Sometimes Air Handler Fan Not Coming On In "AUTO" - HVAC - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC


Thread Tools Display Modes
Old 12-08-2010, 07:38 PM   #1
Join Date: Apr 2010
Posts: 14
Rewards Points: 10

Sometimes air handler fan not coming on in "AUTO"

Hi everyone. New here and hoping to get some help. The problem I am having is that sometimes in "Auto" mode, the air handler blower fan doesn't run. Thermostat calls for heat, the furnace starts and the pipes are hot. The problem is that the blower fan doesn't start by itself if I set the fan to "Auto" mode. The problem doesn't always happen and it seems to happen more in the mornings. Initially I suspected that the problem may be with thermostat but replacing the thermostat did not help. If I turn it to the "FAN ON" position it works great but fan will not kick in automatically the "FAN AUTO" position. What should I do?

I called the oil company HVAC tech and when he came everything was working and he was not able to see the problem. Was charged $90 for the visit. I am hoping someone can help me here.

The air handler is made by FirstCo and is about 10 years old.

Model is 24MBXR-3HW

Fan coil Unit 27JF


dvsrikanth is offline   Reply With Quote
Old 12-08-2010, 08:13 PM   #2
JJboy's Avatar
Join Date: Oct 2010
Location: Austin - Texas
Posts: 1,402
Rewards Points: 500

Check the capacitor and blower fan terminals.


JJboy is offline   Reply With Quote
Old 12-08-2010, 08:27 PM   #3
Join Date: Nov 2010
Location: NE Indiana
Posts: 2,426
Rewards Points: 1,208
Blog Entries: 1

there is probably a relay in the AH. The relay may be on a control board, or not. It may be failing. trace your wires back from the blower motor and find what they go to.
hvactech126 is offline   Reply With Quote
Old 12-09-2010, 10:56 AM   #4
Join Date: Dec 2010
Location: Reno, NV
Posts: 49
Rewards Points: 25

yea sounds like the relay or fan switch going out. if its a fan switch check the setting on it to see when the fan is suppose to come on. if its a relay on the control board you have to replace the board to fix it.
hvac kid is offline   Reply With Quote
Old 01-06-2011, 09:35 PM   #5
Join Date: Apr 2010
Posts: 14
Rewards Points: 10

Problem did not happen for 3 weeks and it started happening again.

I am a new home owner and I have little experience doing this kind of work.

What is the best way to check the fan switch? Is this the part (safety switch) that gets pushed inside when the blower cover is in place?

Is changing the board a DIY job? How difficult is it?
dvsrikanth is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Fire ants coming into house through pipes in foundation -- need advice samalex Pest Control 15 03-22-2011 01:35 PM
Air handler blower doesn't work in "Auto" mode dvsrikanth HVAC 6 12-03-2010 01:13 PM
Heater fan not coming on in "AUTO" reptile411 HVAC 26 12-02-2010 10:48 PM
Toilet: water still coming from BOTTOM of Inlet Valve DIY Mom Plumbing 1 08-12-2008 12:43 PM
Replacing air handler - How to fit when form factors are slightly different?? hennyh HVAC 2 11-16-2006 08:23 AM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1