# Lennox SLP98 pressure switch issues



## yuri

There have been a few failures of those switches but no more than average. The inducer needs to ramp DOWN to its lowest speed to calibrate the high and low aspects of the switch/venting. If it does not ramp down then it usually is the switch AND it is the dual pkg of switches unless you got the latest series which does not have a 3rd pressure switch. Have not had any problems with the latest version of it. THey also should be clearing the error codes off the board B4 they leave.


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## bcoop

I am having the same problem with my SLP98. I was able to get it fired up last night for about 3 hours, but the unit was off again this morning. There is no drainage issue and the vents are clear. The manual says to check the wiring for the pressure switch after clearing the vents. Is there anything else I can do before a tech arrives to eliminate everything besides a bad pressure switch?


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## petyanca

My slp98 behaves in a similar way: upon heat request the inducer spins up, and I can hear a click in the pressure switch. Then it spins for may be 20 sec, and slows down. When it slows down I can hear another click in the pressure switch. Then it stops and nothing happens. What can I do to fix this? The furnace is 14 months old. The furnace shows E228 error code on the thermostat.


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## yuri

call the installer or a certified Lennox dealer. parts should have a 10 yr warranty and there is nothing you can DIY with that furnace except check the vent pipes outside for blockage.


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## ahrens

Sounds like a bad pressure switch, they are finnicky things. Wouldve been two weeks ago now we installed a new carrier 60k btu furnace in a place ans the next day got a call saying it wont light. Was the pressure switch. Im surprised it took two different guys to figure it out though


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## mississippidave

I've had the had the same problem with my Lennox SLP98, but I have found something that worked for mine (which was installed in Nov. of 2011.

But first, the setting. Just after midnight on Christmas morning 2014 I was still up wrapping presents when I notice the air temp was cooler - checked the furnace and E228 flashing. Began the on and off every 10 minutes or so. Every Calibration cycle ended with E228. It was Christmas and a big snowstorm was on the way. No way I'm getting a serviceman on Christmas Day. So, I'm left to my own witts, and its either try the witts or have a cold family.

After checking to be sure there were no obstruction in the exhaust or intake or drainage (both ends of each and ShopVac-ing the pipes and tubes to be sure), I commenced my last ditch effort. I turned the furnace off, waited five minutes, turned it back on and waited for the CAL light on the control board (calibration cycle) to start. As soon as it started I began tapping the pressure switch very quickly with two screw drivers, one in each hand (I was a drummer in high school and have a drum set) and maintained the tapping throughout the calibration cycle....and Voila! The flame came on and the heat has been running nicely for 5 hours now. 

I know, however, that I will need to put in a new pressure switch, because this will happen again. A least I have a little time now to shop for a good price. I looked at the schematics/drawing and looked over the switch carefully. It doesn't look difficult at all to change. But if I change it, the 10 year limited warranty might be nullified if it is not already from the tapping. For today, I am warm on Christmas, and this advice is my gift to y'all. Hopefully, it will help a future reader to stay warm too. 
MERRY CHIRSTMAS Y'ALL!


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## mississippidave

Please forgive the typos in previous - I recently dislocated and broke my finger OUCH!


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## mississippidave

Oh, and thanks to you all for posting about this issue. Your generosity in taking the time to do so is greatly appreciated and is very helpful to many people. Thank you!


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## yuri

Yur Welcome. They won`t know you tapped it. May be cheaper to just buy the pressure switch from cozyparts.com than pay for a service call and labor for a dealer to change it. Make sure you have the COMPLETE model and serial number as there is a series number built in and they need it.


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## sparky90

[QUOTE

tapping the pressure switch very quickly with two screw drivers, one in each hand (I was a drummer in high school and have a drum set) and maintained the tapping throughout the calibration cycle....and Voila! [/QUOTE]

May I suggest drumming "wipe out" would be the best tune for success.


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## pingsusan

*Thanks A LOT!!!!!*



mississippidave said:


> I've had the had the same problem with my Lennox SLP98, but I have found something that worked for mine (which was installed in Nov. of 2011.
> 
> But first, the setting. Just after midnight on Christmas morning 2014 I was still up wrapping presents when I notice the air temp was cooler - checked the furnace and E228 flashing. Began the on and off every 10 minutes or so. Every Calibration cycle ended with E228. It was Christmas and a big snowstorm was on the way. No way I'm getting a serviceman on Christmas Day. So, I'm left to my own witts, and its either try the witts or have a cold family.
> 
> After checking to be sure there were no obstruction in the exhaust or intake or drainage (both ends of each and ShopVac-ing the pipes and tubes to be sure), I commenced my last ditch effort. I turned the furnace off, waited five minutes, turned it back on and waited for the CAL light on the control board (calibration cycle) to start. As soon as it started I began tapping the pressure switch very quickly with two screw drivers, one in each hand (I was a drummer in high school and have a drum set) and maintained the tapping throughout the calibration cycle....and Voila! The flame came on and the heat has been running nicely for 5 hours now.
> 
> I know, however, that I will need to put in a new pressure switch, because this will happen again. A least I have a little time now to shop for a good price. I looked at the schematics/drawing and looked over the switch carefully. It doesn't look difficult at all to change. But if I change it, the 10 year limited warranty might be nullified if it is not already from the tapping. For today, I am warm on Christmas, and this advice is my gift to y'all. Hopefully, it will help a future reader to stay warm too.
> MERRY CHIRSTMAS Y'ALL!


The above message worked for me as well. Thanks for posting.


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## dee2061

*bad pressure switch*

I have been having the same exact problem with my furnace. The last tech who came out seems like he knew what he was talking about and says it was a bad pressure switch. The first two techs found a couple leaves and believed that was problem. The last hvac company I used is a lennox dealer so the tech seemed much more knowledgeable on the unit. He said between 2011 and 2013 lennox was using faulty pressure switches in their furnaces that contained components made of tin causing them to fail after a year or two. I called Lennox directly but of course they will not tell you that. It's been almost 48 hours since the new pressure switch was installed and the furnace is still working. Keeping my fingers crossed.


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## Ian_R

*Faulty pressure switch*



dee2061 said:


> He said between 2011 and 2013 lennox was using faulty pressure switches in their furnaces that contained components made of tin causing them to fail after a year or two. I called Lennox directly but of course they will not tell you that.


I just had the pressure switch replaced in mine (installed 2012) this morning. The tech said he thought there should have been a recall on these but Lennox didn't/hasn't. Pretty much guaranteed to fail, he was surprised mine went this long before packing it in.


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## yuri

I think the tin story is a bunch of bullsheet. Almost all pressure switches are made by one company ( Honeywell ) as Tri delta went out of business. I doubt Lennox told a huge co like them to use tin. It is more a design concept/ fact that that furnace uses a very complex sensitive set of parameters for the setting of it. Has to do with the fact it is a modulating furnace and the couple different functions it has to do. Any tech that tells a customer his product is defective is plain stupid and would get fired in a minute where I work. Lennox probably tweaked the settings of it to make it more stable along with the programming of the circuit board/fail settings etc. Extremely complicated furnace but all mods are. I sell them and fix them and Lennox does not tell us what they do with every revision but it happens to every brand.


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## emunoz

I have the same issues with the pressure switches. Its really frustrating. I have very low confidence in the Lennox furnace. This is the fourth failure and its only 5 years old. I'm probably going to replace it with a Trane or Carrier this time. Hopefully the new one will last more than 5 years.


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## supers05

Usually you would make a new thread for your new issue, especially since this one is old. 

Are you needing help replacing the pressure switch or just complaining about it? 

Sent from my SM-G870W using Tapatalk


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## SeattleJohn

Thank you mississippidave for the awesome advice on playing the drums with 2 screwdrivers and a pressure switch. My SLP98 furnace when out last night and it was snowing this morning, so the temperature in the house was dropping fast. I had tried everything else and was getting close to the point where I was going to need to call someone out when I saw this post. My wife thought that I had gone crazy but drumming "wipe out" on the pressure switch did the job and the house is starting to warm back up.


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## kbaliey

I just wanted to add that the drum treatment worked for me as well - unbelievable. Used a letter opener and heavy duty laser pointer. I was ready to smash the furnace after having turned it off and on a hundred times for the fourth year in a row. Was about to make yet another service call and tried this as a last ditch attempt. Thank goodness! And thanks mississippidave.


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## shschaumburg

bad pressure switch
I have been having the same exact problem with my furnace. The last tech who came out seems like he knew what he was talking about and says it was a bad pressure switch. The first two techs found a couple leaves and believed that was problem. The last hvac company I used is a lennox dealer so the tech seemed much more knowledgeable on the unit. He said between 2011 and 2013 lennox was using faulty pressure switches in their furnaces that contained components made of tin causing them to fail after a year or two. I called Lennox directly but of course they will not tell you that. It's been almost 48 hours since the new pressure switch was installed and the furnace is still working. Keeping my fingers crossed.
On February 4, 2016 my high efficiency Lennox 3 year old furnace stopped heating my house, and the thermostat displayed Error Code 224 , which is Pressure Switch. It says in many online videos that the pressure switch shutting down is the sign that another problem exists in the furnace. What things should we check? What should a new Pressure Switch cost with professional installation after the installer picks up the part at the parts store? Was there a RECALL on this defective Pressure Switch? How do I contact Lennox to find out about any recalls?


