My furnace is a Carrier,about 9 years old. My blower runs but there is no heat. Have done some research so I replaced the HSI because there was a white spot on it and it was not lighting up. It still is not lighting up. Could someone tell me what I should do next. Thanks.

Check for voltafge at the HSI. Then check for voltage at the board plug in.

If the board has a fuse check it also.
Have you replaced the thermostat lately?

Have not checked voltage. Is it supposed to be at 120v? Have not replaced thermostat but recently changed batteries. Checked fuse it was a 3 fuse OK. Where do I check the voltage on the board?

Follow the leeds bach to the board or unplug the HSI and test there. Set volt meter at 120.

How many blinks does your circuit board show for a fault code. Fault codes will be listed on the inside of the blower compartment door.

The led light is blinking a 3-3. Went and purchased a digital voltage meter. You can set it for AC at 200 or 500. I set it at 200, put the two probes where the HSI connects and it read a 0. Not sure if Im doing it right, sorry first home trying to teach myself.

HSI is 115 volt amp draw 1.0

33 LIMIT CIRCUIT FAULT - Indicates a limit, or flame rollout is open.

There is a wiring diagram inside the blower. It should also contain a blink code number list and fault.

? Is the blower motor you are talking about the main house blower or the draft inducer motor on the front of the unit?

It's the main blower at the bottom of the unit. Its big. It is a #33 , flame rollout is open, but it also states if open for more than 3 minutes it's a #13 lockout.? What does this mean, next step? Thanks.

13 LIMIT CIRCUIT LOCKOUT - Lockout occurs if the limit or flame rollout switch is
Open longer than 3 minutes.
- Control will auto reset after three hours. - Refer to #33.


33 LIMIT CIRCUIT FAULT - Indicates a limit, or flame rollout is open. Blower will
Run for 4 minutes or until open switch remakes whichever is longer. If open
Longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes
Status code #33 continues to flash until blower shuts off. Flame rollout switch
Requires manual reset. Check for: - Restricted vent
- Proper vent sizing - Loose blower wheel - Excessive wind
- Dirty filter or restricted duct system.
- Defective blower motor or capacitor. - Defective switch or connections.
- Inadequate combustion air supply (Flame Roll-out Switch open)

How do I know if I have any defective switches or connections? Vent sizing OK, blower wheel OK, filter OK. Do I need to manually reset flame rollout switch, if so where is it and how? Also why is there no voltage when I test the plug that connects to th HSI?

Flame roll out switch located near front of furnace right above burner area.

What is the little black wheel in front that says rotation on it?

That is the combustion/vent fan. It needs to be running for the unit to fire up.

So do you think I should replace it? Does that explain having no voltage on the HSI as well?

What is the little black wheel doing? Does it run/spin?

You need to test the motor on the fan for the little blower wheel before you replace it.

Its not spinning at all. And how do I test the motor on the fan.

Remove connector. Apply rated voltage to wires. Motor should be 120 bolts.

I applied my meter to the wires that plugged into the fan and it read 0.

Yiu are not getting voltage at the board. If you want to test the fan you need to apply 120 volts to the fan motor from another source.

Post the exact model number of your unit.