Bad sequencer or fan relay?

It may be but the fan control may be set to turn off at to high a temp, or theres a short between ;r; and g at the stat or furnace or sequencer, IF it runs through it. A limit or rollout switch may have failed but this will keep the unit from firering. Check for a manual blower switch that may be on. At stat it should be at auto and alsso at the fan control. A stuck relay is always possible,

you need to set either the switch on the back of the tstat to HE NOT HG or in configuration mode you want the "tstat controls the fan" not "equipment controls the fan" or ELECTRIC HEAT NOT GAS HEAT.

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

Electric strips have what's called a Sequencer also called a stack relay it's a relay that brings on the fan and strips at the same time on a call for heat. If you have more than 5kw you will have more than one Sequencer in fact you will have one for every 5kw.(only the first one will bring on the fan) It could be your high limit making your unit stop heating before it reaches the temp set on the T-stat. Check and see if your getting proper air flow across the electric strips your filter could be dirty. If not remove the cover from your T-stat and take the red and white wires off and twist them together this will bring on the heat then just watch the unit for about an hour if no problems then you have a bad T-stat. If the unit does cut off and the fan seems to be blowing fine you might have a bad high limit switch.

hope this helps........

The model of T-stat you gave comes up as a discontinued model on Honeywell's web site, but it looks to be a manual stat that type of stat would have to be wired with a summer winter switch with electric heat, allowing it to turn on the fan with a call for heat. If yours is a programmable T-stat you would need to select electric heat or in the installers set up change the default setting for fan from unit controls fan in heat to thermostat controls fan.

I suspect a bad fan relay or bad fan control. Maybe the longer the control or relay is in the on position the more chance of it sticking on.

You have a blower relay in the furnace that's probably bad. In the heat mode the blower is on a temperature relay, in cooling mode the blower has to come on immediately so there is another relay for cooling. The green wire on the thermostat feeds that relay, so if you go to the furnace and shut the power off and find the green wire from the thermostat that feeds that relay and replace it, being careful to mark all the wires before removing them, also the relay terminals have numbers for identification.

You need to check the low voltage side to see if the t-stat is calling for heat. If it is, it is either the sequencer or a fuse to the heating elements (older model). But most likely the squencer. If you have a meter, you can check to see what side of the sequencer is burnt. Could also be a relay depending on the model number. If you get me the model number, I can send you a copy of the wiring diagram for the unit. This is the brand that I deal with.

If it were the sequencer, the heat wouldn't come on at all but the fan would blow. It's the fan relay but it could be the t-stat again. If you get a power surge when the unit is running, it can short out that portion only but typically, it will short out either the heat or the cool side depending on what is running not just the fan.

If the fan runs in the ON setting then you have a bad fan relay for the heat mode.
Did you install the t-stat before or after the problem?
If after, you have a bad fan relay.

It sounds like you T-Stat is messed up. Look in your manual to see if there is set up instructions. If not I would change the T-Stat.