Heat - fan "on", no "auto"


Old 11-16-00, 06:50 AM
Visiting Guest
Posts: n/a

Outside gas furnace/Ac unit. AUTO setting will no kick the fan in at any temp. Must use ON periodically throughout day. The furnance still ignights per thermostat setting. New Honeywell digital therm. (electicity - circuit breaker is on. Replaced outside fuses (2) leading to H/AC unit)
Sponsored Links
Old 11-16-00, 02:48 PM
Visiting Guest
Posts: n/a

You have a problem with your fan/limit switch or if the fan is controled through a board, the board may be bad.
Old 11-16-00, 08:39 PM
Visiting Guest
Posts: n/a


The furnace has a defective fan switch. Have this item replaced by a heating service agency asap.

Operating the fan manually, as you are currently doing, is fine but only for a limited amount of time.

A furnace with a defective fan switch is constantly cycling the burners off on the high limit safety switch.

When you turn the fan on manually to get heat into the house, it helps keep the firebox from becoming too hot, which is okay.

The problem is when you turn that fan off. Doing so at the incorrect time is not good for the furnace firebox.

With an outside located unit, it is impossible to correctly time those cycles at the thermostat. Continuing to operate the furnace in the manner you are may cause firebox damage.

Good Luck,
Old 11-18-00, 08:00 PM
Visiting Guest
Posts: n/a

The fan is turned on by either a fan and limit switch or a circuit board timer.
What Brand and age unit do you have.

It is safe to run with the fan switch on till you can get either of the above replaced.
Good Luck
Mr Foster

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

Thread Tools
Search this Thread
Display Modes