Lennox 80MGF Gas Valve Terminal Connection Issue

1029 Views 5 Replies 3 Participants Last post by Peter78, Nov 30, 2021

Fugue

Discussion Starter · Feb 28, 2020

Hi All,

I have a Lennox 80MGF3/4-100A-1 with a White-Rodgers 36E36-278 Gas Valve.

The furnace has been frequently going into WatchGuard mode since the burners fail to ignite. I cleaned the flame sensor and it functioned normally for a few weeks then started having the same issue. I would turn the furnace off/on repeatedly until it finally ignited.

During recent troubleshooting I was testing connections and moved the wire plugged into the C2 terminal on the gas valve. The burners immediately ignited and everything functioned normally for another week. The next time it failed to ignite, I simply moved the connector slightly and it worked for days again. I cleaned the contacts and confirmed a good connection.

It failed again today. I noticed that moving the connector slightly will either turn on or off the gas flow.

Is it the connection causing the issue or am I sending a signal when I move the wire into a dead spot that temporarily resets something and allows the furnace to run for awhile?

What are the chances that it's a loose connection in the terminal block itself?

I'm going to cut the wire back and attach a new spade connector to see if that is a fix but I'm looking for some advise on whether there is a known issue and I should be getting some parts on the way before I'm left stranded without heat.

Thanks,

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Fugue

Discussion Starter · #3 · Mar 1, 2020

Hi Yuri,

Thanks for the reply and the tips. I put my multi-meter on M1, the wire and C2 on the terminal but it didn't show any voltage even when the furnace called for heat.

I cut back the wire and put on the new connector and was surprised how loose the old one was compared to the new. The furnace has been working and firing up when it gets the demand. This is not unusual since it has worked for days after fiddling with the connection.

I'll update the forum in a week or if it fails again which ever comes first.

Here's hoping...

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Fugue

Discussion Starter · #4 · Mar 10, 2020

It appears the problem is in the terminal. I replaced the spade connector and cleaned the terminal and plugged it all the way in. It lasted a day. As I was pulling the connector off the terminal the flames came on. I left the spade only half way onto the terminal. The furnace has been functioning normally since.

Probably not a loose solder or connection. My best guess is corrosion on the terminal. I'll leave it as long as it's functioning in the cold weather and see what I can do in the summer.

Thanks for the tips.

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