My WeatherMaker 8000 seems to not be heating up properly. When I switch on power to it and let it fire up, the inducer switches on and it seems like air is flowing. But I never see the HSI glow or the burners switch on.
When I examine the status light, it appears that it is showing a code of 31. Three short lights followed by one long. I've attached a video of the start up here:

https://www.dropbox.com/s/9hpezouv5hcy5oh/IMG_1714.MOV

I'm not very familiar with HVACs, but I'm wondering what steps I can take to diagnose this issue? Is it something I can fix myself or do I need a professional?

The HSI is one of the easiest parts to replace in this furnace. Take it out (carefully, as it is ceramic and fragile) and check the resistance between the two contacts. I'm not sure of the "good" value, but if the resistance is infinite, the HSI is burned out. You may or may not be able to see a small crack in the black ceramic.

Go to a good appliance parts store and get an equivalent HSI. Should be $25 or so. Put it in and enjoy the heat!

Good luck,
WallyH

Just because the HSI doesn't light doesn't mean it is bad. Could be a non reset safety switch, could be a high temp overload. Don't just replace parts . Read the blink code, usually on the inside of the air handler door or on the control board. If it is a HSI, most are very easy to replace, $25-40

Very true! You hope it is the HSI, as it is inexpensive and simple to replace. However, test it as I indicated before buying a new one. Since you are getting an error code, you should focus on that area. As ma0641 says, it could be a switch, etc. causing the problem.

Good luck,
WallyH

Before replacing parts, TEST. If you have a voltmeter & know how to use it, during the whole ignition process check for 120 volts to the ignitor. If you get 120 volts & the ignitor does not glow, replace the ignitor. If you do not get the 120, most likely the problem is a venting issue.

Measure my old HSI. Resistance was infinite. SO I bought a brand new one and installed it just as the instructions suggested. Still though when I switch on the heater, I don't see it glow.The inducer comes, I can hear air blowing. However if I look around the house I don't feel any air out of the vents. Nor do I see anything happening with the burners.What should I check next? I've never fixed one of these before. So I'm not sure what I'm looking for always. And the manual I found for my unit does not match up very well to the actual control board that I'm working with at the moment.Thanks.

Hi easy, do you have the 120 volts at the ignitor? Did you have 120 volts at the old one?

You may want to run the built-in self-test. The procedure below may not match exactly your board, but it should be close. I agree with the other posters that you should check for 120 volts at the HSI connector, and you can do that by disconnecting the HSI and plugging your meter into the plug during the test. When you get to the step that powers the ignitor, you should see the meter jump to 120 volts.

Component test—The furnace control board allows all components, except gas valve, to be run for a short period.
This feature helps diagnose a system problem in case of a component failure. To initiate component test procedure, short
(jumper) the TEST 3/16-in. quick connect terminal on control (behind the Y/Y2 terminal) and the COM-24V terminal on
furnace thermostat connection block for approximately 2 sec.

NOTE: Component test feature will not operate if any thermostat signal is present at control board.
I disconnect the thermostat wire from the R terminal right there on the main board.

Component test sequence is as follows.
a. Momentarily jumper TEST and COM-24V terminals until LED goes off.
b. LED will display previous status code 4 times.
c. Inducer motor starts and continues to run for entire component test.
d. Hot surface igniter is energized for 15 sec, then deenergized.
e. Blower motor operates on FAN speed for 10 sec, then stops.
f. Blower motor operates on HEAT speed for 10 sec, then stops.
g. Blower motor operates on COOL speed for 10 sec, then stops
h. Inducer motor stops

Don't forget to hook the thermostat wire back up!
45604

WallyH

P.S. You had mentioned earlier that you had a code 31. For my furnace, that indicates these possible problems (note HSI is not in here!):

PRESSURE, DRAFT SAFEGUARD, AUX-LIMIT SWITCH (when used*) OR BLOCKED VENT SWITCH (when used) DID NOT CLOSE OR REOPENED
(DOWNFLOW ONLY*) If open longer than five minutes, inducer shuts off for 15 minutes before retry.
Check for: - Proper vent sizing
- Low inducer voltage (115VAC) - Defective inducer motor
- Defective Blower motor or capacitor - Restricted vent
- Defective pressure switch - Excessive wind
- Inadequate combustion air supply
- Disconnected or obstructed pressure tubing
If it opens after trial for ignition period, blower will come on for 90 second recycle delay.

