Original message
| pwned
 |  "gas valve is teh click, clickety click. :("
, posted Sun 13 Jan 23:28:  
I've been having problems with the furnace section of my package unit. In October, I changed the draft inducer after the old one seized up and now, it's been having new issues.
It does not consistently fire up properly and when it fails, I can hear the gas valve repeatedly clicking every two seconds or so and it would not fire up unless I stop calling for heat, then call for it again.
The gas valve and the module are both Honeywell. It is spark ignition and the electrode serves the purpose of both spark plug and flame sensor. I was able to verify that shorting the ignitor after ignition would kill the flame.
What I have done so far: I have re-made the ground contact in center-left part in red circle by removing it, sanding down both surface and treating them with Caig DeoxIT, then I verified the integrity of the grounding by taking resistance measurement between "A" where the ground lead attaches to module and at the base of flame sensor mount.
When I short "C" to ground in operation, the valve shuts off, verifying that ignition electrode is indeed used as a flame sensor as well, however I have not taken the megaohm reading from electrode connection to ground to test the integrity of insulation(is this a likely problem?)
During test, the valve buzzed in middle of operation and the flame died out for a split second, but I was unable to reproduce it again during test operation.
I'd like to figure out whether the drop is caused by something(centrifugal switch in inducer motor, the ROC/LC module, flame sensing) telling the module to shut off the valve, or the valve itself malfunctioning and I plan on probing the voltage at gas valve terminals when the malfunction occurs, but I'm not able to get it to reproduce the malfunction while I'm at the furnace and the furnace functions properly more often now, but it still acts up from time to time.
What do I do now, diagnostic wise? I prefer to fully diagnose it before changing parts.
Schematic:
[this message was edited by pwned on Sun 13 Jan 23:31] |
| Replies:
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| acefurnacefxr
| "Re(1):gas valve is teh click, clickety click." , posted Mon 14 Jan 06:59
Since there is no true and seprate flame sensor, its not possible to check how strong the flame signal is. I belive that furnace is over 20 years old isint it? I would say 86 the furnace for one with a true sensor set up.Or switch it over to a true 3 wire valve set up. All you need is a valve, control and new pilot head with sensor.The wiring is simple to do, and you will have far less troubles in the long run.
HVAC REPAIR IS NOT A DIY WEEKEND PRODJECT
I have been performing HVAC repairs for 23 years
http://www.hillaryclinton.com
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| | 341
| "Re(2):gas valve is teh click, clickety click." , posted Mon 14 Jan 19:01
Alot of those older modules will give you a flame signal if you measure in series with the BRNR-GRND wire and module. Just make sure the secondary of the transformer is ungrounded while you test.
Sounds like a flaky module. I would clean the electrode / pilot and change the module.
www.hvactechgroup.com
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| | pwned
| "Re(3):gas valve is teh click, clickety click." , posted Fri 18 Jan 03:26
Everytime I go up on the roof, the damn thing works.
Flame current ~4.0ľA, looks ok.
When there is a problem, I hear clicking repeatedly through the return air ducting.
Connected ammeter across W & R on thermostat connection.
It would draw about 0.2A, draft inducer runs, it draws 0.5A, then when running about 0.75A. When there is a repeated clicking, it would cycle back and forth between 0.5 and 0.75A.
So, the valve is either sticking intermittently, therefore not being able to ignite, and cause it to repeat all over.
Or, something independent of valve is the module to order the valve to not fully turn on.
Unless I can get it to reproduce the problem while I have the cover open, I can never figure out what's happening. What do I do now short of replacing both the module and valve?
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| | marchvac
| "Re(4):gas valve is teh click, clickety click." , posted Fri 18 Jan 20:18
I have worked on a few of those units and it is probably the ignition mod. Check the heat exchanger before you throw any money at the unit. Do you know what the microamps should be for that mod?
Be careful sometimes you don't get a second chance
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| | pwned
| "Re(5):gas valve is teh click, clickety click." , posted Wed 6 Feb 01:15:
quote:
I have worked on a few of those units and it is probably the ignition mod. Check the heat exchanger before you throw any money at the unit. Do you know what the microamps should be for that mod?
...
The new inducer motor cost $60 and I spent another $65 on a new S8610U 3009 on eBay. If that gets me through even this season, it's not a bad investment.
I located an internal block diagram on Honeywell page and now that I've seen it, I agree, it's the module. Until now, I thought the module is solid state. Boy was I wrong. It's a relay logic, with THREE relays in SPDT setup.
