# My Carrier high efficiency furnace



## how (Feb 26, 2011)

HeyWxia
Start up a new thread for your furnace as it will confuse everyone if you don't.


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## how (Feb 26, 2011)

Hey wxia
Are you saying that your diagnostic led doesn't blink a code after a lockout or that you can find the led light? If you can't find it, look for it on an electronic board. If the board is only accessed behind a panel that has a door switch, then tape that door switch shut so you can access that led light code the next time the furnace locks out without cutting off it's power.
In the mean time, un screwing & cleaning the flame sensor with steel wool it the easiest and most possible common fix to first try.


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## Houston204 (Oct 18, 2009)

Carrier didn't have the LED in that mid 1980's furnace.

The edge pin connector labeled 10B1 can corrode inside and turn green (instead of the normal silver). The pc board connection to it can as well.

I've had a tech clean the inside with some flattened steel wool, then blow it out with compressed nitrogen and get one back on line before.

Any steel wool left behind could cause problems.


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## Tator1076 (Dec 22, 2009)

So you have nothing when it comes back on?


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## Tator1076 (Dec 22, 2009)

Is the fan running, is it trying to spark? Is this l.p or N.G


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## wxia (Feb 12, 2012)

Once I get it restarted, it often runs normal for days before it does it again. I will do what is suggested by Houston 204 and let you know if that works.


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## Tator1076 (Dec 22, 2009)

Sure the lockout module is maybe going out. It lock out the unit for 3 hours before restart


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## Tator1076 (Dec 22, 2009)

Is that for l.p. for vapor lock out on low tank or low tank pressure?


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## wxia (Feb 12, 2012)

I do not know what is "l.p. for vapor lock out on low tank or low tank pressure?" Every time when I notice the furnace was not running and the temperature did not rise to the thermostat setting, I restart the furnace by switch the power off and on. It started working right away and often continues for days.


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## Tator1076 (Dec 22, 2009)

L.p. is propane gas. You on l.p.?


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## wxia (Feb 12, 2012)

No, mine uses natural gas.


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## wxia (Feb 12, 2012)

I have cleaned the flame sensor and checked all connectors on the board that I can see. The connectors all look fine and relatively tight. I do not have much confidence if these are related to the problem. In the next few days I will see if the problem goes away.


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## dosy777 (Feb 6, 2012)

wxia said:


> I have cleaned the flame sensor and checked all connectors on the board that I can see. The connectors all look fine and relatively tight. I do not have much confidence if these are related to the problem. In the next few days I will see if the problem goes away.


3 common problems with those units, 1 st off the secondary heat exchangers are failing at a pretty high rate, check that FIRST before you sink any money into it. The other two things are the 3 wire pilot, and the gas valve. BTW unless it is one of the very last sx's that was made it may not have a true flame sensor, the last year that carrier made them was the first year that they started using a flame sensor and a ignitor.......would it be possible for you to post a picture of your furnace with the doors off?


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## hvac5646 (May 1, 2011)

wxia said:


> I have cleaned the flame sensor and checked all connectors on the board that I can see. The connectors all look fine and relatively tight. I do not have much confidence if these are related to the problem. In the next few days I will see if the problem goes away.


no sensor on that model. had a bi-metal pilot.


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## wxia (Feb 12, 2012)

I will check on them. By the way, when it failed to restart last time, I was able to get it restarted from the thermostat by switching to "fan only" and then back to "heat". That got the fan started first, then shut (when switched back to "heat", then the heat cycle started. Therefore, it appears after the furnace fails to restart, I could trick it to restart by either switching the power off and on or by switching the thermostat from "heat" to "Fan only" and back. I just do not understand where the problem is.


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## wxia (Feb 12, 2012)

I have attached photos of the furnace from outside to inside. It has a hot surface type ignitor which appears to work well.


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## dosy777 (Feb 6, 2012)

I would defiantly be looking at the secondary heat exchanger..........and also as i suspected, you DO have a flame sensor, as you stated.


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## wxia (Feb 12, 2012)

How can I tell if the secondary heat exchanger has a problem?


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## hvac benny (Dec 29, 2009)

Those are some poor looking gas lines. No drip legs and flex connectors to the furnace and water heater. If the installers didn't install drip legs (required by code and used to prevent foreign material from getting into your gas valve) who knows if they commissioned (temp rise, gas pressure, clocking, etc.) the furnace at all, which would lead to a shortened life span of the furnace.


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## hvac5646 (May 1, 2011)

This diagram does not match the furnace shown above.. Made me think it had no flame sensor...looks like we has wrong.



Houston204 said:


>


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## dosy777 (Feb 6, 2012)

wxia said:


> How can I tell if the secondary heat exchanger has a problem?


From a assisted visual view, in your case I would remove the evaporator coil access door, then remove the panel to access the under side of the evaporator coil. From that point using a visual aide (a camera such as a sneaky snake) looking down past the primary at the secondary. 

