We have a 21 yr. old Carrier gas furnace and I just changed the air filters. When I put the cover back on, even though the thermostat was turned to off, the fan started. I even disconnected the thermostat, but the fan kept going. It runs 24/7. When I finally turned the thermostat to "auto", the heat came on when it was supposed to, but once it was done heating, the fan stayed on. How do I get it to stop?

It hard to say with out knowing the age of the system. If it's a newer system you may have a bad control board if it's a real old system you may have a bad fan limit control. To rule out the thermostat or thermostat wire you will need to check for 24v at the unit from G to C if you have 24v it's a bad T-stat or wires touching together. If you don't have 24v that rules out the thermostat and thermostat wire. If it was a open limit the blower would run but your heat would not. Your heat still works so that rules that out.

Sorry, T-Top. Our unit is 21 yrs. Old.
Even though the fan continued to run after disconnecting all the wires from it, that could still be the problem? We've already replaced the original thermostat.

Could be a tripped overheat limit control. When this control activates it tells the circuit board to keep the fan running.

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Originally Posted by tleahy1

Sorry, T-Top. Our unit is 21 yrs. old.
Even though the fan continued to run after disconnecting all the wires from it, that could still be the problem? We've already replaced the original thermostat.

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Sounds like you have a fan/limit control stuck. Its quite common with that old of a system and a easy fix if your handy with tools and comfortable around electricity.

On a furnace that old, you should be able to replace the existing fan limit with a honewell fan limit control. Do you see a box with a white or black knob coming out of it? Push or pull the knob and see if the blower doesn't shut off. Make sure the thermostat is in the off position while doing this. Let me know if you see this knob. There are a lot of different limits out there, I should be able to walk you through this.

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Originally Posted by T-Top

Sounds like you have a fan/limit control stuck. Its quite common with that old of a system and a easy fix if your handy with tools and comfortable around electricity.

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Thanks, T-Top. I can handle some tools and have no problem with the electric. In fact, I've already shut off the furnace at the panel box.

How would you suggest I proceed?

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Originally Posted by mygirlsdad77

On a furnace that old, you should be able to replace the existing fan limit with a honewell fan limit control. do you see a box with a white or black knob coming out of it? push or pull the knob and see if the blower doesnt shut off. Make sure the thermostat is in the off position while doing this. let me know if you see this knob. there are a lot of different limits out there, i should be able to walk you through this.

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Thanks for your response, MyGirlsDad. I looked at the unit and the only "white/black knob" I see is the white pop out button that turns off the fan if you take the panel off the furnace. When pushed in, the fan goes on, but when it's out, the fan is off. Is that the one you're referring to? That one works.

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Originally Posted by hvac1000

Could be a tripped overheat limit control. When this control activates it tells the circuit board to keep the fan running.

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Thanks HVAC1000. How would I be able to tell if that's the problem?

That will take some HVAC knowledge and a meter to check.
Start by looking on the inside of the blower door for a wiring diagram and also POST your model number for your unit.

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Originally Posted by hvac1000

That will take some HVAC knowledge and a meter to check.
Start by looking on the inside of the blower door for a wiring diagram and also POST your model number for your unit.

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It's model #58DRO75. Unfortunately, the Carrier website doesn't have a copy of our manual and neither do I.

I don't really have HVAC knowledge, nor do I have a meter. If this is something I can't fix myself and need to contact a Carrier repairman, so be it.

If this is something I can't fix myself and need to contact a Carrier repairman, so be it.

So be it.

It could be the relay on the circuit board BUT it may not and without knowledge of testing and tools you might be tossing your $$$ away.


ICM 271 Control Board
Replaces HH84AA020, HH84AA010,HH84AA011, HH84AA012,
HH84AA013, 58GS302075354, CESO110017,
CESO110018, 302075-302, 302075-303, 302075-304, 302075-352,
302075-354, P771-7002, P771-7001,
Robertshaw 695-100
http://www.myhvacparts.com/Catalogue..._Co2_small.gif
Click to enlarge pic
This board works in Carrier, Bryant, PayneDay and Night Furnaces with the factorynumbers listed above. Bryant 394 GAW SIand 394 GAD Model Furnaces. 396GAW, 58GP, 58DP, 58DR, 394GAD, 396GAY, 396GAZ, 394AAD, 58GS, 394GAW, 396GAD,SIZE394JAZ , 396JO, 396JAW

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Originally Posted by tleahy1

Thanks for your response, MyGirlsDad. I looked at the unit and the only "white/black knob" I see is the white pop out button that turns off the fan if you take the panel off the furnace. When pushed in, the fan goes on, but when it's out, the fan is off. Is that the one you're referring to? That one works.

