DIY Home Improvement Forum banner

Blower fan runs constantly

44K views 67 replies 12 participants last post by  ahome3688 
#1 · (Edited)
I've got a Carrier downdraft htg/fan coil unit, 1990 Model No. 58DRC080-JB.

Unit was working fine. Last weekend main power to the house went on and off about 5 times in 1 hour. Next morning the blower kept running even after the heat setpoint was satisfied (and burner properly cut off). I made the blower stop by opening the access panel to trip the safety switch.

To test for Tstat damage I completely disconnected the thermostat wires - The blower still runs constantly when the panel door closes, so I think Tstat isn't the problem. Heating and cooling both function properly from the Tstat, just that the blower stays on constant; I have the access panel ajar until I want to run it.

Looking at the unit and the wiring diag inside the panel, I wonder if there's an airflow safety switch or temp safety that got shorted out.

Anyone heard of power outage causing a fault like this before?

Thanks in advance for any ideas on troubleshooting, or other advice.
Made the mistake of asking on hvac-talk forums, just for any known DIY sites for homeowners, and within mins, a handful of unfriendly posts and the thread was closed. :huh:
-Mark
 
See less See more
#42 ·
Well if the new board's bad, so be it. Rare, but happens; I'd like to rule out other possibles before asking the merchant for exchange or return.

Something I don't understand on P. 3 of the new board's App guide: attached screenshot

The right column of Blower Operating Modes seems to describe how the unit normally used to operate. Not cut any resistor or jumper unless it was cut on the old board... well, the old board doesn't have an R17. I've got a higher-res digcam back in service, I can post pics of the orig board.

I might try calling ICM Controls to see if they have any tech support. Don't know what to make of the jumper on the orig board between the GH-and-R terminals, vs. JW-1 on the new board. -Mark
 

Attachments

#43 ·
tshooting ICM controls

Ok consensus board bad.
ICM Controls gave good support. JW-1 on new board is a zero-Ohm jumper GH to R, just like orig. Confirmed R17 should remain as-is.

Tested SEC-1 to SEC-2 for 24VAC -yes. Tested Line1 to Line2 for 120VAC -yes. Transformer's good.

He had me jump GAS-1 to GAS-3 and jump Lim-1 to Lim-2 then call for heat by jump R-to-W. Said if the fan still doesn't start the board's bad.
The burner fired right away, but no fan start even over 2 mins later. I confirmed no 120V on COM-LO & COM-HI so it's not wires/connectors.

Offta exchange the board. Thanks for all the help here guys-- I learned a lot and am grateful. -Mark
 
#47 ·
Ok consensus board bad.
ICM Controls gave good support. JW-1 on new board is a zero-Ohm jumper GH to R, just like orig. Confirmed R17 should remain as-is.

Tested SEC-1 to SEC-2 for 24VAC -yes. Tested Line1 to Line2 for 120VAC -yes. Transformer's good.

He had me jump GAS-1 to GAS-3 and jump Lim-1 to Lim-2 then call for heat by jump R-to-W. Said if the fan still doesn't start the board's bad.
The burner fired right away, but no fan start even over 2 mins later. I confirmed no 120V on COM-LO & COM-HI so it's not wires/connectors.

Offta exchange the board. Thanks for all the help here guys-- I learned a lot and am grateful. -Mark
told ya
 
#46 ·
Go get a board and stop micro managing every detail.

My kid used to help me in my business 'til he got his EE degree. Kid used to be the most practical minded HVAC tech around. Now since he graduated university and went to work he needs an inter net connection and a spread sheet to change a faucet.
 
#49 ·
Wrap up

With warnings all over this site about following advice given here, I didn't feel the least obligated. I participate in several forums, from hobbies to computers and it's interesting how worked up ppl can get; that's all part of it.

Mon this week i got the replacement board from ebay seller "thermalresources" and the furnace was working in 15 min. It came with 3 Amp fuse installed. The first one didn't--which made me wonder if it was truly new & unopened. They sell the board cheap (under $50 incl ship) but I wouldn't recommend; slow cust service to replace the defective board cost me an extra week.


 
#57 ·
Furnace false starts on shutdown??

When my furnace is shutting down after heating, it tries to restart for a second or two. It does this about 4 or 5 times each shutdown. A local tech called it a "false start", he changed the gas regulator and ignitor(wrong terms I'm sure).

I ordered a new board after reading this thread because I was having the same constant running problem for some time. This morning it decided to shut down by itself, but returned to the false starting problem.

Any Ideas?

Thanks
Ww
 
#58 ·
When my furnace is shutting down after heating, it tries to restart for a second or two. It does this about 4 or 5 times each shutdown. A local tech called it a "false start", he changed the gas regulator and ignitor(wrong terms I'm sure).

I ordered a new board after reading this thread because I was having the same constant running problem for some time. This morning it decided to shut down by itself, but returned to the false starting problem.

Any Ideas?

Thanks
Ww
bad thermostat.
 
#59 ·
That is what I thought too. I changed that first, sorry...I forgot to mention that.

This morning it has worked properly a couple of times and a few times it did the false start.

I should get the new board this Sat or Monday. Probably will not have much time to troubleshoot as I have to leave town for work.

Thanks for the speedy response.
Ww
 
#61 ·
I was under the impression that you had already installed the new board. Yup, it's a control problem, so either the board or the stat is telling the furnace to come on and shut off.

You can bypass the stat, completely removing it from circuit, and control the furnace at the board and see if the problem persists. I'd be willing to bet it does and that the board is the problem.

Let us know and we'll walk you through how to do it.
 
#62 ·
New board installed

Ok, board installed. Applied power at breaker box, then turned on switch on side of furnace and as soon as I did that a relay threw a quick spark. The thermostat was off.

The relay is the one on the left in the picture. This is a picture of the old AMF one, the new one is a Potter Brumfield one. The relay on the board is labeled CRF. Two things...I don't know if I'm using proper terms here...I think it is a relay and I don't know what CRF stands for.

The fan will only turn on with the Thermostat in the ON position. In Auto, the burner lights, but no fan.

Ideas? seems to be similar to the old board.

Thanks
 

Attachments

#63 ·
Could the board be shorting out some how within the bracket holding it? I also noticed the pilot light seems to be a little longer...maybe 3 or 4 inches, could this have any affect on the running of the fan? thanks for the help, I wish i could get the auto mode working...don't like the fan running all the time.

Bill
 
#64 · (Edited)
blower satys on

i have an electric furnace and the blower stays on i put a new relay in NO GOOD i put two new limit switches in NO GOOD THERE is a stack that i havent replaced.PLEASE HELP:eek::eek::eek::eek::eek::whistling2::whistling2::whistling2: it says coleman on the door but MORT EX on the blower 1988 trailer furnace
 
#67 · (Edited)
Hi. I need an advice with my Carrier 58gp125-111JA furnace before I buy a new board (PN SECO110018-00). The furnace's blower runs constantly now with the fan switch is in Auto or On. Heating works fine but the blower does not turn off after reaching the preset temperature. Gas turns on after temperature starts to fall.
I have Honeywell thermostat Pro 4000. I disconnected Tstat but blower still running. The blower starts running right after turning the main power switch on.
When I turn the main power switch or the blower door switch ON, I hear no relay click and I do not see any evidence of a small sparks in the relay. The small sparks come when I slightly hit the relay with a screwdriver.

Should the blower's relay be ON position in default? or I should hear/see repay turning ON after powering? Should it blow without Tstat?
Any sensor that I need to test before replacing the board?

Would the board ICM271 be a right replacement for SECO 110018-00?
Tnx.
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top