garage furnace locked up

[Tom7227]

I had turned off the garage furnace but needed to crank it yesterday. When I turned it on the thermostat showed an L and the furnace wouldn't fire. I finally got out a hair dryer and warmed up the thermostat and the furnace fired up. The thermostat is a new Honeywell digital that is maybe a year old, Furnace is a used house furnace that the seller claims to have gone through and cleaned/replaced some of the minor parts.

Is there such a thing as too cold for a furnace? It probably was around 30-32 in the garage and a jug of water on the bench hadn't frozen.

[cavalierowner]

I wonder if the "L" is an indication for a low battery and warming up the t-stat gave a little more life to a battery? Just a guess. I would change the batteries, cheap thing to try.

I've never heard of it being so cold that a furnace wouldn't fire. I have seen a very cold furnace short cycle when it was very cold, but it would always fire.

[Surface Tension]

What model t-stat.

Stuck button, weak battery.

Since it the furnace started after warming the t-stat then I wouldn't look at the furnace as the problem, but.

If the furnace is a high efficiency say 90+ it is a condensing furnace.

There can be moisture trapped in a number of places and freeze. It can start the sequence but not fire up.

[CAMAN]

My guess would be cold battery also.

[daydreamer]

Tom,

I had the exact same thing happen on Saturday. First time I've ever seen an "L" on my digital display. I do have, and have seen a low battery indicator on my thermostat however. I wrote it off as I was turning off the furnace for the day but now I'm curious. Might have to see if I have the manual laying around.

[delcecchi]

Had it happen to the thermostat in the house. I didn't even know that there were batteries in there.

[Chauncey]

I also experience this as I would guess that "L" means low temp as mine spells it out as low, as mine will not kick in if the garage temp is below 32 deg. I trick my thermostat with heat to think it is above 32 and once the actual temp in the garage is above 32 no issues. I do not know if tricking it is a bad idea or not, but I have done it for the past couple of years with no issues. Maybe someone can help answer that question??

[nobody05]

some t-stats act goofy when it's below or clow to there operating temperatures stated in the directions.

[nonteepical]

find your manual online for the thermostat and read up on your thermostat.

[WallEYES]

Tom

My suggestion would be to get rid of the digital/programmable t-stat and go with the plain jane t-stat....heating only....if they are still available...pretty sure they are....yours probably is not listed for your application

[BoxMN]

I have an old school mercury t-stat (a square one) and I mounted it slightly tilting, so that when it is fully set to lowest temp (which I believe is about 50...) it will keep the temp of the garage at a perfect 36. I leave it at that all winter, and bump it up when working or playing out there It does bump my gas bill up a bit, but honestly not as much as I thought it would. Maybe $30 more in Jan and Feb, $20 more in Dec and March. And the cars are always nice and the boat never freezes

[WallEYES]

Tom....I found honeywell makes the round non mercury heat only model number CT87K, or you can go with an anolog stat heat only model CT30A...Both stats are less than 20 dollars