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M Oglesby
M Oglesby, HVAC Technician
Category: HVAC
Satisfied Customers: 2038
Experience:  Universally Certified HVACR Technician
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i have an ameristar furnace and the red indicator light is

This answer was rated:

i have an ameristar furnace and the red indicator light is blinking 4 times. there is only cold air blowing out of the vents and I've turned off all power to see if it resets. No success. Anything I may have missed?

M Oglesby :

This sounds like a open limit switch.

M Oglesby :

Locate the Main Limit switch.

M Oglesby :

It is a rectangular or square looking device that has two wires attached to it and is about the size of a credit card. It is usually located inside the furnace cabinet on the back panel wall behind the gas valve.

M Oglesby :

Locate it and let me know when you find it.

Customer:

Oh my I'm a mom and not sure where to look first. Are there pictures by chance?

Customer:

be right back

M Oglesby :

You can probably find one at you tube. Just search for a Main Limit Switch for a natural gas furnace.

Customer:

I think I found it. It's tan in color with two wires on it. The wires are yellow and the left looks like it has an orange clip of some sort. Could this be it? About the size of a CC

M Oglesby :

That is it.

Customer:

:)

M Oglesby :

We will need to bypass it.

M Oglesby :

Are you up for it?

Customer:

in the mean time do I shut off the cold air or anything else first. Me and my kids are freezing.

Customer:

Do I also need special tools?

M Oglesby :

Remove the two wires from the Main limit and attach them together very good metal to metal.

M Oglesby :

You may need needle nose pliers to remove the wires from the Limit switch.

Customer:

I have them I do wired jewelery

Customer:

Do I turn off any power first?

M Oglesby :

How long has the furnace been blowing cold air?

Customer:

Just today probably all day since we have been at work and school

M Oglesby :

Yes cut the power first.

M Oglesby :

There should be a cutoff switch at the furnace that resembles a light switch.

Customer:

Is it the one with the GAS CONTROL SWITCH?

Customer:

Turn the position from ON to OFF?

M Oglesby :

No that is the gas valve.

Customer:

There is also a switch when the bottom door is removed.

M Oglesby :

That will suffice.

M Oglesby :

Just remove the bottom door. That will cut the power.

Customer:

OK I just did. I removed the bottom door.

Customer:

now I must remove those two wires and make them have contact?

M Oglesby :

Correct.

Customer:

Okay let me get my tools and get started. Im sorry to place you on wait.

Customer:

im just removing them and making them contact. I'm not placing back together on one side right?

M Oglesby :

No. Attach them or jumper them together.

Customer:

I cannot simply pull them out. Looks like they are nailed in to the panel. Bent like an L shape. Am I doing it wrong?

M Oglesby :

Are you able to take a picture and attach to this chat?

Customer:

yes give me a sec to get the pic taken

M Oglesby :

ok

Customer:

I cannot seem to upload the picture to you. When I browse I click on OK and thats all it does.

M Oglesby :

I want to make sure you have the right switch.

M Oglesby :

What is written on this switch?

M Oglesby :

Is there something like L200 - 40F ex...?

Customer:

there is a bar code with PO2 and 42272 36T01B3 then also AD845 then L170-30F then C340056PO2

M Oglesby :

That is it.

M Oglesby :

You are going to have to get those wires off.

Customer:

Can I send you the picture somewhere else?

M Oglesby :

If you cant do it, you may have to call a professional out in the morning.

Customer:

Full Size Image
see if this worked as an inserted picture

M Oglesby :

No it did not work but I dont need the picture now. We have verified that this is the correct switch. You just need to get those wires off.

Customer:

okay let me try removing the nails

M Oglesby :

ok

Customer:

I got one off but the orange clip is harder

M Oglesby :

ok

M Oglesby :

It is almost 2:00 am in Atlanta. That is where I am.

Customer:

I am so sorry to have you working this late. it is almost one am for us.

Customer:

I took them both off but the let has the metal inside the plastic casing. How do I make contact?

Customer:

Whats the best aproach?

Customer:

the *LEFT has the metal inside and plastic outside

M Oglesby :

Use a piece of wire or a paper clip to jumper them together.

M Oglesby :

Once they are attached, attempt to turn the heat back on.

M Oglesby :

Let me know if it comes on or not

Customer:

okay brb

M Oglesby :

ok

Customer:

can I use masking tape to hold them together?

M Oglesby :

no

Customer:

Okay M Oglesby. I've shaped wire into a letter H and placed it inside each and connected them. By placing the bottom door back it will start to turn on correct? Will it spark? Is this dangerous? I'm kinda scared now.

Customer:

they are connected and back by the main limit switch panel.

Customer:

Do they need to keep distance from Gas Valve?

M Oglesby :

no

M Oglesby :

turn it on

Customer:

I pressed the switch with a plastic mallet and it turned on the burners YAY!!!!! :) Is it safe to replace the door covers then?

Customer:

Safe to leave it with the piece of wire in it?

Customer:

or did this just jump start it and now I can clip them back to the main limit switch?

M Oglesby :

That means that you will have to replace the main limit switch.

M Oglesby :

It is bad.

M Oglesby :

It is not safe to leave the furnace jumped this way.

M Oglesby :

this is just a troubleshooting test.

Customer:

is that the panel portion or the wire portion?

M Oglesby :

The panel portion

M Oglesby :

I advise you to call a tech out to replace the Main LImit switch for you.

M Oglesby :

Please hit ACCEPT if you are satisfied with this service. Thanks! Bonuses are greatly appreciated!

Customer:

okay. So this is above my knowledge my head. What about tonight? it is dangerous? for the night?

M Oglesby :

I would not advise you to use the furnace in this manner even for the night.

Customer:

Okay Thank you very much for your patience and time and knowledge. God bless you.

M Oglesby :

Thank you!

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