HVAC Fan Always On


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Old 02-19-08, 09:04 PM
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Question HVAC Fan Always On

Carrier Model 58GP075-2 Series 311 20+ years old

Forced Air; Gas Heat; A/C Single Stage

Carrier Thermostat seems original to the unit. Round dial. Switches: Heat, Off, Cool; Fan On or Fan Auto.

Problem.

1. Fan is always on.
2. If thermostat is set to Heat, Off, or Cool ... Fan always on.
3. If fan is set to Auto, fan stays on even after gas heat has cycled off.
4. When Fan is switched from Auto to ON, Fan goes to High Speed.
5. When Fan is set to Auto, Fan goes to Moderate Speed.
6. Thermostat turns on Gas burners correctly. Gas Heat cycles on and off correctly and keeps temperature per the setting on the thermostat.
7. Four Wires connected to Carrier Thermostat
W - White Wire
Y - Blue Wire
R - Red Wire
G - Green Wire
8. Unit has a wiring schematic taped to access panel.

Before I buy a replacement thermostat, what steps should I take to determine if the problem is with the thermostat or if the problem is elsewhere?

Thanks for your help.

Robert
 
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Old 02-20-08, 02:23 AM
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Disconnect thermostat and see if fan still runs...

My guess would be its not the t-stat. It's the fan and limit control or the fan relay is stuck...the fan relay is the cube like box on the control board in blower capartment.
 
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Old 02-20-08, 02:42 AM
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As old as this unit is, "is a Carrier"... and the guys at Carrier always loved to load their units with electronics

Your unit then has a circuit board. Look there for two terminals called LIM-1 and LIM-2. From terminal LIM-1 a red wire should go and connect to a terminal which is part of a switch called the FUSIBLE LINK. The other terminal of this FL switch connects to one terminal of the LIMIT switch, the other terminal from the limit switch has a brown wire that ends up at terminal LIM-2 back on the board.

So...one of these two switches (or both) is (are) bad. Most likely the FL.

Place a jumper between the two terminals of the FUSIBLE LINK. If the blower stops, the Fusible Link is bad.

If the blower does not stop, continue on...
Remove the previous jumper and place a jumper between the two terminals of the LIMIT. If the blower stops, the Limit is bad

If the blower still does not stop, continue on...
Remover previous jumper and place a jumper between terminals LIM-1 and LIM-2. If the blower stops, both switches (Fusible Link and Limit) are bad.



This should do it.
Good luck!
 
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Old 02-20-08, 04:29 AM
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Thanks. This list is exactly what I wanted. I'll run the tests and let you know what I find out.

I appreciate the time you spend helping people out.

Robert
 
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Old 02-20-08, 10:02 AM
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Both LIMIT & FUSEABLE LINK appear to be good and not the problem.

Test Results. Jumpred switches and also etsted switches with Volt-Ohm Meter.

1. Jumpered goth terminals of LIMIT Switch. Fan still ran. Switch has continuity.

2. Jumpered both sides of FL. Fan still ran. Fuse has continuity.

3. Jumpered LIM-1 and LIM-2. Fan still ran. No Continutiy between LIM-1 & LIM-2 when connectors are reomved.

4. Disconected all wires from thermosat to circuit board. Fan still ran.

There are two relays CFR and HFR (small rectangular boxes) attached to the circuit board. I was not sure if they would disconnect from the circuit board so I did not mess with them.

Not sure if this will help since the fan runs even when all wiers from thermostat are disconnected.

Circuit Board has wires connected from thermostat as follows:
C - Red wire to A/C unit
Y - no wire
GC - Green wire from thermostat
GH - No wire
R - Red wire from thermostat
W - White wire from thermostat

The Blue wire from thermostat is connected to a white wire that goes to A/C along with the Red wire from the C connector on the circuit board.

What else can I try to find the "culprit"?

Thanks.
 
