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DangerMouse 09-01-2008 04:23 PM

pilot lights, but not burners
hi again, i have a Nordyne M1GH 077A AW for mobile homes, 4 yrs old. before the winter heating season hits, i figured i'd get it up and running again. last spring, we had a last cold spell after i'd turned off the pilot, and we'd run out of propane anyway. got more fuel, it fired up fine, and heated ok, but after a while, it heated normal and stopped, i turned the thermostat up to kick it in again and all it does is make that darn noise. the pilot is ok, but the burners don't flame on. i really cannot afford a 80 $$ service call (not counting parts) and the call i made to them did not help. ( the last time it did this, i'd simply forgot to set the darn thing to the ON position after i lit it, however this time it was not the problem. the guy said they'd come and look, but as we had no $$$ i told him i'd wait till fall. and it's almost that now, soooo. anything that they might not have told me besides a stupid spiderweb? it worked fine, then did not. that spider was either real fast or that is not the problem. anyone?



8 Ball 09-02-2008 06:06 PM

Up by the blower compartment you may find a manual reset switch. Push the red button.

DangerMouse 09-02-2008 06:14 PM

nope, no red button... i wish it were that easy, but around here, nothing ever is. do we need pics here?


8 Ball 09-02-2008 06:17 PM

Couldnt hurt, do you have a voltmeter? You may have a defective gas valve.

DangerMouse 09-02-2008 06:26 PM

i have a multimeter, but how will that tell me if i have a bad gas valve? and if it is a valve, do they just "die" with no warning? how much/how hard to fix?


8 Ball 09-02-2008 06:44 PM

What do the terminals on the gas valve look like or say, is it Honeywell V800 valve?

DangerMouse 09-02-2008 07:18 PM

the inlet valve? with the red twist on/off? it says 1/2 psi 1/2 is all. don't see 'honeywell' anywhere, just 'robertshaw' and numbers on the switch thingy at the bottom. (sorry i don't know the names for all these things)


SD515 09-02-2008 10:47 PM

Hey DM

Ahh...the ole mobile home furnace with Charlotte's web. Not so much that he was fast, as he was living inside the tubing right next to the nozzle...and got peeved at you for turning on the furnace and distrupted his summer vacation home. I mean with the wife and youngin's and all having a picnic...and then whoosh..a blast of gas went by...he was just trying to stop that air leak.

I have dug out spider webs from the nozzle a few times. Not hard to do at all. Being a 4 yr old furn, I can't imagine a bad gas vavle, but possible. I imagine this furn has a circuit control board (newer PC style)? Is it a 2 wire vavle? You said Robert Shaw, which is one...Honeywell another. Doesn't really matter...especially if it's 2 wire and we just need to check it.

There may be a 'on/off' switch on the vavle itself...should be on, but ya never know....
Look for the wiring schematic. When the furn has a call fot heat it goes thru it's start-up process. Before the g-vlv opens, you should read 0V at both terms of the g-vlv. (It's a 24V system, hot one side, grounded other side. Follow the wires...the 'hot' (source) side will go through limit switches first.) Inside the valve is a spring loaded sloenoid plunger that shuts when power is removed. It's possible that is stuck, but not likely on a 4 yr old. When it gets to the point of opening the gas vavle, 24V is supplied to one side of the valve, goes thru the coil and to grnd. If you can hear the valve clicking, it's most likely opening. If you don't get a reading of 24V at the g-vlv, we'll have to trace back to limit switches, etc. If you get 24...then it's time to go a spider hunting. Let me know if you need help with that.

Oops...I forgot you said it has a pilot. Standing pilot?? It's staying on ok? And you have the g-vlv set to 'on'?

SD515 09-02-2008 11:00 PM


Originally Posted by MdangermouseM (Post 154391)
i have a multimeter, but how will that tell me if i have a bad gas valve? and if it is a valve, do they just "die" with no warning? how much/how hard to fix?


Usually die without warning. Easy to change. A simple 2 wire vavle...$100-200 DIY.

DangerMouse 09-03-2008 06:01 AM

"Standing pilot?? It's staying on ok? And you have the g-vlv set to 'on'?" yes, yes, and yes. sure hope it's a spider then, no way can we afford 200 bucks right now. can i check for the spiderwebs first? how easy is that? (as if i didn't know.....)


SD515 09-03-2008 07:14 AM

Did you check for 24 @ valve yet? You can take one of the wires off the vlv and isolate it from grnd...the valve can't open then, yet one of the 2 wires will have 24 when it's doing 'start-up'.

It's easy to pull the burner out. Shut off elect (120V) & gas vlv (the main one on the incoming 1/2" or 3/4" pipe). Using 2 wrenches, disconnect the gas pipe from the valve. In my area, a 2 footer, flexible gas pipe is used between the shut off vlv and the furn vlv, with flared fittings (no need for tape or dope) so you only have to disconnect at the g-vlv and bend the flex out of the way.
Note the position of the wires then remove them...with 2 wires it shouldn't matter where they hook-up, but ya never know. Remove the t-cpl & pilot tube from the g-vlv.
The burner should be held in with about 6-8 pattern. 2 of them hold the g-vlv bracket to the burner & casing, the others hold the burner to the casing. Take the 2 out that hold the g-vlv brkt, and the valve should come out. Be gentle with it. Might as well take the burner out too, and inspect for debris in there since you are this far.
The nozzle screws into the gentle taking it out. Spiders get inside the area behind the nozzle too. Gently with a small pick or paperclip you can break up the spider web and use a low suction vac to get it out. I put a small bit of pipe dope on the nozzle at re-assembly. You don't want that plugging up the gas flow either. No dope on the pilot tube. No dope on the flared fitting of the gas line. Check your gas fittings for leaks with bubble test...liquid soap works too.
More questions??

DangerMouse 09-03-2008 07:35 AM

dangit, now i can't get the pilot lit.... will the ac voltage read still if no pilot? probly not, huh?


DangerMouse 09-03-2008 07:53 AM

1 Attachment(s)
ok, here's what i'm looking at....


SD515 09-03-2008 08:37 AM

Maybe. At least for a test...on the 'hot' wire. Check the schem or follow the blue & blk will make it's way to grnd...the other goes thru limit switches first...that should be the 'hot' wire. If you follow the hot wire thru the lim sw's, you find the start of that circuit, and can check continuity of the lim sw's and circuit. They should be closed. Even though the pilot doesn't have a flame, the furn should go thru start up, and send 24 to one side of the valve, though it won't open the main.

The t-cpl creates a small voltage when heated..that voltage holds open the pilot valve inside the g-vlv. I'm not exactly sure (but dammit...I'm gonna find out as soon as I get an old valve I can tear apart) how the pilot lets the gas thru the main. I suspect either it opens a passage way for the main, or closes the main solenoid circuit, to allow the wire terms to connect to the solenoid winding. Either way...the furn doesn't know if the g-vlv is just sends 24V to the valve...and either opens or it doesn't.

Was the pilot a good strong flame?? If not, the pilot tube &/or nozzle might have a bit of debris in it (the pilot nozzle has a very small careful not to enlarge it if you clean it). Is the t-cpl 4 yrs old too? The t-cpl might be weak (or have 'carbon sediment' built up on it) and not sending a strong enough signal to get the main to function properly.

When taking the burner careful of the gasket (burner to casing).

I have to head to work now...but will catch up with ya later tonight. Good thing you're doing this when the weather is warm and not 0 degrees out !!

DangerMouse 09-03-2008 08:41 AM

that's the plan... fix it NOW before it's NEEDED... =o)
will try to do some of this today. will keep you all posted.


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