Page 3 of 3 FirstFirst 123
Results 27 to 33 of 33
  1. #27
    Join Date
    Oct 2009
    Location
    new jersey
    Posts
    246
    Im old enough to have worked on that control 20 plus years ago. The purpose of the heater in the fan control is when you start up heat in morning with cold ra temp the fan control will cool off enough to stop fan.the heater keeps the fan on with a w call

  2. #28
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    212
    After reading all of this, I'm left wondering how other furnaces using
    the more common, no-heater fan/limit don't have short-cycling on
    occasion. But it also makes it more clear why everybody now uses
    timed fan-on, fan-off.

  3. #29
    Join Date
    Jan 2009
    Location
    Salisbury, Maryland
    Posts
    140
    A pic of it would be great. At first I thought you were talking about one of the fan limits with an adjustable high limit, fan on and off tab that rotate when the HX gets warm but now I'm not sure. Either way, I'd do like T52 and check the temp at the limit and check your airflow. Its possible it could be bad but I'd confirm first because its not exactly common. You don't want to install a new one and have the same problem ya know.

  4. #30
    Join Date
    Jan 2009
    Location
    Salisbury, Maryland
    Posts
    140
    Nevermind, I didn't realize so many people had posted, and with pics....... lol Anyways, seems like alot of mobile home units with gas or oil use them. Some I've noticed get "hung up" when rotating and don't always turn blower on at right time. I'm guessing because someone in the past had screwed with the dial and got it out of whack?

  5. #31
    Join Date
    Feb 2004
    Posts
    2,458
    Nobody has mentioned energizing the tstat and have the blower come on after a few seconds when the gas is off. That is a sure indication there is a "heat assist" fan switch (control) installed.

  6. #32
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,030
    Most furnaces with these fan & limits are close to 20 years old and older. One should check the heat exchanger closely.
    Beware of advice given by some guy on the Internet.

  7. #33
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    3,141
    Quote Originally Posted by ClimateCntlJohn View Post
    Nevermind, I didn't realize so many people had posted, and with pics....... lol Anyways, seems like alot of mobile home units with gas or oil use them. Some I've noticed get "hung up" when rotating and don't always turn blower on at right time. I'm guessing because someone in the past had screwed with the dial and got it out of whack?
    No that's just a really common failure on the fan/limit combos. They get weak over time from rotating and can't push through the set point or snap back through it(so the fan either won't come on or won't turn off), don't try to wd-40 or oil them because it doesn't help, the metal is just fatigued.

Page 3 of 3 FirstFirst 123

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event