M1MB 090A BW update on burner problem

[jonathan teller]

Okay I checked the gas valve terminals .....They read 1Volt AC untill the main gas valve burner turned on ......then the voltage went up to 25 volts AC..........then the flame started to weaken.....the yellow led started to flash......then the flame went out.....then a second later the voltage droped back to 1 volt.
As to the orifices one is a number 17 the other is a number 36, which one do i use for Nat gas?
Bye for now Jonathan

[Robert]

Nat. Gas = 17


Because the gas valve is a key part in this, need to know input and manifold gas pressures, before, during and after this happens.


WHEN the flame weakened, did the gas valve still maintain 25VAC.


You must determine if this is an electrical or gas problem. Gas valve should get 24-28VAC and it should be continous unitl t-stat is satisfied.


When burner flame weakens and starts going out, is full voltage there at gas valve still ?


If so, then it is the gas valve or orifice/burner or gas pressure problem.


IF the 25VAC is dropping out early, then it is an electrical issue before the gas valve.


Please post answer here by clicking on reply.


Need to keep ALL conversation together, not in several threads for the same problem.



Thanks,
Robert

[jonathan teller]

Ok the gas flame started to weaken definitely before the voltage droped (approx 3 seconds before). So I guess we don't have an electrical problem. Remenber I have just put a new gas valve on and I have tried both orifices with no luck. So that leaves gas pressure . I need to buy a gas pressure tester. Please could you tell me what readings I should expect to get.
Thanks again Robert for all the expert advice!

[Robert]

5"water column inlet and 3.5" water column outlet manifold pressure.

Checking gas pressures is not something I recommend unless experienced in doing so as it can be very dangerous.


At this point I would recommend a Tech be called for safety and to ensure a correct diagnosis.


Can't help further due to increased possibility of a gas pressure and/or combustion problem which can be tricky at times and very dangerous.


Take care and best wishes,
Robert

[jonathan teller]

Ok I'm back ready for some more punishment. The gas pressures are reading 13 wc on the inlet continuosly. The manifold is reading 3.5 when the burner starts and holds 3.5 wc for 5 or 6 seconds untill the flame dies....then the manifold pressure drops back down to zero.
By the way I have just realised that when I replaced the ignigtor assembly I bought a 902661A ignitor. I have just found out that I should have bought a 903110A ignitor. It looks ever so similar to the original one! Could this be the problem? Remember the gas is shuting down before the 24Volts supply dies to the gas valve. Doesn't this indicate that the ignitor I bought is fuctioning normally.
I feel like I'm grasping at straws now!

[Robert]

Hi,

Refer back to my last post, this has reached a non DIY level, really needs a Tech to take it from here.


The savings is not worth the dangers that could come from a wrong diagnosis.



Should have the correct ignitor, they do work different, one from others.



Take care and best wishes,
Robert

[jonathan teller]

Thanks for the reply. I have had three techs working on it and they are taking all your advice seriously. So don't worry it's all quite safe and under proffessional care. The truth is you clearly have more experience on Nordynes than them.......they are running out of idears.
I have one more thought. The flame appears yellow, I wonder if we have a combustion air problem. I can't see any way that the combustion air is entering the combustion chamber. How does it enter?

[Robert]

Hi,

The techniques and steps to locate problem here is not just a Nordyne thing, but a common practice for all units.


Need to locate a Tech who is qualified and experienced to diagnose the problem.


If the Techs there cannot answer the questions you are asking, they need to be looking for different jobs.


Find a Tech who can either diagnose it or stand there and answer the questions and guide you through the process.


This is not DIY any longer or shouldn't be and if a Tech is there and can't answer what you just asked, need to keep looking.


Sorry, but safety is my first priority.


Take care and best wishes,
Robert


This is a safety issue and I cannot divulge any more info on it.

[jonathan teller]

I undertand. Thanks for your help!

[Robert]

You're very welcome, hope you can find a qualified tech to resolve this quickly for you.


Take care and best wishes,
Robert

[jonathan teller]

Success !! It's Florida and 88 degrees outside and I'm running my Nordyne gas furnace and it's over 90 degrees inside now, so i guess this means I've fixed the problem. It was a combustion air problem. The inductor fan was sucking in a mixture of fresh air and exhaust air (incorrectly installed chimney!)
There's not much gas in south Florida so techs here don't know gas.
Thanks again, I couldn't have done it without you!

[Robert]

You did do it without me and against my advice not to. Any real tech in South Florida or elsewhere will have been trained and understand the basics of Heating and Cooling troubleshooting, including gas furnaces.


Glad it is working and nobody, including you got hurt in process.


Take care and best wishes,
Robert