# Main Limit or Rollout Switch is Open (Heil)



## heilProblems (Jan 11, 2013)

I have a 10+ year old Heil furnace with a Honeywell SV9541M "Smart Valve" 

The furnace ignites and runs for approximately 4 minutes before the gas is shutoff. The smart valve flashes 4 flashes, indicating according to the manual "Main Limit or Rollout Switch is Open". 

After about 1 minute it starts up once again and seems to complete the heat cycle. 

I've recently replaced all the hoses and cleaned the flame sensor. 

There are 2 rollout switches (the small ones, part number 1013102) and 1 main limit switch (part number 1320367) right in the middle. 

I'm not sure how to tell which is faulty. Any way to tell? 

Also, the smaller switches have a pink dot on them, does this indicate polarity of some kind? 

And how do you "reset" these switches? There's what looks like a button on the back of the smaller ones but nothing on the larger "main" limit switch. The button on the smaller ones doesn't hardly move. Would that have popped out if these switches had been tripped? 

Could this be related to the pressure switch in any way? 

Thanks in advance, this forum has been a huge help to me in the past and I'm hoping to call on your expertise once again.


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## beenthere (Oct 11, 2008)

The roll outs are manual reset. If its completing the cycle without you having to reset them. then its the main limit switch that is opening. Either the blower wheel is too dirty, the A/C coil, or your air filter.

If you have to reset the roll out. Then you may have a bad heat exchanger.


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## heilProblems (Jan 11, 2013)

Thanks for the reply. Does that mean there's basically not enough air moving through the system? I'm trying to guess at what's happening here but it sounds like the switch trips when it gets too hot. 

How would I go about fixing something like this? Should I remove the blower motor and look at that?


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## beenthere (Oct 11, 2008)

Yes, low air flow is the usual problem.

Open the blower panel and you should be able to look into and see if the wheel is dirty. 

If you have central A/C, the evap coil could be dirty and causing this problem.


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## heilProblems (Jan 11, 2013)

I did some disassembly last night and took some photos (see attachments). 

I don't see any dirt anywhere. The filter is brand new. The blower motor has some minor dirt but spins very very freely. I even slid my phone up underneath the blower and took some photos of the heat exchanger and it looks brand new. 

I do think airflow is the problem as I ran the unit with the lower door off, allowing air to flow freely into the blower and it ran the entire heat cycle without problems. 

Any ideas what to look at next? Is my ducting the problem? Is it possible I have a filter in there that doesn't allow enough CFM?


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## beenthere (Oct 11, 2008)

Air filter looks dirty. Also your secondary heat exchanger is dirtier then you think.

Do you have central A/C connected to that furnace. If so, that coil may be dirty and causing the problem.

Are there any supply registers turned off, if so, open them. Are any return grilles closed or blocked off. If so, open them, or move what is blocking them.


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## ben's plumbing (Oct 6, 2011)

yea filter looks dirty ....in fact i really don't like those pleated filters at all...but try running system without filter see if it gos through a proper cycle...ben sr


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## heilProblems (Jan 11, 2013)

The filter is brand new installed this week, the black is actually a Carbon coating to reduce odors. We don't have a problem with odors so maybe I'll try an alternative filter. 

The link to it is here: 

http://www.amazon.com/Filtrete-Redu...61338&sr=8-4&keywords=carbon+air+filter+16x25

The unit does run through a full cycle no problem without the filter. Is there another style of filter you guys recommend? I have a 16"x25"x1" opening.


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## beenthere (Oct 11, 2008)

Just use a general pleated air filter. Nothing higher then a MERV 8.


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## patrick1926 (Jan 1, 2021)

heilProblems said:


> The filter is brand new installed this week, the black is actually a Carbon coating to reduce odors. We don't have a problem with odors so maybe I'll try an alternative filter.
> 
> The link to it is here:
> 
> ...



Where you able to resolve the issue? I have similar problem where heartbeat light flashing constantly and that indicate that it working fine.

But I have very low air flow from duct and i have replaced the filter and inside look good. 

I see that both switch got 140 F when it shuts off. 

Under normal condition we should have continuity on both terminal correct?


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