Furnace clicks off and on


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Old 02-28-07, 10:23 AM
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Furnace clicks off and on

Hopefully someone can point me in the right direction.

I live in a mobile home and recently my furnace has had a weird problem. My furnace will light properly when the temperature drops, blower will come on, then randomly the furnace will quit and restart. It may restart one, twice or three times, very random. Once it goes through this cycle, it runs normal and shuts down on it's own once the proper temperature has been reached.

Thought it may be dirty air filters, yes they are dirty, but taking them out of the equation does not make a difference, ie....removing them.

One thing I noticed was that when I manually turn the furnace on from the t-stat, the furnace does not reproduce the click on-off sequence, and runs it's normal cycle. When I let the t-stat turn the furnace on by itself through a temperature drop, I seem to have problems with the furnace shutting down and then restarting within seconds. Does this sound like a t-stat issue?
 
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Old 02-28-07, 10:44 AM
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check the limit switches, could be causing this
 
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Old 02-28-07, 11:01 AM
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Limit switch location?

Where would I find the limit switch? In the control panel? When I locate the limit switch, what am I looking to do?

Why would the stop-start issue only appear when the t-stat starts the furnace on it's own as opposed to me turning up the furnace?
 
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Old 02-28-07, 11:41 AM
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there will be at least 2... one turns on the fan probably close to the lower part of the fire box, (this one is probably causing the problem) as the fire box gets hot it turns the fan on.. the 2nd is a safety if the fan does not come on it shuts off the gas valve (no flame)
 
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Old 02-28-07, 12:11 PM
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Limit Switch

When I locate the limit switch, what am I looking to do? Is there a setting on them to turn up or down? What will tell me that the limit switch is causing an issue?

Thanks
 
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Old 02-28-07, 04:16 PM
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Clicks on & off

If it runs normally when you manually turn up the thermostat, I think there is a thermostat problem. Most non digital thermostats have a small pointer which points to a scale with numbers on it. This is the heat anticipator. Try adjusting to a higher number. If it is currently set on .4 move it up to .6 or .8.
 
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Old 02-28-07, 04:47 PM
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Grady is most likely right.

What kind of thermostat do you currently have? Has it been changed out from some other kind recently? Is your thermostat by a heat register, stove or any heat source?
 
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Old 03-01-07, 05:40 AM
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Talking Issue resolved!

Thanks for the great ideas guys! The issue turned out to be something that was not being caused by the furnace or t-stat. I am getting power surges into the trailer, thus, why the furnace was kicking in and out randomly. They surges were only noticeable yesterday, as it was shutting down appliances, and surgin lights in the place.

An electrician is supposed to come out today and see what is going on.

Thanks for the help, thought I was losing my mind with the furnace!
 
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Old 03-01-07, 03:44 PM
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Electrical Problem

At least you found out it was affecting more than just the furnace. For some reason mobile homes are more subject to this sort of thing than houses. Hope the electrician was able to fix you up.
 
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Old 03-01-07, 07:39 PM
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Issue continues

Well, the electrician came out and fixed the issue, but I am still getting random furnace restarts after the furance has been running.

Furnace ignites, blower comes on after a certain temp is met, furnace runs, then I get random restarts of the furnace.

I have had the photocell and ignition recently replaced. Seems these issues coincided with the power surges. Something is telling the furnace to stop then restart immediately. Could a limit switch been affected by power surges? I am guessing so.
 
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Old 03-01-07, 07:48 PM
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Random Restarts

Does the fan continue to run or does the entire furnace shut down? Make & model of the furnace might help. I work on a lot of moblie home furnaces & each make has its own set of problems. Since you mention photocell, I have to presume this furnace is oil fired, correct?
 
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Old 03-01-07, 08:22 PM
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Yes. The furnace is oil fired, spark ignition. As well, the fan continues to run and the furnace lights again within 1-2 seconds.

The furnace is a Beckett AF9 MSHA-066AAFO-01.

Sometimes the furnace will run with no issues, other times, the furance will restart 3 times in a row.
 
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Old 03-01-07, 08:25 PM
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would this model have a flame sensor? If so, where might I locate it? Would it be a thermostat issue? Seems like something is telling the furnace or thermostat that it has reached it desired temp and is shutting it down, only to decide that was wrong. Almost like someone is switching the main power switch off and on to the furnace.
 
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Old 03-02-07, 03:10 PM
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Msha

This furnace is either a Miller or an Intertherm (same thing) with a Beckett burner. There could be any number of things causing the burner to drop out but the flame sensor is not one of them. If it only acts up on a normal call for heat but not when you manually turn up the thermostat, I still say the problem is in the thermostat.
 
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Old 03-03-07, 12:29 PM
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I replaced the olf Intertherm t-stat with a Nova programmable digital thermostat, but same issues are occurring, so I can now rule out the t-stat being the prob.

I had major power surges here, I am guessing something could of happened during that time to any number of parts on the furnace. Weird that it does not trip out my system. Just keeps refiring.

Any other ideas? And yes, it is an intertherm with a RW Beckett burner.
 
