Ask Experts Questions for FREE Help !
Ask
    Teacamp999's Avatar
    Teacamp999 Posts: 2, Reputation: 1
    New Member
    		  
    #1

    Jan 11, 2013, 10:02 AM
    What part makes furnace come on when triggered by thermostat?
    I have a 1990 model Coleman/Evcon 3500a811 furnace. It won't always come on when triggered by thermostat. We have changed thermostat and replaced disconnect. Need to know what else could be causing problem. Please help.
    ma0641's Avatar
    ma0641 Posts: 15,675, Reputation: 1012
    Uber Member
    		  
    #2

    Jan 11, 2013, 11:43 AM
    In units that old, it triggers the main gas valve. The valve opens, ignites from the pilot and then the fan relay comes on at a set temperature. Do you have a pilot light lit?
    Teacamp999's Avatar
    Teacamp999 Posts: 2, Reputation: 1
    New Member
    		  
    #3

    Jan 11, 2013, 12:04 PM
    Quote Originally Posted by ma0641 View Post
    In units that old, it triggers the main gas valve. The valve opens, ignites from the pilot and then the fan relay comes on at a set temperature. Do you have a pilot light lit?
    I'm sorry I forgot to specify that my furnace is electric. But thanks for your rapid response. Can you help?
    Grady White's Avatar
    Grady White Posts: 1,417, Reputation: 59
    Ultra Member
    		  
    #4

    Jan 11, 2013, 05:51 PM
    In an electric furnace there is a series of relays. 24volts from the transformer, through the thermostat, & to the coil of one or more relay(s). When the relay closes power is applied to the heating element(s) & fan. Without a wiring diagram or being able to actually see the furnace controls, I can't begin to guess the configuration of your particular furnace.
    mygirlsdad77's Avatar
    mygirlsdad77 Posts: 5,713, Reputation: 339
    Plumbing Expert
    		  
    #5

    Jan 11, 2013, 05:57 PM
    Grady is spot on. I will just add that many times the relays on electric units will be called sequencers on the wiring diagram. Odds are you have a bad sequencer/s.
Not your question? Ask your question View similar questions
 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

My 7 year old furnace is heating fine, but when I click on the thermostat, it makes a [ 1 Answers ]

My 7 year old furnace is heating properly, but when I click on the thermostat it makes a buzzing noise, then when I turn down the thermostat it stops.

Thermostat blank and furnace makes a buzzing noise [ 0 Answers ]

Yesterday morning I noticed that the thermostat was blank. I assured it had gone bad. I replaced it but the AC still would not come on. I went downstairs and the furnace was making a buzzing noice. I took the cover off and replaced a small fuse but still nothing. Help please

Fedders thermostat from 1978. Part no 19-03-088900001. Controlling elec furnace and a [ 1 Answers ]

Fedders thermostat installed 1978. Elec furnace and a/c unit. Three parts: cover, middle plate and wall plate. The middle plate separates from the wall plate. I cannot locate the mechanism to release the middle plate from the wall plate so I can see the wiring. Help appreciated.

Shooting triggered by intimidation [ 6 Answers ]

State: GEORGIA Situation: Shooting This is the situation so far: there was an argument at an underground illegal poker house between two separate small groups. The argument boiled down to two people, let's call them Fred and Barney. The argument gets very heated and Fred pulls a gun out at...

Can late periods be triggered? [ 1 Answers ]

Hi Ihave missed my period for the last two months and a scan I did proved that I am not pregnant.the doctor however prescribed PROVERA TABS to help trigger my periods to come.two weeks after medication and still nothing. I want to get pregnant but am confused. What could be the problem?

View more questions Search