  #6  
Old 02-20-08, 10:05 AM
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Wink

4. Disconected all wires from thermosat to circuit board. Fan still ran.
Then Id say go for the blower relay. Can be on a board.
 
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Old 02-20-08, 11:03 AM
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Pls take a close-up pic of the board...not too far, not too close, and post it.

You indicate that there is nothing connected to the Gh terminal. A jumper should be placed between Gh and R. Did you or someone remove it?

CFR and HFR are, respectively, Cooling Fan Relay and Heating Fan Relay. I don't think they are removable, but a close-up pic will allow me to see so I can tell for sure.

HFR has (internally) a 24V coil and a pair of N.C. contacts. These contacts are the ones that are keeping your blower running non-stop. Why? b/c the jumper between Gh and W is missing.

The transformer's hot leg (24V R-terminal) feeds power to this coil by going first thru the two limits you just tested and then to the R terminal on the board. The jumper between R and Gh will allow the electrical signal to continue on its way to the relay coil of HFR, which in turn will cause the N.C. contacts to open, turning the blower OFF.

So...what will turn the fan back ON when needed on a call for heat? well, terminal W on the board, which gets its juice from terminal W on the thermostat (on a call for heat), feeds the electronic time delay circuit (which is part of the board)...This time-delay control (which is a solid state device) will count 75 seconds after which talks to a triac switch which in turn kills power to the coil of HFR, causing its contact to close once again and voila...the fan is now ON thru the rest of the call for heat period.

Yup! these guys at Carrier certainily like to do things the hard way.

So...put that jumper in place and report back on the forum with the news.
 
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Old 02-20-08, 01:56 PM
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Thanks Ed and pflor.

The Carrier unit I'm working on belongs to a single mom who is a friend of the family. She called and said the fan was running continously.

The wiring is the way I found it. I did not remove a wire from the Gh and W. I'm sure the owner did not remove it. Mystery.

I'll put a jumper between the Gh and W and see what happens. It will be a few days before I can report back.

Let me see if I got this right. If the N.C Contacts in the HFR are closed, the fan is on. When the contacts are open, the fan is on.

The fan runs even when the unit is set to Cool. Does this make any difference?

Also, Ed mentioned a blower relay on the board. Is this a removable component or some kind of soldered component? Can I test it with a Volt/Ohm meter?

BTW, N.C. contacts means normally closed, right?

Thanks.
 
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Old 02-20-08, 01:59 PM
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Correction

Let me see if I got this right. If the N.C Contacts in the HFR are closed, the fan is on. When the contacts are open, the fan is OFF.
 
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Old 02-20-08, 02:20 PM
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If you know where the relay is, one way to test it is to tap it when it's supposed to turn the blower off. If it's stuck, this might un-stick it, and if so you know the relay's bad.

Another possibility is the high temp limit switch is stuck open or closed, due to either overheating or a bad switch. Overheating in turn can be caused by lack of air flow (such as from a clogged filter).

See if there's a manual reset for the high limit.
 
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Old 02-20-08, 02:22 PM
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Originally Posted by GAVolunteer View Post
Thanks Ed and pflor.
Let me see if I got this right. If the N.C Contacts in the HFR are closed, the fan is ON. When the contacts are open, the fan is OFF.
your understanding is correct

Originally Posted by GAVolunteer View Post
The fan runs even when the unit is set to Cool. Does this make any difference?.
On cooling the fan will run, yes, but at a higher speed than heating.

Originally Posted by GAVolunteer View Post
Also, Ed mentioned a blower relay on the board. Is this a removable component or some kind of soldered component? Can I test it with a Volt/Ohm meter?
Very, very unlikely that the relay is removable, but to be sure is that I asked for a close-up picture. No, I do not think you'll have any room to stick the leads of a meter there.

Originally Posted by GAVolunteer View Post
BTW, N.C. contacts means normally closed, right?
correct

...
 