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Old 03-03-07, 02:40 PM
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Bad wire-nutting of thermostat wires down by furnace or bad connection/corrosion of thermostat wires at furnace?

Bad relay parts where the points/springs are going bad inside?
 
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Old 03-03-07, 03:00 PM
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Found another post on here where someone was having the exact same problem with their furnace, described it to a tee, of the symptons I was having. There issue was the Honeywell primary. They replaced it and all was well. That was my next place to look. Will try to rewire and possibly replace. I think this may be causing the problems. Thing is, I just had this part replaced less than 2 months ago! Thinking the power surges through something off with the primary.
 
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Old 03-03-07, 07:15 PM
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Primary control

A crude but surprisingly effective test of the primary is: While the burner is running use a screwdriver & rap the primary firmly in several places on top & along the side with the screwdriver handle. If the burner stops (may or may not come back on by itself), the relay in the primary is bad & would require replacement of the primary.
 
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Old 03-04-07, 06:16 AM
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Did the rapping on the primary, did not cause it to shut down. Now I may be leaning towards an ignition problem. Seems to be starting and stopping on i's own, and now, after it reaches the set temp on the t-stat, the furnace shuts down, but comes back on shortly after and runs above the t-stat temp.
 
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Old 03-04-07, 09:56 AM
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Ignition

An igniton problem will not cause the entire burner to shut down unless the flame fails to light. If that were the case, you would have to push the red reset button on the primary. All new equipment shuts down the igniton after the flame is established.
Instead of thowing parts (money) at this thing, why not call a local professional? I understand you will have to pay for a service call & their mark up on any parts used but in the long run it would probably be cheaper.
 
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Old 03-04-07, 11:27 AM
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Pretty much going to have to call a professional in. I am at a loss as to what could be causing the random behaviour!
 
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Old 03-04-07, 11:50 AM
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gfraser

As a tech myself, I know how frustrating it can be to find an intermittent problem. Hopefully the furnace will act up when the servicer is there. Like anything else, furnaces are hard to "fix" when they are running as they should. Please post back with the results so others can learn.
 
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Old 03-04-07, 01:20 PM
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Originally Posted by gfraser View Post
I replaced the olf Intertherm t-stat with a Nova programmable digital thermostat, but same issues are occurring, so I can now rule out the t-stat being the prob.
Not necessarily. That conclusion is bad science without tests. You don't know if you have hot air currents tripping on and off a sensitive set stat.

You said it all in a first post when you said when you manually turn it up, it never does it. Only when the thermostat is left alone to try to come on by itself.

When a stat comes on by itself it is in a delicate balancing act of being on and off at the same time due to perhaps 1/2 - 3 degrees of separation depending on the sensitivity setting.

In an older trailer, in particular ones that had 50-60 amp buss fuses, I have seen weird power shifts in trailers that lose one leg of it's 120 volt power. You can turn on the oven and certain lights go orange. But even if that was your original problem the electrician fixed, your current issue is not related, it does not appear.

I'd rule out first, before anything else, that your thermostat is not coming on and off by volt testing during the run operation.
 
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Old 03-06-07, 04:37 AM
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Unhappy

Hi folks,
Thanks for all the great replies! Got a tech out today to take a look at the furnace. Turns out my primary was causing the issue. Sparks actually starting coming from the sucker. Primary would work, but very intermittenly, thus, we think the relay was damaged in it.

Now, onto a milder issue. I recently bought a NOMA 5-1-1 digital thermostat for my Intertherm furnace. The issue I am having is that when the heat kicks in and gets to the desired temp it will shutdown, only to keep cycling every 10 mins after that. Cycling way, way too much. My old intertherm coil thermostat had a heat anticipator setting on it, which should be set at .6. This new, digital thermostat does not have this option. Could this be the cause, and if so, am I out of luck in wanting to use the new thermostat? I have since shut cycling off, so it will heat when the temp drops below .5 degress from the set temp, and shut off when it gets .5 degress above the current temp. Hope this helps, becoming very frustrated with the home heating system!
 
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Old 03-06-07, 03:41 PM
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Noma thermostat

I just did a search for noma thermostats & could find nothing other than a lot of people with problems with them. I suggest canning it & getting either a White-Rodgers or Honeywell. It seems that NOMA is the bargain basement thermostat.
I'm surprised that the old screwdriver test didn't pick up on the bad primary.
 
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Old 03-06-07, 05:01 PM
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Wink

I changed the Noma thermostat to disable the cycles, as I did not like the furnace coming on and off so often. Now, it is is set to come on and off with a .5 differential. So, if my temp is set to 20 and the temp falls to 19.5, furnace kicks in, warms up to 20.5 and shuts down. Lot less cycles and is working as it should!

I did not like the furnace cycling on every 10 mins, or 6 cycles per hour. Seems like that provides a lot of wear and tear on your furnace. Maybe I am wrong and this provides no more wear and tear than is usual?
 
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Old 03-06-07, 05:44 PM
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Thermostat settings

Holding the temperature +/- 1/2 degree is pretty tight temperature control, especially in a mobile home. If you can set the thermostat for +/- 1 you will see even less cycling.
 
 

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