Hi All, I got a nice older small compact rheem "conquest 80" 50k hot air furnace that was set up for horizontal flow. everything seems OK, green "ok" light comes on on the board. Model GKDA50-E3N
but when it fires up, the blue flames only last 5-10 seconds and the board commands a shut down (I hear the click). The main blower doesnt even start to run because it doesnt even get warm enough.
According to the diagnostic flow chart on the unit if burner lights but does not stay on,, it says to
check the power polarity. (it only ran when hooked up one way, so not that)
check the ground continuity (the green wire is grounded at the outlet)
check the insulation on ignitor leads (no idea but looks ok)
if checks are ok, replace the IIBC (is that the control board?)
this unit looks in good shape especially the heat exchanger so I'd like to fix it. any ideas?
Are those three round silver sensors (with the red wires) they connect in series with a hot air temp sensor in the plenum. I think they are my flame detectors but why three? (There is NO traditional flame sensor in the fire path, other than the ignitor, which I guess could also be the flame sensor).
thanks!
Last edited by diyer5; 12-13-21 at 12:37 PM.
Reason: add model
I can't find any technical manuals on that furnace.... only a several page spec sheet on the series.
There should be an ID tag inside on the side wall near the burner. Post that complete model number.
The sensors that face the burner would be the flame rollout switches. They are in series and any one that trips will set a rollout code. The rollout switches have a red reset button on the back. If they trip the red button must be manually pushed in. A flame rollout problem must be addressed by a pro.
There are other limit switches on a second loop. They would be general high heat limit switches.
Any fault should set a blinking fault code that will point to the problem.
I believe that furnace uses an intermittent ignition system. That would be a spark electrode that doubles as the flame sensor. That may need to be cleaned. I see what looks like the two wires from a standard hot surface igniter but I don't see the igniter.
Hi Pete, thanks! you brought me some luck... (and knowledge)
When I went outside to run it and look for a blinking code as u mentioned, now it stays on. No idea what changed. BUT I do have a few more questions since this may now be turned into a portable heat source for my shop.
You pointed me to read and watch video on flame rollout switches! Now I know what they are. That loop has three flame rollout switches and a hi limit, all in series on the same 2 wires.
The igniter is the kind that glows red. It has 2 wires to it.
So, if the 3 rollouts just protect from flame rollout or rollback, and there is no flame detector, is that igniter possibly also the flame detector?
Does the picture look like a healthy flame?
I blocked the exhaust with my hand and it shut down instantly, there seems to be a pressure switch on the inducer blower that must do that, and its working.
There might not be a flame sensor switch (as a separate part) but there is a sensor. The ignitor stays energized continuously so if the flame goes out for any reason it is immediately re-lit. If the ignitor goes bad or dies then the gas valve automatically closes. Here is a photo of a flame sensor and they have one wire (an ignitor usually has two wires):
From the photo your flames look good. I look down inside the flame tube when the air handler fan is running. Look for any sign that the flame is being blown around, sucked to the side anywhere down inside the tubes which can mean the heat exchanger is rusted or cracked. Also watch the flames after ignition. With the air handler off the flames will nicely go down the tubes. If you see some blowback or puffing when the air handler turns on that also indicates a heat exchanger leak. If you any see sign of that have it inspected by a pro and do not use the furnace as carbon monoxide and be blown into the home.
Here is a video that shows a furnace with a cracked heat exchanger.
Last edited by Pilot Dane; 12-14-21 at 10:57 AM.
Reason: clarified flame sensor comments
Thanks guys. I ran it for 15 mins no issues. The H/E looks good visually to me but Im not a furnace tech. Blocked the hot air outlet briefly and no rollout or flame change.
One thing that bugs me a little is that occasionally the flame starts inside one of the trumpets. The one with the ignitor. It eventually gets sucked thu to normal. No rollback just blue inside the trumpet about an inch from the jet.
Also, the flames are blue where they start with some yellow in the middle and at the end.
This will be a portable heater on a cart for my shop or wherever I need warm air...
