Bad Honeywell S8600 Ignition Module?


  #1  
Old 03-28-09, 04:11 AM
R
Member
Thread Starter
Join Date: Mar 2009
Location: Olympia, WA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Bad Honeywell S8600 Ignition Module?

I have a Heil gas furnace (vintage 1992). The furnace runs continuously, blowing cold air. I know that the furnace has a spark ignition, however a flame is present that resembles a pilot light.

I have discovered that tapping the relays in the ignition module (cover removed) with a screwdriver handle will cause the main burner to light for a few seconds (maybe 10 sec). But it will not remain on.

I'm thinking that the solution would be to replace the S8600 with the S8610U3009 (updated part). Am I on the right track?

The house is for sale so I would like to fix the furnace and not replace it.

I've spent several hours reading through the posts here and though I can find similar issues, none match exactly.

Thanks in advance.
 
  #2  
Old 03-28-09, 04:22 AM
hvachelp's Avatar
Member
Join Date: Mar 2009
Location: illinois
Posts: 22
Upvotes: 0
Received 0 Upvotes on 0 Posts
before you start replacing your module maybe taking cover off is not your problem. Have you tried cleaning your flame sensor?
 
  #3  
Old 03-28-09, 04:31 AM
hvachelp's Avatar
Member
Join Date: Mar 2009
Location: illinois
Posts: 22
Upvotes: 0
Received 0 Upvotes on 0 Posts
What you are describing could be a flame sensor, furnace fails to light so fan will keep blowing. Lot of furnaces after trying 3 to 4 times and fail to light will go into lockout. Flame sensor is located usually on opposite site of your ignitor (single wire, porcalin base ) clean it with steel wool.
 
  #4  
Old 03-28-09, 10:34 AM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
In my experience the Honeywell S8600 is the best and most reliable way to light a gas burner ever.

There is no separate flame sensor on this system. Any part of the metal pilot assembly serves as a flame sensor. While I've never found one of these pilot burner assemblies failing to work because they are dirty, anything is possible, so brushing the metal pilot assembly that is struck by the pilot flame might be worthwhile.

The most likely cause of the problem is a pilot orifice that is dirty and needs to be cleaned. Disassembling the pilot burner and cleaning the pilot orifice, or better yet, replacing it is recommended. (The pilot orifice tends to be hard to clean).

Also, usually there is a ground wire going to the pilot burner. Check that to make sure it is intact and in good condition.

The correct test to determine the problem is to measure the microamps between the ground wire and the ground connection on the ignition module. A typical read would be 5-6 microamps when the pilot is lit. If it's 1 microamp or less, you have a problem with the pilot assembly.

Again, the most likely problem is a dirty pilot orifice.
 
  #5  
Old 03-28-09, 12:48 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
I'm supposing that the sparks stops after the pilot light is lit? That suggests that the flame rectification circuit is working.

I'd also check to see if there is 24 vac to the main burner gas valve circuit MV/PV-MV. If there is, the gas valve may be bad.



Seattle Pioneer
 
  #6  
Old 03-29-09, 02:58 PM
R
Member
Thread Starter
Join Date: Mar 2009
Location: Olympia, WA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks so much for the quick replies

I'll print these suggestions and have them on hand as a guide. I've moved and don't have access to the internet at the old house. I'll let you know what I find out.

Thanks
Ron
 
  #7  
Old 03-31-09, 06:06 PM
R
Member
Thread Starter
Join Date: Mar 2009
Location: Olympia, WA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ok, first I’d like to say thanks for all the help.

The furnace is now working!

The source of the problem was the ground wire that connects the ignition module to the pilot burner. I think this wire performs the “flame sensor” function. From 17 years of use the wire had broken where it was crimped into the terminal that was screwed to the pilot burner bracket. When I removed the assembly to clean it, the wire just fell off (I didn’t put any tension on it at all).

I’m not sure that the ground wire was my only problem. In the two hours it took for the temperature in the house (~2,000 sf) to rise from 48f to 58f, the burner shut off about 8 times. 2-3 of these times I believe the furnace reached the high limit switch and automatically restarted after an approximately 5 minute cool down. The other times the gas valve would start clicking and would immediately restart.

I know I just put the furnace through a “stress test” asking it to run continuously for 2hrs. My question is … Are all these restarts normal? I’m thinking that the restarts due to the furnace reaching the high limit shut off are normal. But what about the other 5-6 restarts? Is this excessive?

I have now repaired the ground wire, cleaned the ‘sparker’ and the pilot jet. I have removed and reattached all the spade connectors on the ignition module and the gas valve. The voltage at the MV/PV-MV is 11 – 12vdc when starting and ~1.5vdc when running. (I could not get an ac voltage reading)
 
  #8  
Old 03-31-09, 06:26 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Good catch on the broken ground.

Regarding the clicking gas valve - that is likely due to the pressure switch operating in a marginal vacuum range, where it opens and closes, and instantly causes the gas valve to likewise open and close in this flutter fashion. Seen this many times in service calls. Cause could be something as simple as condensate water that cannot get out of the secondary heat exchanger, caused by some condensate line clog, in the lines or the trap. Blow them all clear.

Also could be caused by a scum that is in where the pressure switch vacuum tube plugs into the inducer motor. Take off the tube and ream out that nipple and hole right on into the inducer housing.

And marginal pilot flame detection could also cause this. Even though you fixed the wire, you still need good flame contact with what the flame contacts so it can make it's way through the metal and to the ground. But the pressure swtich test I suggested will let you know if it is pressure switch related or pilot related.

If you have a voltmeter, you can easily test my theory that when the gas valve clicks, see if you only momentarily lose power to the outgoing wire(not both wires) of the pressure switch. Or, if you have a 3-wire pressure switch, it be that you lose power from the NO(normally open, but that closes when the inducer is running) wire/terminal to C(common).

It also still could be caused from a marginally weak pilot flame or insufficient ground through metal pilot assembly to ground wire to control module. But by conducting that pressure switch test, you will know if you have a vacuum issue or pilot/ground issue.
 

Last edited by ecman51; 03-31-09 at 06:36 PM. Reason: added last paragraph.
  #9  
Old 04-03-09, 07:35 PM
R
Member
Thread Starter
Join Date: Mar 2009
Location: Olympia, WA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
OK... Apparently i,m trouble shooting several problems...
I went back to the house only to find the ignition module in lockout and the fan on blowing cold air.

I re-did the all the ground wire and pilot assembly contacts, making sure that they were clean and free of corrosion.
I also checked the vacuum hose to the pressure switch. I found the end that attached to the blower to be hard and brittle and it broke off when I touched it. I cut it back and reattached it after checking for and blockages.

The furnace has been running without problems for for two days now. I'm not sure that its completely fixed, but it looks promising so far.

Thanks for the tips.

Seattle pioneer asked if the MV-MV/PV voltage was 24vac... I apparently didn't have the multimeter set right. After finding the correct settings, I did read 25.2vac. Is this something to be concerned with?
 
  #10  
Old 04-04-09, 12:42 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Originally Posted by RonVTR
Seattle pioneer asked if the MV-MV/PV voltage was 24vac... I apparently didn't have the multimeter set right. After finding the correct settings, I did read 25.2vac. Is this something to be concerned with?
No. That is a voltage within the parameters it could be.

If your furnace acts up again, let us know. Maybe that tube was crunchy and letting some air slip in. Since the vacuum draw is so tiny, measured in water column rating (I think it can be like .9 w.c.), that any even slight introduction of outside air will kill the vacuum created by the inducer.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: