Miller (CMF65) mystery: where's the beef (ignitor)?


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Old 02-11-09, 09:43 AM
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Question Miller (CMF65) mystery: where's the beef (ignitor)?

An entire day online (dial-up--working at half speed since last ice storm!?) only to learn: how easy it is to replace your own ignitor but minus 1 image, video, or explanation re WHERE this thing is?

Which part do I remove to access it -- with a gas appliance, I'm leery of unscrewing/unsealing anything involving combustibles yet even I can guess the ignitor's behind/inside the weldment cylinder where the fuel flows into the heating chamber?

Can anyone resolve this for me (prevent yet another repair bill, which I now know is MORE than the price of 3 extra ignitors) ...even a link to a photo or schematic of the CMF65/80 PG DI innards would do the trick.
 
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Old 02-11-09, 01:38 PM
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I can't find much info online but from what I remember about the cmf furnace they have a standing pilot and not an ignitor.
Maybe just need to light the pilot. Pics would help.
 
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Old 02-11-09, 03:45 PM
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CMF Ignitor

On page 19 of this pdf refer to figure 4. http://www.nordyne.com/literature/067a.pdf

Removal the two 3/8" head screws will detatch the gas valve from the buner. Most moblie homes have the gas valve connected with a flex line. If yours is that way, you don't have to disconnect the gas, otherwise shut off the gas & disconnect the gas valve from the piping.
Once the gas valve is out of the way, there are 2(?) 1/4" hex head screws holding the plate to the burner tube. Remove these screws & gently pull off the plate. If I remember correctly the guts of the burner will come out with removal of the plate.

Be VERY careful when reinstalling the burner. That ignitor is more fragile than egg shell.
 
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Old 02-12-09, 12:46 PM
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Red face UNscrew the fuel relay pipe?

TY GRADY for holy graille link: the photo of pulled out pipe/venturi cap/tube section confirms what I thought, only it also includes the valve?

My Miller pipe is a mirror of the manual pic: rigid, not flexible ...leading me to assume you loosen the pipe's (clearly threaded) valve housing to push the lid (with attached pipe intact) aside for access. I now see I have to pull the entire lid (pipe & interior tube still connected) out---still, the only way I can see to do this is to UNSCREW the pipe from the above valve entirely detaching it (plus lid & tube)?

So is the threaded pipe MEANT to be loosened & re-tightened (for this very purpose) or will doing so break a permanent seal (create a gas leak)? If so, then there must be ANOTHER trick for safely pulling the venturi cap/tube assembly out that doesn't involve the rigid pipe or soldering?
 
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Old 02-12-09, 01:34 PM
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Gas Valve

There should be a union in the piping & a shut off valve upstream of the union. It might be easier to explain if I could see a couple of pictures of YOUR burner & gas piping. You can post pictures on photobucket.com or similar site & provide a link here.
 
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Old 02-14-09, 07:25 AM
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CMF65 schematic

Grady--as per request, posted burner assembly of my model (added gas line in & labels)....

It would appear I have to remove the entire works starting from the gas valve (not the manifold pipe section)....but the same concern applies: I do not recall the repairman ever soldering to reseal this deconstruction back together, so it MUST be safe to (turning the line in valve lever OFF) unscrew the line in from its connect to the GAS VALVE period?

OR detach the manifold weldment & burner orifice from the center of the venturi cylinder lid/cap (which, again being rigid, still suggests needing to loosen the rigid pipe threading from the valve in order to swivel that section to the side & pull the venturi burner tube out?

Pictures by eye_fotos - Photobucket

URL: s662.photobucket.com/albums/uu343/eye_fotos/
 
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Old 02-14-09, 07:56 AM
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Gas Line

Of what material is the gas piping made? If copper, is it tubing or pipe?
A way to tell is by how the shut off valve & gas valve are connected to the piping. If there are cone shaped nuts, it is tubing & the nuts will swivel on the tubing. If there is any indication of solder, somebody really screwed up.
 
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Old 02-14-09, 09:04 AM
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It looks to me like you could follow the first option given in the diagram and disconnect the burner weldment which looks like it screws into the burner manifold. That looks like it would allow you to move the gas valve out of the way and remove the burner and igniter assembly.

Hard to tell for sure, but it might be worth looking at carefully.
 
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Old 02-14-09, 12:14 PM
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cone? tube v pipe?

da plot thickens!

First off if soldering is out of the question then all these connections are threaded; designed to be both unscrewed & resealed well enough to maintain the fuel flow (without leaks)

Secondly (looks like I'll have to find the camera cause I can only continue to guess here): 1)I believe the gas line is copper, I imagine the difference between a 'tube' & 'pipe' would be diameter therefore I'm goin' with door number 2 = PIPE (pretty much the size of a water pipe), & 2)Cone v regular Nut: if by cone you mean the nut coves in to fit the round pipe then cone it is for all the nuts have this feature, in this order = first there is a coved nut connecting the pipe to the on/off lever valve, then a 2nd coved nut connecting the lever valve back to like a 1/4" pipe extension, immediately above that is a 3rd coved nut connecting an elbow that threads directly into the gas valve (with teflon wrap visible) .....wait.....

This sequence makes me wonder if [so long as the line-in lever valve OFF is enough protection] the easiest method would be to unscrew the 2nd 'coved' nut immediately above the lever valve (freeing that side), unplug the 2 wires between the gas valve box & the ignition box, then unscrew the 2 hex nuts on the rim of the venturi lid, which should render that entire section ready to be pulled out intact?
 
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Old 02-14-09, 12:47 PM
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Nuts

Shut off the lever valve (handle will be across the pipe rather than paralell to it). Hold the valve BODY with one wrench while disconnecting the nut on the downstream side. From there you should be able to continue disassembly.

Upon re-assembly use some soapy water on all fittings to check for leaks after you turn the gas back on. Mix diswashing liquid with water for your soap solution. Use 1 part soap to about 5 parts water. When done checking for leaks, wipe all soap off the fittings & pipe with a wet rag.
 
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Old 02-14-09, 01:32 PM
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Hello Jack----


Frankly, it sounds like you need to be master of more than no skills to do the job at hand. The most important DIY skill is knowing when to call in a pro, and I think that would be the smart move.

In most furnaces, replacing an ignitor is an easy job. In the furnace you have it requires a fair amount of disassembly. I'd say you've Done Your best!
 
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Old 02-15-09, 08:57 AM
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Thumbs up Appreciate assistance!

Grady--TY 4 your helpful advice, the exercise of examining the line-in unions allowed me to 'answer my own Qs': all fuel line connections are threaded ergo a 'screw in/out seal' has GOT to suffice–the critical missing link to reverse-engineer & figure out the 'secret handshake' necessary to access this Miller's compact innards.

I think I'm going to combine that with Seattle's cautionary say: Disassemble it myself before repairman arrives: cutting that extra 15 minutes labor (the check-list inventory they insist on before conceding the customer's diagnosis) off the bill. Then watch him reconnect like a hawk, store the soap test info, and DIY thereafter!

I've learned more about furnaces then I wanted to know but FYI: for a city girl rural homeowner, I've had enough aptitude to handle more handyman jobs then ANY guy I know which is why I use these boards full of guys who DO know
 
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Old 02-15-09, 10:57 AM
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Jillofnone

We've been discussing how to replace the ignitor but neither SP or myself ever asked "how do you know it's bad?". Do you have a multi-meter & know how to use it? There is a possibility the fault is not the ignitor.
 
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Old 02-16-09, 12:24 PM
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Sorry in advance: I don't know how to shorten this saga

It could be voltage (I’ve only a meter-less tester) but in the realm of the usual suspects it’s always the ignitor (exhibit A-D: regular cycle processing clicks, safety checks, abortive shut-off, & dark port), plus it’s lasted over 3 years (which I now know—not to refute the great Hank Hill—is impressive for the dirtier burning propane’s propensity to reduce this part‘s 7+ yr life span by leaps-n-bounds).