  #12  
Old 02-20-08, 02:25 PM
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Originally Posted by pflor View Post
As old as this unit is, "is a Carrier"... and the guys at Carrier always loved to load their units with electronics

Your unit then has a circuit board. Look there for two terminals called LIM-1 and LIM-2. From terminal LIM-1 a red wire should go and connect to a terminal which is part of a switch called the FUSIBLE LINK. The other terminal of this FL switch connects to one terminal of the LIMIT switch, the other terminal from the limit switch has a brown wire that ends up at terminal LIM-2 back on the board.

So...one of these two switches (or both) is (are) bad. Most likely the FL.

Place a jumper between the two terminals of the FUSIBLE LINK. If the blower stops, the Fusible Link is bad.

If the blower does not stop, continue on...
Remove the previous jumper and place a jumper between the two terminals of the LIMIT. If the blower stops, the Limit is bad

If the blower still does not stop, continue on...
Remover previous jumper and place a jumper between terminals LIM-1 and LIM-2. If the blower stops, both switches (Fusible Link and Limit) are bad.



This should do it.
Good luck!
That won't do it. I think you missed the part of his post that indicated the burners DO come on. Although very nice post.


From what I've read so far it appears to be Heating Fan Relay is stuck in the closed position. Which means a new board.
 
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Old 02-20-08, 02:36 PM
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Humm.

I did indeed read about the fan being always ON, but not about problems with the burners...my understanding is that they're getting normal heat in this house, just the fan is stubbornly always ON. GAVolunteer pls confirm.

I'm in the middle of getting dinner for my gang, then off to basketball practice with my son. I'll check the forum again at night after my return and will post the schematic.
 
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Old 02-20-08, 04:07 PM
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The schematic...explained



Notice the blue circles, they are the coil and N.C. contacts of the heating speed of the fan relay. If coil 2A is energized, contacts 2A open, else, contacts are closed. Notice the blue arrows, they represent power moving to the blower’s low speed terminal of the fan motor. If contacts 2A are closed, the fan runs on heating speed. If open, the fan is OFF.

Notice the green arrows. They represent 24V power that will be present ONLY if the thermostat is calling for heat. On a call for heat, gas valve is energized and fires up the burners…24V also reaches the Solid State Time-Delay Motor, which starts a 75-second delay period, at the end of which causes triac to interrupt the flow of electricity thru relay coil 2A at the point where I have drawn the purple X…this in turn causes contacts 2A to close and the fan kicks ON.

Notice the red arrows. So long fusible link 11C and high limit 7H are closed, so long a jumper exists between R and Gh…and so long the triac has not interrupted the electric flow (at the purple X), coil 2A remains juiced-up, keeping contacts 2A open and the blower OFF. This is what should happen where there is NO call for heat from the t-stat.
BUT, if 11C and/or 7H open, and/or the jumper across R and Gh is removed, coil 2A is no longer energized, contacts 2A close and the fan runs.

11C and 7H were tested today, and they were reported in good condition (N.C.)
The board may indeed be bad, but should not be condemned until by observation it is noticed if the jumper between R and Gh is present or not. If the jumper is missing, a jumper should be added. If after the jumper is added the problem persists (in other words, with the t-stat NOT calling for heat the blower remains ON even after the jumper is added)…only then could be ascertained that contacts 2A inside the FHR are stuck in the closed position and the board should be replaced. Not before.
 
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Old 02-20-08, 04:16 PM
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I sense some competition here . .

 
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Old 02-20-08, 04:33 PM
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And a friendly competition I may add...this being the forum of brotherly love.
 
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Old 02-20-08, 04:46 PM
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I used to live in NJ, near Philly

I got laid off from my HVAC work a couple weeks ago, and there's not a lot of work here. I'll probably have to move.
 
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Old 02-20-08, 06:14 PM
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Originally Posted by pflor View Post
Humm.

I did indeed read about the fan being always ON, but not about problems with the burners...my understanding is that they're getting normal heat in this house, just the fan is stubbornly always ON. GAVolunteer pls confirm.