(LOL 68-0085, Honeywell, December 1989)
I also looked at the S8610U schematic. The block diagram is basically the same. The only difference is the schematic is CAD drawn.
I'm thinking the contacts on 2K2 and 1K2 are wearing out and needing multiple tries before making proper closure, thus the repeating of first sequence, but inability to get into second.
After I replace the module, I will tear it apart and inspect the relays and report back the result. Had I know the internal workings of the module was electromechanical, I would have suspected sooner.
[this message was edited by pwned on Wed 6 Feb 01:46] |
| | marchvac
| "Re(6):gas valve is teh click, clickety click." , posted Wed 6 Feb 20:29
Hopefully that module is good. Normally I pay about $150 new. Hope it works out. Let us know what happens.
Be careful sometimes you don't get a second chance
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| | pwned
| "Re(2):gas valve is teh click, clickety click." , posted Mon 14 Jan 17:14
A new package unit would be nice, but since it's gotta be raised and lowered with a crane, it's rather laborious.
I've gotten bids in the range of $4,500 to $5,000 and we don't plan on staying in this home for all that long, so this is not the kind of investment I'd like to make.
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| | northernfitter
| "Re(3):gas valve is teh click, clickety click." , posted Tue 15 Jan 21:07
if its spark ignition pilot it could be as simple as changing the pilot. I kind of wonder though since you just changed the ventor does this unit have a pressure switch? If so it could very well be a chattering pressure switch. I am not familiar with that unit though.
12years as a service tech in Ottawa and the valley. Just left Direct Energy to start my own company. Go to www.reliableheating.ca or email me at adrian@reliableheating.ca
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| | pwned
| "Re(4):gas valve is teh click, clickety click." , posted Wed 16 Jan 21:14:
" if its spark ignition pilot it could be as simple as changing the pilot. I kind of wonder though since you just changed the ventor does this unit have a pressure switch? If so it could very well be a chattering pressure switch. I am not familiar with that unit though. "
No, this unit does not use a pressure switch. You see those orange wires coming out from the oddball looking draft inducer (the one with date written on it)? Those wires goes to the centrifigural switch inside the inducer assembly. (it is marked as CC on the schem)
Another thought:
What's the likelihood that aging dirty burner is causing the flame to have distorted pattern and getting off track from the sensor, thus triggering detection failure?
[this message was edited by pwned on Wed 16 Jan 21:21] |
| | northernfitter
| "Re(5):gas valve is teh click, clickety click." , posted Sat 19 Jan 12:11
I have seen those switches chatter on the Colemans before either way I wouldnt jump to burners or pilot without making sure there is a strong 24v to the module when it is chattering.
12years as a service tech in Ottawa and the valley. Just left Direct Energy to start my own company. Go to www.reliableheating.ca or email me at adrian@reliableheating.ca
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| | pwned
| "Re(6):gas valve is teh click, clickety click." , posted Sat 2 Feb 01:32
The draft inducer is a brand new. Full control current flows through the thermostat in this circuit, so I monitored current going between R & W at the thermostat connection and I didn't see a current fluctuation that would indicate chattering switch.
I think it's the module. I finally got to the furnace when it was acting up.
Thermostat calls for heat. It activates a relay, then sends 208v to draft inducer activating the centrifugal switch.
Once the inducer is spinning up to speed, 24v circuit is closed.
What happens:
pilot opens, spark sent, ignites right and repeats over and over again.
If I close the feed to gas valve, the igniter continues to spark.
This tells me pilot and flame sensing is working properly.
Turn the gas back on, pilots light up immediately then shuts off and repeat.
All while this drama is happening, the voltage across the module input stays around 25v.
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| | pwned
| "Re(6):gas valve is teh click, clickety click." , posted Sat 2 Feb 01:29
The draft inducer is a brand new. Full control current flows through the thermostat in this circuit, so I monitored current going between R & W at the thermostat connection and I didn't see a current fluctuation that would indicate chattering switch.
I think it's the module. I finally got to the furnace when it was acting up.
Thermostat calls for heat. It activates a relay, then sends 208v to draft inducer activating the centrifugal switch.
Once the inducer is spinning up to speed, 24v circuit is closed.
What happens:
pilot opens, spark sent, ignites right and repeats over and over again.
If I close the feed to gas valve, the igniter continues to spark.
This tells me pilot and flame sensing is working properly.
Turn the gas back on, pilots light up immediately then shuts off and repeat.
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