All right everyone. Thanks so much for the comments. Here is my progress so far:

1) I've confirmed that I am getting 120V at the ignitor
2) I ran the self test. The self test seemed to run all tests successfully. The inducer came on, the HSI lit up, and the 3 blower tests occurred. I've added a video just in case I missed something:

https://www.dropbox.com/s/vi88lmjlvivtmzf/hvac_self_test.MOV

So in terms of code 31. I think that the below possibilities are not the problem:

- Low inducer voltage (115VAC) - Defective inducer motor
- Defective Blower motor or capacitor - Restricted vent
- Inadequate combustion air supply

What it seems like it could be is one of these:
- Defective pressure switch - Excessive wind
- Disconnected or obstructed pressure tubing

I figured that I should check my gas vent and see if it is obstructed. My gas vent goes from my condo up into the roof of the building. I went an check it and found this:

https://www.dropbox.com/s/20wjts92pebyece/hvac_vent.JPG

It looks like my vent cover is gone! So I turned my HVAC back on and stood up there to see if any gas was coming out. Sure enough there was gas coming out. I know I need to fix this and cover that, but I don't think its getting blocked.

What steps should I take now? Could it be the pressure switch? What other things should I test? Thanks so much for all the help.

First off, well done on your diagnostics work! You are rapidly reaching the limit of my ability to offer additional help. Hopefully some of the experts in this area can chime in.

I think testing the pressure switch is a great next step. You need to know if it is the switch itself, or if the switch is indicating an actual safety problem.
Grayfurnaceman on YouTube has a good video that might help you here (https://www.youtube.com/watch?v=qQ2b-DZ82Bs). If you're like 99.999% of the population, you won't have a manometer (neither do I), but if it were me, I would pull the tube from the switch and see with your finger if there is any vacuum when you are running the self-test. It's not exact, but might be a quick go/no-go indication.

Best of luck,
WallyH

Easy,
Once you check the switch with the ohmmeter as shown in the video, if you find the switch is not closing & the pressure spec is on the switch, you can get an approximate idea of what the venter is doing by using the homemade manometer shown here:
RV U Tube Manometer (http://www.rverscorner.com/manometer.html)
You will need a barbed adaptor to adaptor to go from the size of your tubing to the 1/2" used on the manometer. You can use tubing smaller than the 1/2" if you so desire.

Ugh, I figured it out. There is a button on the pressure switch. When I pressed it everything started working. I don't remember seeing anything about that in the manual. But it was very easy to fix :-\. Thanks for all the help though, I certainly learned a lot with this exercise.

Thanks for the update, this will help someone later I'm sure.

I don't recall as to ever having seen any kind of button on a pressure switch. Can/would you post a photo of it?

Okay. Here is the picture. You can see between the two orange leads a little tab there. By simply pushing that knob I was able to fix the problem.

45648

Sorry easy, I couldn't see the attachment.

Let me try with dropbox. Can you see this link:

https://www.dropbox.com/s/x549pu6e33azuh7/PressureSwitchKnob.jpg

That's not a pressure switch. It is a thermal limit & will trip if it gets too hot. The pressure switch is the device below the limit.

Hi easy, that looks more like a limit switch to me, does it have a tube running to it?

sorry Grady, I type slow.

Ah yeah, knew I said the wrong thing. It's the limit switch. Easy fix :-\.

Limits usually don't go bad. It's not unheard of but usually they are just doing their job. Usually when limits trip, it is due to an air flow problem. That being said, limits are cheap & easy to replace. If the problem persists, then look for the cause.