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That is just the blower compartment safety switch. It kills power to the whole furnace.
Is there any way you could take a pic of the inside of furnace.

In calling around. Looks like it's going to cost us at least $500 to get our furnace fixed. One of the questions raised was the age of our furnace. One of the companies suggested the avg. life of a furnace is 15-20 years, which is where we are. Would it make more sense to replace it, in other words, should we expect add'l problems if we just fix our present one?

If we go new, what brand do you all recommend?
Thanks!

Quote:

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Originally Posted by hvac1000

If this is something I can't fix myself and need to contact a Carrier repairman, so be it.

So be it.

It could be the relay on the circuit board BUT it may not and without knowledge of testing and tools you might be tossing your $$$ away.


ICM 271 Control Board
Replaces HH84AA020, HH84AA010,HH84AA011, HH84AA012,
HH84AA013, 58GS302075354, CESO110017,
CESO110018, 302075-302, 302075-303, 302075-304, 302075-352,
302075-354, P771-7002, P771-7001,
Robertshaw 695-100
http://www.myhvacparts.com/Catalogue..._Co2_small.gif
Click to enlarge pic
This board works in Carrier, Bryant, PayneDay and Night Furnaces with the factorynumbers listed above. Bryant 394 GAW SIand 394 GAD Model Furnaces. 396GAW, 58GP, 58DP, 58DR, 394GAD, 396GAY, 396GAZ, 394AAD, 58GS, 394GAW, 396GAD,SIZE394JAZ , 396JO, 396JAW

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In calling around. Looks like it's going to cost us at least $500 to get our furnace fixed. One of the questions raised was the age of our furnace. One of the companies suggested the avg. life of a furnace is 15-20 years, which is where we are. Would it make more sense to replace it, in other words, should we expect add'l problems if we just fix our present one?

If we go new, what brand do you all recommend?
Thanks!

All brand are just about created equal BUT the big factor is how well the new equipment will be installed.

Goodman is the best bang for the $$ and they have a great 10 year factory warranty. Nturally Carrier,Trane, and others are good as well but the install is the most important. I have seen expensive equipment turned to junk by a bad install and I have seen cheaper equipment last a long time just because it was installed correctly.

Quote:

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Originally Posted by hvac1000

All brand are just about created equal BUT the big factor is how well the new equipment will be installed.

Goodman is the best bang for the $$ and they have a great 10 year factory warrenty. Nturally Carrier,Trane, and others are good as well but the install is the most important. I have seen expensive equipment turned to junk by a bad install and I have seen cheaper equipment last a long time just because it was installed correctly.

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Thanks, HVAC1000. Then I guess that takes me to my next question... how do I choose a good installer?

Also, you didn't answer my question about replacement. Is this a good idea at this point, or can I get another 5 yrs. Out of my present system?

21 years is a good amount of time for your present furnace. The newer units are much more efficient so you will save on your utility bill also.

Finding a good installer could prove to be difficult.

Start by getting at least 3 estimates and make sure they compare apples to apples if you know what I mean.

Then check with trusted neighbors/family members for referral

Then call the BBB to see how many complaints have been filed.

I would look seriously at replacement, if you can afford it.
I would recommend goodman, or rheem(ruud). Both have good efficiency, and are simple to work on. I lean toward goodman. Hvac1000 is correct, most new furnaces are pretty much the same, but there are still some out there that I think tend to overcomplicate, which cost more.
As far as installers, word of mouth is your best bet. Just make sure that they give you at least a one year labor warranty beyond the manufacturers equiptment warranty, and you should be just fine.

Quote:

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Originally Posted by hvac1000

21 years is a good amount of time for your present furnace. The newer units are much more efficient so you will save on your utility bill also.

Finding a good installer could prove to be difficult.

Start by getting at least 3 estimates and make sure they compair apples to apples if you know what I mean.

Then check with trusted neighbors/family members for referral

Then call the BBB to see how many complaints have been filed.

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I'm being quoted on single speed and 2 speed units. What's the straight scoop? Which is better and why? One place quoted me $300 more for the 2 speed, while another quoted me $1,100 more. Why?