What you are looking for is a white crusty build up on the secondary, that would be a sure sign that the secondary heat exchanger is bad. you can also remove the blower and look up, but in your case you have a hell of a lot going on in the blower area, and I noticed that you also have a 5 ton drive (indicated by the dual blower housings).

Around here I would say that every 9 out of 10 that we look at have a bad heat exchanger. If you do find that it is bad I would call carrier, or a carrier dealer, If your the original home owner, it may still be covered for the parts anyway.Any time we change them out we always change primary and secondary, carrier was always OK with that and was easy to work with.


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## dosy777 (Feb 6, 2012)

after searching the internet I was able to find a picture of a bad carrier heat exchanger......here it is


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## Tator1076 (Dec 22, 2009)

Look at the door switch is tape up and black marks behind it. Is that been tape the whole time?


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## Houston204 (Oct 18, 2009)

http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/58d,s-8sm.pdf

Looks like the 1992 model 58SXC.


It still has an edge pin connection on top. Were you able to remove the connector and inspect for corrosion?


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## hvac5646 (May 1, 2011)

dosy777 said:


> I would defiantly be looking at the secondary heat exchanger..........and also as i suspected, you DO have a flame sensor, as you stated.



Where do you see a flame sensor?


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## Houston204 (Oct 18, 2009)

It appears that the 92 model had a flame sensor.

From the manual posted above...


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## how (Feb 26, 2011)

I'm still trying to get my head around the enclosed burner compartment of a 90% that uses bi metal controls. They seem too slow a choice to meet the challenge.


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## hvac5646 (May 1, 2011)

how said:


> I'm still trying to get my head around the enclosed burner compartment of a 90% that uses bi metal controls. They seem too slow a choice to meet the challenge.


They worked gooder than hell and were well ventilated and kept back from the main burner.


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## wxia (Feb 12, 2012)

hvac 5646: The flame sensor is in the flame compartment at the top. It is in pretty good condition based on my visual inspection.

hvac benny: The gas line does have a flexible connection to the far right of the furnace, but it does not have a drip section as you mentioned. I hope this did not cause the problem I am trying to deal with. 

Houston204: I removed the edge pin connection, cleaned it with sand paper, and put it back. The connection looks fine or normal (no obvious corrosion noticed).

Tator1067: I taped up the door switch on suspicion of it being the problem. I accidentally had the hot wire touching the metal case resulting in the black mark (and tripping the circut breaker).

I will try to figure out how to inspect the secondary heat exchanger. This is going to be a difficult job.


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## hvac benny (Dec 29, 2009)

wxia said:


> The gas line does have a flexible connection to the far right of the furnace, but it does not have a drip section as you mentioned. I hope this did not cause the problem I am trying to deal with.


Sorry wxia, I wasn't very clear. The flex lines aren't required, but are fine to use, I just don't like them. In my opinion, connecting them to a fixed appliance is the lazy way. No biggy. As for the drip legs, their absence wouldn't cause the problems you're experiencing.


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## dosy777 (Feb 6, 2012)

wxia said:


> hvac 5646: The flame sensor is in the flame compartment at the top. It is in pretty good condition based on my visual inspection.
> 
> hvac benny: The gas line does have a flexible connection to the far right of the furnace, but it does not have a drip section as you mentioned. I hope this did not cause the problem I am trying to deal with.
> 
> ...


 I could have the entire heat exchanger on the flor in about 20 minutes......to me its an easy one to change.


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## hvac5646 (May 1, 2011)

wxia said:


> hvac 5646: The flame sensor is in the flame compartment at the top. It is in pretty good condition based on my visual inspection.


Yeah, I finally got the model straight in my memory. YOURS does have a flame sensor.

The first diagram Houston posted did not ...it showed the model but the diagram showed a bi-metal pilot assembly instead of the flame sensor.

Problem was Hpuston's first diagram didn't show the full model number and I accepted it as your model.


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## hvac5646 (May 1, 2011)

hvac benny said:


> Sorry wxia, I wasn't very clear. The flex lines aren't required, but are fine to use, I just don't like them. In my opinion, connecting them to a fixed appliance is the lazy way. No biggy. As for the drip legs, their absence wouldn't cause the problems you're experiencing.


That is just the way things are done in his neck of the woods. We use stainless steel connectors here also. But we run them from the black pipe drop and drip to the gas control.


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## hvac5646 (May 1, 2011)

*Any body notice the condensate stain on the board????*


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## wxia (Feb 12, 2012)

hvac5646: The "stain" at upper part of the board is not stain or condensate but dust accumulation due to a gap at the edge pin connector and suction from the blower.


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## Houston204 (Oct 18, 2009)

None of my posts show the entire model number because it was never posted.

All of the other 58SX manuals (58SXA, 58SXB) show a bimetal flame sensor.

I did see that grey area but figured it was dirt.
I wonder if this much dust can cause an intermittant problem.


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## hvac5646 (May 1, 2011)

wxia said:


> hvac5646: The "stain" at upper part of the board is not stain or condensate but dust accumulation due to a gap at the edge pin connector and suction from the blower.


Ok..but it looks like a stain to me.