I'm in the middle of getting dinner for my gang, then off to basketball practice with my son. I'll check the forum again at night after my return and will post the schematic.
What I meant was you can't have an open limit or fuse link and have the burners cycle on. Which narrows the problem to a sticking HFR.
 
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Old 02-20-08, 08:51 PM
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I did indeed read about the fan being always ON, but not about problems with the burners...my understanding is that they're getting normal heat in this house, just the fan is stubbornly always ON. GAVolunteer pls confirm.
The burners cycle on and off and the house is getting normal heat.

I'll post a picture early next week.

THANKS for all of the info, diagrams and tips.
 
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Old 02-20-08, 10:39 PM
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Originally Posted by mbk3 View Post
What I meant was you can't have an open limit or fuse link and have the burners cycle on. Which narrows the problem to a sticking HFR.
You're right, as you of course knew.
 
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Old 02-21-08, 04:47 AM
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Originally Posted by Energywise View Post
Disconnect thermostat and see if fan still runs...

My guess would be its not the t-stat. It's the fan and limit control or the fan relay is stuck...the fan relay is the cube like box on the control board in blower capartment.
HUMMMMMM

LOL
 
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Old 02-21-08, 03:30 PM
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Originally Posted by Energywise View Post
HUMMMMMM

LOL
Yep you were right on me thinks. I wasn't doubting you just trying to clearing up a little misunderstanding of where the furnace was in the cycle.
 
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Old 02-22-08, 06:11 PM
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The HFR seems to be the culprit. I tapped on the HFR and the fan went off. When I turned the power off I heard a "click". When I turned the power back on, the fan came on. Repeated the sequence several times.

The HFR is soldered to the circuit board with 4 or 5 connectors. All are straight connectors and it "SEEMS" that the HFR would be "fairly easy" to remove and replace.

I did notice a flat head screw on the side of the HFR. I did not mess with it since I did not not what it did.

Can the HFR be replaced or must the entire circuit board be replaced?

Pictures:





What's the next step?
 
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Old 02-22-08, 06:23 PM
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First time I've tried to upload photos. I used MyPhotoAlbum.com. It would only let me post a link for thumbnails.

What site is the easiest to use?
 
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Old 02-22-08, 09:07 PM
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Here are 2 sites I use for photo uploading (I take turns between them)
http://www.freeimagehosting.net/
http://photobucket.com/

Whatever happened to the jumper between R and Gh? is there one or not?

Regarding the HFR, it is probably soldered, I do not think they were made to be replaceable. You will probably have to buy a new board since tapping onto it to get the blower running is something that will carry you just so far before you get tired of doing so.

But even if you could remove it, it's a part that likely you won't be able to find a replacement for.
 
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Old 02-23-08, 04:34 AM
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There never has been a jumper between Gh and Red. This is the way I found it.
 
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Old 02-23-08, 06:45 AM
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Well...give it a shot! Since this is a printed circuit board, maybe it's internal...then again...maybe not. What do you have to lose? The alternative is a board replacement.
 
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Old 02-23-08, 07:08 AM
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Just a thought, if yer on a budget. I had a problem with my furnace. Wouldn't do the same thing twice in a row, sometimes worked, sometimes not. Narrowed it down to the control 'box'. Pryed that sucker open, un-soldered the relays, cut the little plastic covers off, lightly burnished the contacts (how did I ever find that 20 y/o burnishing tool anyway??), hot glued the covers back on. Worked fine for over a year. May still be working, sold the house a year ago.

Took some time, but better than $125 for a new box.
 
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Old 02-23-08, 07:27 AM
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Very nice Gunguy...very, very nice.

A workout, but saves from the soldering, which is likely tough to do in tight quarters, such as a board.
 
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Old 02-26-08, 07:56 AM
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Another try at uploading pictures using freeimagehosting.net.





I just got back in town. I'll try the jumper and report back.

