Why is my heat pump blowing out cold air
Furnace Not Blowing Hot Air - Easy Fix
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hey guys Jay here with word of advice TV
so today after lunch my wife calls me up
at about one o'clock and tells me I just
came home and it's 61 degrees in the
house I'm thinking shoot I'm only going
to come home at like 6 o'clock it's
gonna get even colder by then so I tell
her okay just go down to the furnace and
tell me what it's doing and she says
there's no flames that glow thing is not
glowing nothing's really working up on
top but the fan is running so I tell her
all right can you look in the sight
glass on the bottom door and tell me if
you see anything that she says yes I do
see a light inside the sight glass I
tell her okay that's great now if you
could just count how many times as
blinking and let me know and she was
counting it you know one two three four
pause one two three four so I was
blinking four times so on my control
board I have a diagnostic chart it's
either gonna be on your board or in the
back of your furnace door in fact let's
just take them off usually on most
furnaces the diagnostic chart that
explains your error culture fault codes
will be somewhere on the back of your
furnace door and mine all I have is a
schematic as you can see but on most
furnaces that diagnostic chart will be
on the inside of the furnace door in my
case most furnaces don't have it like
this but on mine my diagnostic chart is
right on the control board itself and on
my board it says here that four flashes
means that my thermal protection device
is open
and just so you know I'm different
furnaces that will be called different
things for example your board might say
or your diagnostic chart might say that
your upper limit is open or you have a
limit lockout or it will say high limit
open something to do with the limit or
in my case it said thermal device but it
was talking about the high limit which
is right here on most furnaces it will
look like this it's a black square like
that and that is your thermal device or
your high limit switch so if your
furnace is ever overheating this switch
right here shuts down the furnace and on
some furnaces instead of a rectangle
like this it'll be either black or brown
sometimes it'll be a bi-metal switch and
it'll be just like a round little thing
I'll add a picture so you can see what
that looks like so it's blinking four
times right which means my high limit is
open and I'm thinking okay maybe if she
resets the power and it's perhaps it's
in a lockout if it overheats so many
times the furnace will go into a lockout
where it just sits there for three to
five hours and just does absolutely
nothing so I tell my wife all right shut
down the furnace power switch leave it
off for like five seconds and turn it
back on does the furnace do anything
different so she did that turns the
power back on and still nothing you know
nothing up here works but the fan turns
on and that control board is still
blinking four blinks
so what happened in my case is my
furnace was overheating for probably
like a week or so by now I was actually
forgetful and I forgot to change my
filter for probably like two or three
months I usually change it every month
and a half and my filter it doesn't look
that dirty but I guess we've been
burning some candles lately and the
residue from the candles for some reason
just plugs these filters up with this
waxy feeling stuff I guess it's
literally just the wax from the candles
but that really plugs up filter so if
you burn a lot of candles make sure you
replace their filters every month but
anyways I forgot about my filter for
probably like three months so my furnace
was overheating and the way that switch
works it's two different kinds of metals
and they're made out of different
materials so if for some reason your
furnace is getting too hot one of those
metals will
warp and separate from the other one and
as you can see right here the switch
only has two wires so you know you're 24
volts will go into one side and that
switch is normally closed which means
normally operating furnace this switch
should always be closed power will go in
one side and then come right back out
the other side but if it's overheated
and that bi-metal opened up then that
switch is going to be open and not allow
the circuit to go through and if this
limit switch is open then your igniter
will not glow and your gas valve will
not open but anyway back to my story so
my wife told me is blinking four times
she tried resetting it nothing's working
so being the good technician that I am I
tell her okay no problem
take out the doors and I'll walk you
through it I'll tell you what to do
you'll get it fixed in no time
unfortunately my wife was not as
enthusiastic about digging into the
furnace as I was so she told me no
thanks I'll just put on an extra pair of
socks and wait for you to come home so
of course you know later on that's 6:00
6:30 I come home and within a couple of
minutes I got my furnace back up and
running and in a little bit I will tell
you how I did that but before I do that
just real quickly for those of you who
are interested I'll just show you how to
check that switch with a meter if you
wanted to there's two ways you can check
it one way is to check voltage which is
what I prefer I usually prefer to check
voltages more than resistance but you
can also check the resistance or a
continuity since it's a switch so if you
set your meter to let's get my
flashlight so you can actually see it if
you set your meter to continuity which
is that right there that symbol and
mines magnetic so I'll just flip it
