Furnace smell and stains

The furnace pictured smelled upon approach at the covers top louver. The 8800 also lit up while approaching the manifold. So did my nose. Does anyone know if the gas valve within the unit could be stuck open slightly or not closing all the way? Also there is signs of moisture like deposits below the manifold. How common is this and does anyone have similar experience with seeing that?

There seems to be a lot of gas pipe connections. Did you check all the joints with a “gas leak detector”?

Welcome Kevin !!


Yes. I agree lots of connections. I walked the sniffer around each slowly but now increase until I went to the manifold and the tester lit up high.

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Yes I used the TIF8800

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Report what you see and do. Do not guess. IMHO


Sounds like a leaky valve, dangerous stuff, should be addressed at once.


And a union to boot! Because they went left instead right.


There is a union below. Not the most convenient union but there is one.

Welcome to the forum, Kevin, Enjoy!!


Must have been a sale on fittings! :grin: Welcome aboard, Kevin!


Yes, I see it, and it should not be there… there should be least amount of connections inside the cabinet close to the source of a spark. The more connections the more chance for a leak.


Diagnosing for an in-law. HVAC has been called scheduled for Monday. I have visited the vacant home twice in the last two weeks with the smell prominent both times. Thanks for the help!

Gotcha! Misunderstood you. Thanks!

I used to install furnaces, and did lots of gas piping…these look like a nightmare…can’t see how some of the nipples could ever be tightened enough. I think they relied on the pipe dope more than tightening some down…but yea, just report what you see and test. Recommend further evaluation…

Hi Scott, just wondering if the gas line should be running along the exterior as opposed to what you see in photo or does it matter?

End shot burners do smell at shutdown.
Was this Natural Gas or Propane?
The manifold to the gas valve bleeds off slowly after shutdown and there is no flue vent draft in an induced draft unit to suck it up the the flue pipe.

As for the condensation in the burner area; this is normal condensation when the furnace is in a cold ambient location. It occurs most often in the summer when the AC is operating.

If the unit operates normally, none of this should be a concern for a Home Inspector.

Use caution when calling out a gas leak with a leak detector. Some utilities will raise hell over you doing this when they are the ones called about the leak.

From the pic it’s hard to tell why the line was brought in from the left side. Sometimes you need to, & sometimes you pipe it to the other side, however, the decision to go down, and go under the valve and inducer motor has made for very difficult and questionable adequate connections since some look nearly impossible to get a wrench into to tighten them enough. I’m not sure why the installers didn’t just go up and over the valve… same with the union… better to have it outside the case.

Thanks for the reply Scott. Makes you wonder if it was uncle Bob who YouTubed it. Cheers

All those fittings along with pipe dope all over the place looks like an armature installation and if you are smelling a gas leak, I would just call it out. You will sometimes get a gas smell at shutdown and could be normal but when you see a messy install like that, I would bet there is a leak at one or more of those joints… Could even be intermittent and hard to pin down where. If you wanted to diagnose where and confirm, Soap test would be better than trying to confirm or rule out with a detector.