if you're getting flame I would not suspect a limit switch. I would ...