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The Home Smithy
The Home Smithy, Home Appliance Technician
Category: Appliance
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Experience:  30 years repairing appliances
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I have a Rheem RGRA06EMAES condensing gas furnace. It ...

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I have a Rheem RGRA06EMAES condensing gas furnace. It wil not light and is giving a 3 blink error message that indicates "limit switch is open." Is there anything I can do to get it running again?

Hi rohlway;

What you need to do is look under the units cover and see if you can find a part that has two wires going to it that has a red button. If you find it, push the button, and you should be back in business. If there is not one then you will need to know how to read schematics. There is a schematic of the electrical wiring on the inside of one of the cover panels. All units are required to have one. From that you can trace the unit down using the wires, and color codes.

If you do not know how to read schematics then you can take a picture of the diagram, and I can tell you how to upload it to our servers. I can then trace out the appropriate wires, and tell you how to trace the item down. A picture of the unit with the covers off would be very helpfull.

Please advise how you wish to continue.

Awaiting your reply; The Home Smithy

Customer: replied 9 years ago.
Let me check see if I can find the physical switch. Otherwise I do have the manual which has a schematic. I'll get back to you as soon as I've checked.

ok great


Customer: replied 9 years ago.
Reply to The Home Smithy's Post: I think I found the limit control switches (1 main [LC] and 3 others [MRLC]) but I can find no reset button, red or otherwise, anywhere. The schematic in the manual is dwg # XXXXX rev. 02. The schematic stuck to the door is the same #, but rev. 04. They look identical when it comes to the limit switches--and everything else I can find. I can easily scan the schematic in the manual; uploading a digital photo of rev. 4 is a little more complicated. What do you suggest?

If you can scan the one in the book and save it as a .jpg you can upload it here to our servers.

here is how you upload them-

At the top of your reply box is a icon that looks like a tree. It is two to the right of the smiley.

Click on the icon. It will bring up a box.

Click on browse. Another box will appear.

Click on browse again in that box.

Navigate to the place in your computer where the picture is. Select it, and then in the second box click on upload.

The second box will disapear.

In the first box click on insert.

This will upload your picture, and you should see it displayed in your reply box.

Repeat the process to upload another picture.

Customer: replied 9 years ago.
Reply to The Home Smithy's Post: I'll scan and upload the picture.
Customer: replied 9 years ago.
ok checking it now.

Ok I have indicated the wires you need to trace down to find the limit switch. Unfortunatly yours is not resetable, and if it is not working properly will need to be changed. The good news is you can get one that you can reset, and install it in place of the non resetting one.

fyi MLRS is short for Manual Limit Reset Switch they are optional on your unit (the big X)


If this answer satisfies your question please click on the accept button. If it does not, please tell me so. You are not expected to accept any answer that you are not happy with. I do expect you to let me know if you are not satisfied, and what I can do to put a smile on your face.

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Best regards; The Home Smithy
After you have accepted it is important that you leave positive feedback.

The Home Smithy and 3 other Appliance Specialists are ready to help you
Customer: replied 9 years ago.
Thanks for your help. I definitely will accept and leave positive feedback. A couple of final questions. (1) If, as it appears, I have 3 MRLC's as well as 1 LC, would you recommend replacing all 4--or just the LC? (2) any tips about where to find parts? (I can just Google.) (3) Since they all are attached to a controller board, might I have to replace the whole thing?

Ok You do not have 4 of them just the one. If you had 4 you would have found 3 reset buttons. One on each of the MRLCs. As i said before MRLC stands for manual reset limit switch. These have red buttons to reset them manualy with. They are not attached to the board, they are at the opposite end of the wireing harness.

nd you should be able to get them at any heating and airconditioning supplier. Just look in your local yellow pages under heating and A/C.

Let me know if you have any more questions.

Customer: replied 9 years ago.
Great. Thanks. I already accepted the answser and entered positive feedback.

Thank you for both. Laughing

Best regards; The Home Smithy

Customer: replied 9 years ago.
I couldn't find the switch--which may be soldered to the circuit board, which would have to be removed, so I may be in over my head. I attach a couple of pictures in case you can spot something that I didn't--like a switch not on the board that I could easily replace. But I don't see anything like that with a two red or r/w wires. I did learn a thing or two and will ask them to use a replacement that has a reset button, as you suggested. So thanks again. graphicgraphicgraphic
Ok checking now. Can you get me a closer shot? Square on, please about 1 1/2' away would be about right.
Customer: replied 9 years ago.
Reply to The Home Smithy's Post: I'm at work. I'll see what I can do when I get home this evening.

No problem, Here is a hybred of the schematic ans the photo. I cant tell if that is a 9 pin or not but I think that is the connector. I highlighted the wires that come out of it with the proper colors. All you have to do is find a connector that matches the wire colors as indicated and you can trace them from there.

BTW the limit switch is not on the circuit board. It will be behind the cover on the upper half of the unit on the fire box.


Customer: replied 9 years ago.
Cool. I think it's a 9 pin too. If it is, I remove the cover to the top compartment, follow the wires up through the grommet to find the switch. (If that's correct, no need to reply.) I'll take a look when I get home and get back to you.

Yes that is correct.

And if I do not reply. Your question remains in my "waiting for experts reply" list. That doesnt look good to the boss ya know.

Customer: replied 9 years ago.
OK. I found the thing. Its base is the square to the left of the valve(?). The little guy above it and toward the center with the two red wires might be a manual reset limit switch, but I couldn't see any manual reset on it. One guy quoted me $15 on an OEM replacement for the main limit switch; another said a replacement would be $150. Rather than risk having the heat out for several more days I'm keeping my service appointment for today and letting the HVAC service company fix it and correct the problem that caused it to go out. Still, I'd be interesed in any final comments. But this has been very instructive. Thanks again. (I'll also do the accept and feedback routine again.)graphic
Customer: replied 9 years ago.
Update: The service guy said the switch is resettable, by hand. Some kind of nipple on it that has to be pushed in when it opens up. Maybe have to remove the switch to get at it. For now, he just reset it. Also said that I could indeed get a replacement for c. $15. He thinks the cause of the problem is small ductwork and highly restrictive (anti-allergen) filters.

yup I would have to agre with him. As for a nipple there isnt one on the square one but your probably right about the one at the top. you can easily tell just look for a common wire inbetween them. They will be wired in series as in the electrical diagram. You dont necessarily have to have all 3 MRLSs' you may only have the one. Or you could have two.

As for the restrictive ducting. If it is in fact restricting the flow then I would have it checked for possibly being undersized, and then go after the installers to correct it. But it could just be the filters also. Clean air is a good thing. I personally have never put much stock in the superscrubber filters myself. I figure that if you clean the things your body uses too much it wont be able to fight the nasties when they do attack.

You have already accepted, so you dont have to again, Bonuses are welcome though.

Best regards; The Home Smithy

The Home Smithy and 3 other Appliance Specialists are ready to help you
Customer: replied 9 years ago.
Thanks again. I attempted to add a bonus of $10, and think I succeeded.

Yes it did. Thank you! Laughing