My Rheem propane unit stopped igniting the gas during start-up due to the HSI not heating up during the HSI energize cycle. System would go through the following cycles and repeat 3 times before locking out the system.
(1) 30 second pre-purge cycle with draft inducer running
(2) 34 second HSI energize cycle, draft inducer still running
(3) 9 second propane release, draft inducer still running
Original HSI was a Norton 201N part number 62-22868-02 that measured OL for resistance. I first replaced it with a Supco IG418 which I later found out cross-references to a Norton 271N HSI and not the 201N. The Supco IG418 measured 75 ohms resistance and the furnace would then progress through the three cycles above followed by shutdown of draft inducer and startup of the circulating blower as if the propane had been ignited even though the HSI still did not heat up and no flame was produced,
I got the following measurements from hot & neutral wires at the HSI plug to ground when not connected and when connected...
[img]https://cimg9.ibsrv.net/gimg/www.doityourselft.com-vbulletin/752x250/supco_ig418_cbac21e9fabf8d74310a6e6f294abd97c30aaa2a.jpg[/img]
I then got a Duralight HSI Part Number 62-22868-93 which is supposed to be a direct replacement for my original HSI. The resistance on this HSI measures 118.9 ohms. Same thing is happening with this HSI...furnace goes through the three cycles listed above followed by shutdown of draft inducer and startup of the circulating air blower as if the propane has been ignited, but the HSI never heats up and the propane does not ignite.
The VAC measurements from hot & neutral to ground at the HSI plug when the Duralight HSI is connected are shown below. Also shown below are the amps going through the wiring to the HSI with the Duralight plug which is only 0.19 amps during the HSI energize cycle (same as the pre-purge cycle).
[img]https://cimg8.ibsrv.net/gimg/www.doityourselft.com-vbulletin/754x220/duralight_hsi_d3bf83d80d2f510727c78b9eb1fbee10f8ff3b09.jpg[/img]
I have verified that the air validation switch is closing during the pre-purge cycle and remains closed during the HSI energize cycle and propane release cycle. I also have two flame rollover switches mounted above and below my three firing tubes and I have verified they are closed during all three cycles.
The circulating blower starts with either HSI connected without any flame regardless of whether or not the flame sensor is connected to the PC board.
The Power and OK lights remain solid green throughout the cycles listed above with no blinking to indicate any type of error.
The board has a burn mark between where the HSI and draft inducer power plugs into the board and a relay. I don't know what the relay controls, but I am hearing relay clicks from somewhere on the board before/after each cycle listed above. See picture of burn mark below.
(1) Any idea what the cause would be for the HSI to not to heat up? I assume 0.19 amps is not sufficient.
(2) Any idea why the VAC readings are different for the two HSIs during the 30 second pre-purge cycle?
[img]https://cimg3.ibsrv.net/gimg/www.doityourselft.com-vbulletin/756x528/board_burn_004b542996f8f3db0aadd9e1de3de9807feab021.jpg[/img]
Hi experts,
My home is equipped with Trane XR80 TUD040C924K furnace. Several days ago it started to work inproperly. After several tries I got the pattern:
1. The red light shows 3 blinks. This is the general situation.
2. If I turn the power off, then turn it on, it started to work normally and blows out hot air
3. But it can't restart once it's stoped due to the temperature set.
4. When the temperature is met, it stops and the light flashes slowly (indicating no heat needed)
5. After a while the light flashes fast, indicating it's trying to start the ignitor
6. Then the fast flash turns to 3 flashes indicating an error on air presure switch.
7. But when I turn the power off, and after a while turn it on, it can start the ignitor as usual.
8. The filter is not dirty.
9. I tried to blow air into the tube connecting to the air pressure switch according to some videos on the website.
10. The air pressure switch is honeywell C341750P03 or MP2168, 0511D3/B, IS20137-3312. I don't know which one identifies it.
I bought a ohmmeter yesterday but it's still on the way of shipping. However I don't think it's because the air pressure switch is bad because it can work normally everytime I disconnect and reconnect the power. Before calling some technicians to my home, could someone help me to do more by myself?
Please excuse my poor English and help me out. Thank you!
12-13-21, 11:31 AM