Every professional repair begins with replacing it; twice that included the ignition module, once a warped heat spreader (cheap part, costly labor) but those were direct results of installing 1)a frozen ignitor that exploded sending a reverse serge shorting out the module & 2)the wrong ignitors; repeatedly (5 times over the course of 2 yrs) mistaking #902466 for 902499 (resulting in, among other unhappy events, pipe damage)<--an error yours truly eventually figured out after having the heater inspected cleaned et al & getting no more response beyond the party line (any speck of dust will burn it out) to my inquiring what else could cause so many ignitor failures as to make leaving the house over winter a crap shoot? I’d already been mentioning would it be better to buy direct from Nordyne to get less vulnerable performance (perhaps the compatibles aren’t so compatible)? It was the warped spreader that connected the dots for me; by the time I had to pay to replace that I asked if maybe those universal ignitors weren’t slightly longer, bigger, closer, more susceptible to contact? ... after the 4th replacement in 8 weeks even the repairman began to wonder: eureka, 66 for 99, a simple dyslexia reeking a mountain of migraines (not to mention at least a grand)

Once the correct model was installed, I got over 3 yrs service out of it.....I’d bet the bank it’s the ignitor.

Revisiting this injustice re-motivates: (more confident with Grady's hints [double wrench gas line & soap test]) if I bother to disassemble, may as well install ...if that doesn’t resolve the problem, then I acquiesce to call in the cavalry!
 
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Old 02-16-09, 02:09 PM
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Ignitor

The next time you have $20-30 to spend on tools, pick up an inexpensive multi-meter. You'd be amazed at how much troubleshooting you can do around the house with one.

Given your history of ignitor problems, I would tend to agree the problem is likely with the ignitor but I don't like to replace parts unless I know they are bad.

I don't know if a silicon nitride ignitor is available for that burner or not. Nor do I know what would be involved in conversion if one were available but they are supposed to be lots more durable.
 
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Old 02-17-09, 11:43 AM
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Question round vs flat surface ignitor

Grady--

I am curious: 1)is that silicon nitride model the new round ignitors I spot for sale all over the net? 2)could I theoretically switch out the flat surface for a round ignitor (or would that produce the same woe as all those #902466s did)?

I seem to have (the Miller CMF65's been history for a decade) increasingly limited option replacing HVAC 902499 ignitors; while I see a sea of similar flat surface universals (all 30-50% cheaper), of course neither my discontinued model nor 902499 is included in the compatible lists––yet I could compile a list of other make/models mentioned as 902499 compatible & might be able to broaden my choices by cross-referencing (if that $35 ignitor works in this Goodman model & I locate that model on the 902499 list, it SHOULD work in mine)? Any advice?
 
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Old 02-17-09, 07:02 PM
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Silicon Nitride

Most (all?) silicon nitride ignitors require a different ignition control than the silicon carbide. Most of the silicon nitride ignitors I've are basically a rod. I think the round ones you are talking about are a spiral silicon carbide.

The problem I've had with a lot of "compatible" ignitors is the actual ignitor length (from the ignitor end of the porcelain to the end of the ignitor itself) is just a hair longer than the Miller OEM part. I broke two in about 5 minutes one night & only after getting an original Miller part & comparing it to the "compatible replacement" did I discover the difference of MAYBE 1/16". Just enough to snap the carbide as soon as I pushed the burner end cap on to line up the screw hole.
 
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Old 02-18-09, 07:21 AM
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Red face OK, not veering from the OEM

Asked-Answered: I was hoping there were other facsimiles but I'll stick with the sole HVAC offer---I actually found a genuine MILLER CMF65 ignitor for sale online, only it's $170; over 3 times the price of the Nordyne/OEM 902499, even more than the total bill (part & labor) the repairman will charge!? If the MILLER ignitor REALLY lasted '7 to 10 yrs' it would be worth it, but what with that scary codicil (any speck of dust will destroy the head) dem's just horrid odds!

FYI: by the by, that 1/16" extra length IS why all 5 of the wrong HVACs (902466) worked...for a while (one as long as 4-5 months, one as short as 4-5 days, the rest several weeks)
 
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Old 02-18-09, 04:28 PM
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902499

Once you learn how to replace it, here's a place (with a good reputation) that has them for
 
 

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