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## coryville

I have been dealing with this issue since the unit was installed in 2010. I was getting E225 & E228 errors. Through research, I figured it was a pressure switch issue. I forget exactly how I came up with this fix, but it works for me every time. I gently remove the square tubing that goes into the front of the pressure switch and blow into it firmly like a straw (you might hear a slight click sound when doing so) and then replace the tube back on to the pressure switch. I either turn the heat back on from the thermostat or reset the breaker. It happens about 5 times or so over each NY heating season and has worked every time. I put some green masking tape on the tube so if it happens when I am away on business, my wife knows which tube to address. I should just replace the pressure switch, but who knows if a new one would even work properly. Hope this helps.


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## yuri

If you blow into it, it can bend or damage the membrane inside.

I would replace it. 

cozyparts.com for Lennox parts


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## Pete Giam

coryville said:


> I have been dealing with this issue since the unit was installed in 2010. I was getting E225 & E228 errors. Through research, I figured it was a pressure switch issue. I forget exactly how I came up with this fix, but it works for me every time. I gently remove the square tubing that goes into the front of the pressure switch and blow into it firmly like a straw (you might hear a slight click sound when doing so) and then replace the tube back on to the pressure switch. I either turn the heat back on from the thermostat or reset the breaker. It happens about 5 times or so over each NY heating season and has worked every time. I put some green masking tape on the tube so if it happens when I am away on business, my wife knows which tube to address. I should just replace the pressure switch, but who knows if a new one would even work properly. Hope this helps.


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## Pete Giam

I did what you explained. Pulled the square hose from front of pressure switch and blew slightly until I heard the click you mentioned. I blew into it a few times to hopefully kick some debris out. The furnace cycled and fired up the burner. Quick temporary fix. I will have the pressure switch replaced soon.


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## ajit01

I had the same issue with my slp98. I have been having the issue for years during winter. Removing the pressure switch and gently blowing through them always worked until this year. This winter it acted up again and no matter what I did E228 showed up. I removed the condenser pipe and let the water drain, cleaned the trap - to no luck. I had two service technicians look into it and did not have a clue. One suggested the installation was wrong and another one said the vent pipes need to be cleaned first. I ended up buying a pressure switch from a local lennox parts supplier and replaced it myself. It worked like a charm. The original pressure switches have been replaced with a newer design switch. I am hoping this does not cause the same problem as the older one.


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## suzanneferree

On the coldest night of this year with blizzard conditions across the Midwest this night of Dec 23, my 10 yr old SLP98 Lennox stopped. I couldn't get anyone to come out this late. It's below zero tonight. Inside temps were down to about 59 and dropping in my old drafty house. I didn't even know what a pressure switch in a furnace was. I had E225, E228 messages. After reading your generous tips, I got it up and going via turning everything off, then starting back up with the continual fast tapping on the switch. I'm hoping I can keep it going until they can get here tomorrow! Thank you, thank you, thank you from this cold homeowner in the Chicago area.


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## yuri

First of all everyone should check their vent pipes outdoors for any blockage/ debris like leaves or spiders webs/ icing/frost buildup or sucked in snow especially during a snowstorm. Also make sure there is no nearby snowbank or furniture or chairs etc which can cause the exhaust to recirculate into the intake and ice it up.

After yeah a rendition of Wipeout will work until you get new pressure switches. I am not sure if they changed the inside metal or guts but they do change the design of pressure switches from time to time and ALL brands do that. That is why all furnaces have a series # built into the model #.


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## brian.mauer

suzanneferree said:


> On the coldest night of this year with blizzard conditions across the Midwest this night of Dec 23, my 10 yr old SLP98 Lennox stopped. I couldn't get anyone to come out this late. It's below zero tonight. Inside temps were down to about 59 and dropping in my old drafty house. I didn't even know what a pressure switch in a furnace was. I had E225, E228 messages. After reading your generous tips, I got it up and going via turning everything off, then starting back up with the continual fast tapping on the switch. I'm hoping I can keep it going until they can get here tomorrow! Thank you, thank you, thank you from this cold homeowner in the Chicago area.


 I live in Iowa and have a Trane but besides that, our stories are similar! I kept getting a pressure switch fault code. Had an HVAC guy out this afternoon who replaced the blower motor ($500!.) I don't know sh#% about HVAC but have learned those switches can be very sensitive. Ayone have a short answer why a bad order blower motor would cause that particular fault code? It is working better than it ever has now so the expense is a bit more tolerable at least. Plus, my wife is no longer teetering on whether to castrate me. .


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## yuri

brian.mauer said:


> I live in Iowa and have a Trane but besides that, our stories are similar! I kept getting a pressure switch fault code. Had an HVAC guy out this afternoon who replaced the blower motor ($500!.) I don't know sh#% about HVAC but have learned those switches can be very sensitive. Ayone have a short answer why a bad order blower motor would cause that particular fault code? It is working better than it ever has now so the expense is a bit more tolerable at least. Plus, my wife is no longer teetering on whether to castrate me. .


They can slow down with age and not run fast enough to produce enough suction to close the switch.


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