Danged low resolution monitor...that's what i get for buying a $100 monitor.


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## wxia (Feb 12, 2012)

Dosy777: I have not figured out an easy way to inspect the heat exchanger. I opened the front of the evaporator and the evaporator coil blocks any view down. I may need to access from the side. On the parts warranty, I am not the original owner and the furnace is 20 years old. A reference mentioned early appear to indicate I would not get any warranty. But why would a bad secondary heat exchanger cause occational time out or no-restart, particuarly I could manually restart it with a flip of the power switch?


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## dosy777 (Feb 6, 2012)

wxia said:


> Dosy777: I have not figured out an easy way to inspect the heat exchanger. I opened the front of the evaporator and the evaporator coil blocks any view down. I may need to access from the side. On the parts warranty, I am not the original owner and the furnace is 20 years old. A reference mentioned early appear to indicate I would not get any warranty. But why would a bad secondary heat exchanger cause occational time out or no-restart, particuarly I could manually restart it with a flip of the power switch?


 The rust and corrosion is causing a back up or a slow drain and removal of condensate from the secondary heat exchanger, this is monitored by the pressure switches, and they are tied into the ignition control.


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## wxia (Feb 12, 2012)

I have not had time to open the evaporator area to look into the heat exchanger. For the last two mornings in a row I noticed the furnace (my downstairs) was not running in the morning and temporature was about 62 degrees instead of 68 degrees called for. Each time I was able to restart it by switching the thermostat to off and then back right away.


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## hvac5646 (May 1, 2011)

Please start a new thread...and welcome to the site.


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## wxia (Feb 12, 2012)

This is a very good tip for me. Once the box is replaced, please let me know how much the box costs you and where the device is located.


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## wxia (Feb 12, 2012)

hvac5646: I am all for restarting a new thread, however the history would be lost on this particular issue.


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## hvac5646 (May 1, 2011)

That's why we have pros to answer questions.... archives for posters to look up old threads


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## hvac5646 (May 1, 2011)

goodluck.


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## wxia (Feb 12, 2012)

mrwkndr: It looks that you have the exactly the same problem as mine. Let me know how your problem is solved if it is solved.

I looked at my furnace and there is no ease way to open it from the sides (in order to look into the heat exchanger). There are other things in the way.


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## wxia (Feb 12, 2012)

My furnace problem may be temperature sensitive. For the past week, it has not been a problem probably due to a little warmer temperature in my furnace room as our outside temperature has risen to generally above freezing (I am in Salt Lake City, Utah). My furnace (downstairs) does not need to run at night. Does this mean some component of the board or switch locks up at low temperatures but can be re-activiated with a power surge from the flip of the on/off switch?


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## how (Feb 26, 2011)

All borderline parts can be affected by the difference that outside temp presents because it makes the furnace run more often and for longer.

It probably means though that you might be able to instigate a lockout while testing components by turning up the thermostat high enough to mimic the over night colder conditions.

If you can instigate a lock out on your schedule, then you can at least test out one component per lockout..


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## wxia (Feb 12, 2012)

how: Your sugestion is plausible but I doubt it is that simple. In my most recent furnace "lockouts," the temperatures on my first floor were around 62 degrees which was 6 degrees below what the thermostat called for. I do not remeber that the furnace was ever running shortly before I noticed the "lockout." The furnace is located in the basement which would probably be 10 degrees colder than the thermostat's location. That 62 degrees was probably the lowest temperature reached without the furnace heating at night on my first floor (rather than the furnace ran too long before it quit or was locked out). Recently, under a little warmer climate conditions, the furnace have had no problems heating my first floor to 68 degrees and maintaining it at that temperature all day.


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## how (Feb 26, 2011)

Who knows???
People seldom notice an intermitant lockout until they get chilly... which is some time after the furnace locked out and is dependant on how well your home holds in the heat.

If you crank up your heat up 5 degrees above what is normal for you and the furnaces locks out after a while then you have gained an active method for testing components for what was formally a difficult to diagnose intermitant problem.
If the furnace doesn't lock out..then its just onto the next idea.


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## beenthere (Oct 11, 2008)

Restricting condensate drain.


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## wxia (Feb 12, 2012)

Yesterday I cranked up my thermostat by 5 degrees more. The furnace ran for more than two hours with no problems - no lockout!

I looked at the condensate drain and did not see anything abnormal. There is evidence the condensate did drain, although I do not know how much. I am not sure how to tell if the drain is restricted.


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## beenthere (Oct 11, 2008)

Remove trap and wash it out. Also blow out drain line.


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## wxia (Feb 12, 2012)

I removed the hoses from the top of the condensate trap and blew air thru the trap and the hoses separately (with my mouth). There was no restriction.


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## beenthere (Oct 11, 2008)

I wash the traps out with dish soap. Lots of dirt in them. may not be your problem.


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## wxia (Feb 12, 2012)

*Problem solved*

It was the batteries that were low in the thermostat. Once I replaced them it has no more problems. This explains why I had problems often in the cold mornings.


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