ReplyCheck for leaky dryer vent, open laundry detergent containers, open paint cans, litter boxes, or anything else of that nature.
Then check for adequate combustion air supply.
Regular Guest
Had a no heat call today on a system I was at a month ago for regular maintenance and found today that the flame sensor was dirty I was reading .2 ua so I cleaned the flame sensor check my ua and it was back up to 2.8 after cleaning my problem with that though was that I cleaned the flame sensor on the maintenance call and was reading 2.8 ua after cleaning it then as well I got to looking at the work history on this call and saw that our company (i have only worked with this company for the past 7 months) has been out there 3-4 times a year cleaning this flame sensor and has even been replaced twice any suggestions as to why this may be getting dirty so quick so I can get this problem resolved and keep a good loyal customer from getting angry with the company
Professional Member*
Check for leaky dryer vent, open laundry detergent containers, open paint cans, litter boxes, or anything else of that nature.
Then check for adequate combustion air supply.
Professional Member*
Something in the air is contaminating it. Find the source and remove it or find a different source of combustion air. The next problem you'll probably be seeing is a HE failure if you don't.
Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.
Professional Member
If it's sealed combustion, make sure the intake is pulling in clean air. No recirculation, no other exhausts nearby etc. If it draws combustion air from the room, as mentioned by others, check for contaminants and remove.
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Regular Guest
Thanks everyone for the replies this is a residential furnace 80 percent however it is installed in a dry clean drop off building meaning clothes are dropped off at this building the clothes are then removed from the building washed and the reaturned so the litter box for a cat is out, the dryer vent is out because there is no dryer They don't do any cleaning at all in this building laundry deteregent is out and it's mounted in a suspended ceiling with plenty of combustion air. Kinda like wtf is going on because it is a very clean building
Member
If you cleaned it with sandpaper it might be corroding.
Regular Guest
Cleaned it with a steel brush
Member
I think steel wool is the way to go. Might have chinese drywall or oil refinery near by, just throwing darts.
Professional Member*
Have the burners been cleaned? I've seen crud in the burners come out and coat the sensor.
Professional Member*
So dirty clothes come in to the building?
Where do you think dryer lint comes from?
What does the sensor look like when you remove it?
Ash coated? Discoloured? Burnt? Or clean?
Regular Guest
Looks spotless
Professional Member*
Well if cleaning it increases the ma, it's not spotless.......... that is unless.......... the connection is the culprit. That'd be a new one on me.Originally Posted by tkhvacguy
Contamination of the sensor can be in many forms. Something is increasing the resistance of it.
Did you say it was mounted above a suspended ceiling? Is the ceiling the fiberglass ceiling tile type with the metal grid work? Might be microscopic fiberglass particles being melted onto the sensor. Glass is a good insulator and would be hard to see.
Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.
Regular Guest
That's a good point I do believe its a fiberglass tile not only that bit it's got the pink rolls of insulation right above it I could very well be getting insulation on it ill have to check it out but if that's the case the only way to correct it is to get its combustion air from outside and we would probably have to put a 90 percenter in instead well see what comes of it thanks for the help guys
Professional Member
What is the gas pressure set at? Cleaning a flame sensor with anything abrasive is a bad idea. I use a shop rag or the flap of my cargo pocket. It doesn't take much to remove the buildup...unless someone cleaned it once with a wire brush or sand paper and now it is corroding. I would replace the flame sensor and start fresh.
Regular Guest
Gas pressure is 3.48 " wc
Regular Guest
Try reversing hi voltage to the unit , a class i attended claims polarity will cause flame sensor fault .
Professional Member
The flame is conductive and the circuit is between the flame rod and the burner. So be sure to clean the metal parts of the burner near the flame rod so you get good current. You should also put a meter in series with the flame rd and see what your getting.
Professional Member*
could be highly underfired or lack of post purge. this is causing the acids in the flue gas to attack the flame rod at off cycle.
Professional Member*
I have a 2 stage Ruud furnace that once a month amber light blink clean it and I comes back in a month later replaced sensor now gonna change the board this is direct vent to outside 12 ft above the ground
Professional Member
Do you mind if I ask exactly what brand and model of furnace this is. I ask, because over the years, at times manufacturers have had service bulletins, and changed components for exactly the reasons you have described, which has included flame sensor changes, relocation changes, and ignition module/circuit board changes. Myself or other members here might be able to help you if we have the exact unit you are referring to. If not, have you called the manufacturer tech support to see if they have made changes.
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