# How to tell if Harman ESP probe is going bad? (on Accentra)



## Val (Jan 9, 2013)

I wrote about this before. My 2006 Accentra is reading room temperature "funny" on room temp. mode. It seems about 10 degrees off. I mean I have to set it over 80 degrees to get the room to 72. It never used to do this. Have run about 15 tons of pellets probably since I owned the stove. (I do clean the vent pipe and stove insides, too) Well, I finally took the esp probe out of the ehaust and cleaned it with a green scrubbie pad. It only had a very very thin layer of carbon on it and some ash. Well the stove still seems to do the same thing. If there is any improvement, maybe its too slight too notice. Is this probe getting old and time to replace? Also, this probe has the black wires. What the hell is the difference (other than the inside resistance , maybe? or length?) between red and black wire probes? How silly to have 2 probes that I swear look totally alike only that they have different colored wires. Also, if I buy a new probe, I should only buy a Harman part right? I see a lot of aftermarket parts now. I have no clue if these aftermarkets are just as good as Harman parts or if an aftermarket ESP probe even exists.


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## smwilliamson (Jan 9, 2013)

ESP monitors the exhaust temp. Sounds like you need a new room thermistor or....you need to place the thermistor up higher than the stove (get it off the floor) as you may be monitoring the cold air return. Add some insulation in yer house too perhaps. There are not too many aftermarket sensors our there for Harman


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## smwilliamson (Jan 9, 2013)

red is digital, black is analog and they are different diameters...red it thicker


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## rickwai (Jan 9, 2013)

Replace room sensor probe. They r not very expensive.


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## Lousyweather (Jan 9, 2013)

maybe the RSP is bad, though Im not convinced. Take a temperature reading WHERE THE END OF THE PROBE IS, not  just a general room temp. Someone with a DDM can also plug in and see what the probe is actually reading and act from there. Unfortunately a new probe is almost certainly less than a service call.

Red Vs Black probe? Different animal.....the only production Harman still utilizing the black wire probe are the P38's....all the rest now come off the line as red. And now that the board has chabged on the 38's they may be red too. The probes are the same diameter as well, so, physically interchangeable. If you do change colors, make sure you also change dipswitch settings!


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## kinsmanstoves (Jan 9, 2013)

ESP either work or they do not.  If the ESP is bad you will get a 3 flash on the status light.

Eric


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## CelciusMaximus (Jan 9, 2013)

i had some crazy issues with an accentra insert(2006 vintage) about a year ago.can't remember what the issues were ,thought it was the board or the esp.
decided to change the esp first (process of elimination).sure enough that was the problem did not have blinking lights or loose connections.
sometimes things are intermittent


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## CelciusMaximus (Jan 9, 2013)

https://www.hearth.com/talk/posts/1085034/
here is the post


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## Val (Jan 9, 2013)

Val said:


> I wrote about this before. My 2006 Accentra is reading room temperature "funny" on room temp. mode. It seems about 10 degrees off. I mean I have to set it over 80 degrees to get the room to 72. It never used to do this. Have run about 15 tons of pellets probably since I owned the stove. (I do clean the vent pipe and stove insides, too) Well, I finally took the esp probe out of the ehaust and cleaned it with a green scrubbie pad. It only had a very very thin layer of carbon on it and some ash. Well the stove still seems to do the same thing. If there is any improvement, maybe its too slight too notice. Is this probe getting old and time to replace? Also, this probe has the black wires. What the hell is the difference (other than the inside resistance , maybe? or length?) between red and black wire probes? How silly to have 2 probes that I swear look totally alike only that they have different colored wires. Also, if I buy a new probe, I should only buy a Harman part right? I see a lot of aftermarket parts now. I have no clue if these aftermarkets are just as good as Harman parts or if an aftermarket ESP probe even exists.


The other thing that is happening is if I put the stove on stove temperature mode, the pellets will light up, burn for a while, but then burn down, shove will shut off and I will get a 5 blink status. Now, I am running some older pellets which maybe didnt ignite so well, but what I will do is scoop them out of the hopper and intermix what is left with fresh pellets. The thing is is that these older pellets still burn, and I will anticipate that I just might get the problem with the new pellets as well. My igniter area is clean. I get the 5 blink status after the stove has been up and running for less than an hour on stove temp mode, then the stove shuts down by itself. I can always change the room temp probe...but when troubleshooting is it always better to try to replace one part at a time and then see the result. Eric said if it is the esp probe it is 3 blinks and either good or bad, but I see a lot of posts on esp replacement. do some of these have esp repacements on 5 blink status as well. I notice that my Accentra has developed these behavior issues very slowly, perhaps over the last 2 years. Not really going bad all at once but i would rather correct things before I end up with unreliable stove behavior. None the less, room temperature off readings had still been a gradual problem for a while.