Since I'm helping out a friend, I want to be sure that If i cannot repair/replace the HFR, that I can quickly replace the Circuit Board in case I cannot replace the HFR or if I screw something up. Don't want her to be without heat for several days.

Does anyone have a part number for the circuit board or can you direct me to a site that will have it?

Carrier Model 58GP075-2 Series 311

thanks.
 
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Old 02-26-08, 09:16 AM
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Parts for Carrier, Bryant & Payne:
http://www.totaline.com/

The firewall here at work prevents me from being able to see/download pics. I'll check your posting later at home.
 
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Old 02-26-08, 09:23 AM
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Just arrived, from a totaline parts specialist:

All requests for Carrier/Bryant parts can be done thru the main number. 1-800-973-3345 and talk to a parts specialist and they can also get you to your local Totaline store.
 
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Old 02-26-08, 11:54 AM
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GA:
The tiny metal clip that shows on the board in between terminals R and Gh is likely the jumper I've been talking about, and if so, it is an internal jump. Try anyway putting the external jumper I suggested...one never knows...hopefully the clip is defective internally (though I doubt it).

The pic you posted does not help me tell if the HFR is removable. I doubt this too. But try gently pulling it.

At any rate, it all seems to point out at you needing a new board. Sorry!
 
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Old 02-26-08, 06:17 PM
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Now if you're really on fire about this project and want to save the money the board would cost you, you may want to consider adding a fan-relay yourself. All you'll need is a standard relay that runs on 24V (the coil) and use one set of N.O. contacts from it. The two ends of the coil will connect, respectively, to terminals W and C on the board. As for the contacts, cut the red power wire that juices up the blower on low speed, add male quick connectors to these two ends, and plug onto each one of the two ends (female/spade quick connectors) of the N.O. contacts.

You won't have that nice delay in the fan operation (in other words, it'll kick ON as soon as the call for heat comes from the t-stat), but is better than having that fan run 24/7.
And if you really want to get fancy, I can teach you how to add a timer to this add-on circuit (though the expenses will start to add up), or a Honeywell L4064 in lieu of the relay & timer combo.
 
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Old 02-26-08, 09:19 PM
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Thanks for all of the suggestions.

I'll try the jumper.

The HFR appears to be soldered to the board. Last week, I unsrewed the board from housing and looked at the back of the board. The HFR is soldered to the circuit board with 4 or 5 straight connectors.

There is a flat head screw on the side of the HFR (facing the LIM-1 & LIM-2 connectors). I did not unscrew it since I was leaving town the next day.

It's possible that I can get the cover off the HFR and see if the inside somehow unplugs or if the contacts can be serviced somehow.

Will keep you posted.
 
  #36  
Old 02-27-08, 07:47 PM
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Pflor, I was thinking about the offboard relay idea and thought that as a safety it might be better to go with two offboard relays in case someone trys to energize the fan to ON while the heat is calling which might burn out the motor if it's trying to engage both speeds at once.

Anyway I drew something up that could replace both relays, tell me if you think it looks okie:

http://www.coffeepower.net/relays.jpg

Michael
 
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Old 02-28-08, 01:58 AM
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niiiice...very nice
We have not heard from GA recently though. He may opt for a board after all. We'll wait and see.
 
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Old 02-29-08, 09:51 AM
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Thanks for all of the suggestions, diagrams, etc.

I called the 800 number pflor gave me. They said the HFR was not a replaceable part. She gave me the part# for the board - HH84AA020. She said it was a common board.

The replacement board I found on the internet was an ICM271 for about $46 including shipping. Sounds like the easiet way and cost does not seem unreasonable.

Any comments or suggestions about installing the board. It seems fairly straight forward.




Again, thanks for all of the help.
 
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Old 02-29-08, 10:16 AM
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Congrats!
$46 including shipping is indeed very reasonable.

And as you say, its installation is pretty straightforward.

Good luck!
 
 

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