We have a Clare Magnasave gas furnace, installed in 1984. Sometimes, when
the furnace starts up, just the blower comes on, but there is no ignition.

So far, I have been able to get it to work by switching off power to the
furnace for a minute or so, and then switching it back on. The blower then
comes on, and a minute or two later, the heat starts.

Everything will work for several cycles of this, but, eventually, it will
repeat.

Any ideas as to the cause?

Bad ignitor? I had mine replaced three times, before I finally got a new
furnace.
-- pj



In article , Joe Lennox
wrote:
We have a Clare Magnasave gas furnace, installed in 1984. Sometimes, when
the furnace starts up, just the blower comes on, but there is no ignition.

So far, I have been able to get it to work by switching off power to the
furnace for a minute or so, and then switching it back on. The blower then
comes on, and a minute or two later, the heat starts.

Everything will work for several cycles of this, but, eventually, it will
repeat.

Any ideas as to the cause?

Are you sure it's the blower that's coming on and not the
chimney exhaust fan? I suspect that it may be the latter.

There are a number of possibilities (assuming that it may be
the exhaust fan that's coming on):

1) Your igniter is bad.

2) Your exhaust fan is bad and isn't producing enough of a
draft.

3) Your chimney is blocked, so the exhaust fan can't produce
enough of a draft.

4) Your pressure switch is broken so the furnace thinks that
the exhaust fan isn't producing a draft when in fact it is.

Your first step in figuring this out is to make sure you
understand the difference in sound between the exhaust fan
and the blower :-). My apologies if you already understand
the distinction.... some people don't.

If your exhaust fan comes on when the furnace decides that
heat is needed, and then a little while later you hear clicks
from the furnace, and then it starts the cycle over, then
it's probably the igniter -- the clicks are the furnace
turning on the gas and trying to ignite it.

If your exhaust fan comes on but then there are no clicks, or
there's just one click as the fan shuts off, then it's one of
the other three possibilities. If the exhaust fan sounds like
it's working just fine, it's probably one of the last two.

The executive summary of all this is that you should have
a trained professional come out and look at your furnace.
You don't want an amateur messing around when there's gas,
fire and carbon monoxide involved.

"Joe Lennox" wrote in message
news
We have a Clare Magnasave gas furnace, installed in 1984. Sometimes, when
the furnace starts up, just the blower comes on, but there is no ignition.

So far, I have been able to get it to work by switching off power to the
furnace for a minute or so, and then switching it back on. The blower then
comes on, and a minute or two later, the heat starts.

Everything will work for several cycles of this, but, eventually, it will
repeat.

Any ideas as to the cause?

This is Turtle.

You have a Fan / Limit Switch sticking on the gravity vent type furnaces. Next
time you have this slap the face of the furnace and you will see it stop
blowing. Have you a hvac service man come check it out and clean the switch but
I suggest he might change it out to a Honeywell only type switch for other
brands seem to have trouble like this again even with the new one.

Fan / Limit Switch problem.

TURTLE

"Jonathan Kamens" wrote in message
...
Are you sure it's the blower that's coming on and not the
chimney exhaust fan? I suspect that it may be the latter.

There are a number of possibilities (assuming that it may be
the exhaust fan that's coming on):

1) Your igniter is bad.

2) Your exhaust fan is bad and isn't producing enough of a
draft.

3) Your chimney is blocked, so the exhaust fan can't produce
enough of a draft.

4) Your pressure switch is broken so the furnace thinks that
the exhaust fan isn't producing a draft when in fact it is.

Your first step in figuring this out is to make sure you
understand the difference in sound between the exhaust fan
and the blower :-). My apologies if you already understand
the distinction.... some people don't.

If your exhaust fan comes on when the furnace decides that
heat is needed, and then a little while later you hear clicks
from the furnace, and then it starts the cycle over, then
it's probably the igniter -- the clicks are the furnace
turning on the gas and trying to ignite it.