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## Delta-T (Jan 9, 2013)

sometimes if the ESP probe is coated in ash you'll get the 5 blinks cuz it wont see the actual temp of the exhaust in the timeframe it requires to know that it is running. Another not uncommon symptom of a bad ESP is that the stove will not completely shut down in the "off" position but will continue on its idle burn indefinitely. Always eliminate the obvious things by giving the stove a proper cleaning before assuming you gots bad parts. Stoves sometimes need a good talking to as well. They can get very big headed.


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## Val (Jan 10, 2013)

Delta-T said:


> sometimes if the ESP probe is coated in ash you'll get the 5 blinks cuz it wont see the actual temp of the exhaust in the timeframe it requires to know that it is running. Another not uncommon symptom of a bad ESP is that the stove will not completely shut down in the "off" position but will continue on its idle burn indefinitely. Always eliminate the obvious things by giving the stove a proper cleaning before assuming you gots bad parts. Stoves sometimes need a good talking to as well. They can get very big headed.


one thing i was curious about is what the esp is made of. is it like the oxygen sensor in the car exhaust (before the catylitic conveter) so that it is made of a material inside that breaks down over time? Did you ever saw your old esp probe in half to see the inside? I looked up info on the temperature sensing bulb and found out that those devices are pretty common and how they are made. But what is inside of the esp probe that makes it work?


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## Delta-T (Jan 10, 2013)

its variable capacitance. most of the thermisters I know of work on resistence, so the Harman Esp I guess is a bit different. Inside is a couple wires, beyond that I dunno. Electronics is not one of my specialities. I have the tools to test the probe, but I don't claim to truely understand how it works.


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## daveq (Nov 2, 2014)

Delta-T said:


> its variable capacitance. most of the thermisters I know of work on resistence, so the Harman Esp I guess is a bit different. Inside is a couple wires, beyond that I dunno. Electronics is not one of my specialities. I have the tools to test the probe, but I don't claim to truely understand how it works.


Hi, my accentra insert has status light blinking 3 times and will not reset I have replaced esp with new one of same color and still same 3 blinks. Could you tell me how to test the esp or if i could bypass probe. I was thinking if it was just a thermal coupler i could install old one and just jumper wires together. Stove will not light unless manually use fluid and runs very low as exhaust fan runs on high and feed motor runs low but will not shut down on its own in off position  I have to unplug stove...  Thanks Dave Q


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## sderaps (Nov 17, 2014)

daveq said:


> Hi, my accentra insert has status light blinking 3 times and will not reset I have replaced esp with new one of same color and still same 3 blinks. Could you tell me how to test the esp or if i could bypass probe. I was thinking if it was just a thermal coupler i could install old one and just jumper wires together. Stove will not light unless manually use fluid and runs very low as exhaust fan runs on high and feed motor runs low but will not shut down on its own in off position  I have to unplug stove...  Thanks Dave Q




Did you ever fix the problem, I have the same problem with my pellet stove right now.. Help


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## ajbass (Nov 12, 2016)

Is there a resistance test for the ESP probe.


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## nlstockstill (Oct 29, 2019)

Anybody have a solution??  I know it’s an old thread


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## Ssyko (Oct 29, 2019)

yes with an electrical multimeter you can test all the harman temp probes. red ones are between 1,000 to 1,100 ohms of resistance depending on what your room temp is (remember if the stove has been off for a while the probe may be much colder from the cold air outside coming through the OAK. All other ESP probes that are NOT red should read around 650,000 to 550,000 ohms resistance. After taking a good initial read you can breath on them or use any heat source and the resistance should lower as the probe heats up except the red which should rise, hope this helps.


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## nlstockstill (Oct 29, 2019)

Wow thanks for the quick response! Now I can check that....in another week when I get home.

I’m getting the 3 blink, ESP Fault. Stove will power on and feed pellets but never ignite. Thinking maybe the igniter is shot I thought I’ll just fire it up manually. Unplug, and then plug back in, fill the hopper with pellets, put some fire starting gel on it, turn the stove on everything seems to be taking off like it should. Combustion blower, distribution blower, exhaust fan, all working. And shortly I can see the igniter is starting to work. ( possible I never put it in “manual ignite”). 
now I’m thinking, great, it’s all working as it should. I hear a click and the igniter shuts down, and the combustion blower stops. Fire slowly fizzles out. I walk away thinking the blower motor will shut down shortly. Forget about it for the day and come back a good 8 hours later and it’s still feeding pellets. Overfilled the burn pot and I’m sure it is giving the auger motor a workout at this point.
So after all this, anybody have any suggestions? I hate to buy a $300 control board just to throw parts at it. I am fairly remote so I don’t know how steep a service call is going to be
Thanks


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