right on here somewhere or maybe even to
the inducer motor and then and then just
unplug the wires both of the wires going
to your high limit switch so you just
have the terminals and with your meter
set to continuity put both leads on both
terminals like this
as you can see my meter is beeping which
means this switch does have continuity
now if this switch was oh L like you see
rate on my meter like that that means
that switch is open or you can just
check the resistance that Omega symbol
or the ohm symbol almost the same thing
put your leads on both terminals except
when you're checking resistance there
won't be any beeping as you can see I
have about 1.8 around 2 ohms of
resistance which is normal for this
switch so I know my switch is closed and
like I said previously it's a normally
closed switch so you should have some
kind of resistance or continuity between
the two terminals so that's how you
check resistance and continuity but the
way I prefer to do it is to check
voltage so you do need to have the power
on for this so turn the power on my
thermostat upstairs is calling for Heat
I had my power switch off the whole time
so the burners aren't on while I'm
talking so there it goes my inducer
motor my igniter is gonna start to glow
my pressure switch is closed so by this
time my high limit should have 24 volts
going through it so if I go from one end
to the other if you look at my meter as
you can see I have zero volts and for
those of you that don't know a switch is
literally just that it's just a switch
almost like a piece of wire so if the
switch is closed you won't have any
voltage drop so no voltage it will be
zero but if that switch is open you will
have around 27 volts so for example if I
keep one lead on one terminal and put
the other lead to ground and what I mean
by that is just any screw that's
attached to the furnace cabinet
so for example I'll just go right to the
sky limits true as you can see I have 26
point 4 volts coming in and if I go to
the other terminal
like that I have 26.4 volts coming out
that way I know that the switch is
closed so once again when checking
voltage you just put your leads on both
terminals and if the switch is closed
you'll have zero volts if it's open you
will have twenty six volts so that's how
you check it with the meter now on to
the part of how I actually fixed it
fixing this is actually pretty easy so
basically that switch is stuck open a
lot of times if you just smack it a few
times that'll be enough to cause those
two metals to come back together so in
my case I just took a screwdriver and it
was enough to just whack the limit just
on the faceplate right here just a
couple whacks or good whacks
I just want pam pam pam pam pam i reset
my furnace turned it back on and
everything lit right back up so it was a
really quick fix now sometimes if it's
really stuck open you have to take that
switch out and I'll just show you quick
so you know what it looks like inside
sometimes you have to take it out and
give it a couple of good whacks with the
high-limit out and I have had a couple
times where no matter how hard you hit
it the thing does not close back up in
that case you just have to replace the
high limit so anyways I took out the two
5/16 screws and let's take my switch out
this is what mine looks like it has
usually it'll have some insulation on
the inside and then here's that bi-metal
part that I was talking about you can't
really see the two metals inside they're
all internal but basically here's the
sensor which is usually facing downwards
and on most high limits this will just
be two prongs mine has a plastic casing
it's just an older furnace not a lot of
furnaces will have this plastic casing
and some of them there's different
lengths some of them are a lot longer
maybe like up to here but yeah this is
the high limit it's nothing too
complicated
so if hitting it on the face does not
close it up for you you can try taking
it out and just just
against your furnace or against the
floor not too hard just firmly - trying
to close that back up and almost all the
time that is enough to close that thing
back up and your furnace will start back
up well and that's how you manually
reset that high limit switch in my case
it was a dirty filter and most of the
time that's what it is your filter is
just dirty but there is a lot of other
things that can cause your furnace to
overheat I won't go into that in this
video but I am planning and making a
video right after this one on ten
reasons why your furnace can overheat so
if your problem is not a filter then you
can go ahead and check that video out
for more ideas of why your furnace keeps
overheating and just one more thing I
want to mention a lot of times people
they read their code and it says high
limit open the first thing they do is
replace that limit switch just so you
know it's very rare that that limit
switch fails doesn't happen a lot at all
usually it's just doing its job and it's
opening up because the furnace is
overheating so you have to figure out
why it's overheating and get that fixed
or cleaned up and that is all I had for
this video today I hope you found this
information useful thank you so much for
watching this video don't forget to mash
that like button on the way out and
we'll see you next time and for those of
you that are still here I want to show
you some brownies that a customer gave
me he tells me hey you want some
brownies they're high in fiber and low
in calories and low in fat they're very
great you want some and I say yeah sure
I'll have some so he brings him out to
me and he hands me these brownies
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