If your exhaust fan comes on but then there are no clicks, or
there's just one click as the fan shuts off, then it's one of
the other three possibilities. If the exhaust fan sounds like
it's working just fine, it's probably one of the last two.

The executive summary of all this is that you should have
a trained professional come out and look at your furnace.
You don't want an amateur messing around when there's gas,
fire and carbon monoxide involved.

This is Turtle

In 1984 Vent fans type furnacers were rare.

TURTLE

"TURTLE" wrote in news:32r08lF3p4kosU1
@individual.net:


In 1984 Vent fans type furnacers were rare.

TURTLE

In every furnace I've seen, the blower is activated by the fan controller
in response to the heat exchanger temp passing the "on" setpoint. If the
burner doesn't ignite, the blower will never come on. I'm sure that's what
lead the poster to which you responded to assume that the "blower" the OP
reported must be a forced draft fan.

On Wed, 22 Dec 2004 07:52:15 -0600, David W. wrote:

"TURTLE" wrote in news:32r08lF3p4kosU1
@individual.net:


In 1984 Vent fans type furnacers were rare.

TURTLE

In every furnace I've seen, the blower is activated by the fan
controller in response to the heat exchanger temp passing the "on"
setpoint. If the burner doesn't ignite, the blower will never come on.
I'm sure that's what lead the poster to which you responded to assume
that the "blower" the OP reported must be a forced draft fan.

I don't know the terminology, but a fan comes on first, then if things are
working, there is a click, and the gas ignites; a minute or so later
another fan comes on to blow the hot air into the ducts.

The first fan is blowing moisture-laden air through a 3-inch plastic pipe,
to a vent in the wall of the foundation.

When things aren't working, the first fan comes on, but there is no click
and no ignition.

One gentleman said it needs a new ignitor, which sounds reasonable to me.

Thanks for the replies.

Joe Lennox writes:
When things aren't working, the first fan comes on, but there is no click
and no ignition.

One gentleman said it needs a new ignitor, which sounds reasonable to me.

If there is no click and no smell of gas, then the furnace is
never getting to the point of trying to use the igniter,
which means that it's the pressure switch or something like
that, not the igniter.

For some reason the furnace control module doesn't think it's
safe to turn on the gas and ignite it.

If that's the case, then I'd strongly advise you to pay a
professional to troubleshoot and fix the issue.

In article ,
David W. wrote:
"TURTLE" wrote in news:32r08lF3p4kosU1
:


In 1984 Vent fans type furnacers were rare.

TURTLE

In every furnace I've seen, the blower is activated by the fan controller
in response to the heat exchanger temp passing the "on" setpoint. If the
burner doesn't ignite, the blower will never come on. I'm sure that's what
lead the poster to which you responded to assume that the "blower" the OP
reported must be a forced draft fan.

Not mine. It seems to be a time delay. When my ignitor has failed the
fan will still come on - the main blower - after a delay. Blows cold
air since the gas didn't ignite and the valve has gone off but it still
wants to run the main blower. This is a 90's system BTW.
--
---------------------------------------------------------------------_------
|Bob Rahe, MIEEE, (RWR50) / ASCII ribbon campaign ( ) |
|Delaware Technical & Community College / - against HTML email X |
|Computer Center, Dover, Delaware / & vCards / \ |
----------------------------------------------------------------------------

"David W." wrote in message
. ..
"TURTLE" wrote in news:32r08lF3p4kosU1
@individual.net:


In 1984 Vent fans type furnacers were rare.

TURTLE

In every furnace I've seen, the blower is activated by the fan controller
in response to the heat exchanger temp passing the "on" setpoint. If the
burner doesn't ignite, the blower will never come on. I'm sure that's what
lead the poster to which you responded to assume that the "blower" the OP
reported must be a forced draft fan.

This is Turtle.

My terminology may have miss lead you here. When I say a vent fan type furnace
it is a vent fan used just to pull the flames through the fire chamber and not
to blow air in the house. The main blower does this. On these furnaces you have
to have the vent fan running to get the flames to go through the fire chamber.

TURTLE