DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Natural Gas Furnace - no heat


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Old 12-20-2016, 07:49 PM  
madrussian
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Originally Posted by nealtw View Post
You didn't answer all of Buffalo's question.
Sorry - yeah replaced all filters. Didnt climb on the roof (not a ladder guy). However given the information that when induction fan comes on, the pressure switch closes, I think it is safe to assume there is no blockage on top of the roof.


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Old 12-20-2016, 07:54 PM  
madrussian
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Originally Posted by kok328 View Post
Your trying to determine voltage TO the inginiter so test the leads that connect to the igniter, not the leads on the igniter.
and of course you know not to touch the igniter with your fingers.
Inspect the igniter for hot spots and hairline cracks but, i think you already ohmed it out at 50
Sorry yeah that is what i meant - voltage to the igniter. I checked this and I now think the power supply is suspect. got 120 VAC going to the PS, but nothing coming out of the 24 V.


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Old 12-20-2016, 08:25 PM  
kok328
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If your transformer was bad you would not have gotten that far in the ignition sequence.
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Old 12-21-2016, 05:05 PM  
DFBonnett
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FWIW, some years back I had the same problem, but on a less complicated furnace. The gas valve had failed and did not open. A new gas valve was the fix.
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Old 12-22-2016, 03:29 AM  
WyrTwister
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Can you visually verify if the HSI comes on or not ?

Can you post a photo of the control wiring diagram ?

Pretty sure the HSI operates on 120 VAC .

God bless
Wyr
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Old 12-22-2016, 06:24 AM  
madrussian
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Originally Posted by WyrTwister View Post
Can you visually verify if the HSI comes on or not ?

Can you post a photo of the control wiring diagram ?

Pretty sure the HSI operates on 120 VAC .

God bless
Wyr
I assume the HSI should come on after the induction fan comes on:

Yes after looking at the schematic in the manual, the HSI is on the high voltage (120v) circuit.

I need to look at this a little closer. Should be able to check this voltage today - got a multimeter that works.

Last edited by madrussian; 12-22-2016 at 06:37 AM.
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Old 12-22-2016, 07:01 AM  
kok328
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Your jumping all over.
Use a systematic approach to troubleshooting.
Start with line power and then check control power.
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Old 12-22-2016, 08:27 AM  
madrussian
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Quote:
Originally Posted by kok328 View Post
Your jumping all over.
Use a systematic approach to troubleshooting.
Start with line power and then check control power.
Agreed.

Part of what I do not know is order of operation of a furnace. No Idea. If anyone can provide this, would be a great help!

Part of my initial problem was the multi-meter I have was suspect, so some of the first troubleshooting was not accurate.

This is what I know/done:
1. First noticed an issue. Induction fan would run, nothing else.
2. The LED was flashing 3x. According to manual this is a vacuum switch/induction problem.
3. Replaced vacuum switch, no change.
4. Checked resistance of both switches. Both are OK. When induction fan OFF = infinite ohms. When induction fan ON = 0 ohms.
5. Checked resistance of HSI = 53.9 ohms.
6. Double checked all incoming voltages (with new multi-meter). Got 120 VAC at main on/off switch, junction box going into furnace and at the transformer.
7. Checked voltage going into the HSI. Getting ~1 VAC. But again I do not know the order of operation. So I do not know if this should be ON or OFF yet.
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Old 12-22-2016, 09:36 AM  
madrussian
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Checked voltage coming off the control board to HSI - nothing there. (with induction fan ON)

Also checked primary limit and aux limit switched - both are closed (indicated normally closed on schematic).

When I was checking voltage on the control board a few of the relays were turning on/off, so possibly the control board has failed?
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Old 12-22-2016, 10:19 AM  
madrussian
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With no other place to go I found a few pretty cool tools for the control board:
1. troubleshooting manual: https://www.manualslib.com/manual/55...?page=3#manual
2. Schematic for control board: https://arnoldservice.com/wp-content...structions.pdf

Using the troubleshooting flow chart, it has guided me back to the 120v/24v transformer. Got voltage going in, nothing coming out.


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