[Tony J S 1]

Carrier Gas Furnace 58ZAV115-16 with replacement Circuit Board ICM 282, which replaced a HK42FZ011 board. Probably installed in 2000 or early 2001.

1. When 120V supplied to the furnace through the "field installed" external switch, the furnace blower motor comes on and runs for about 2 minutes and shuts off. Furnace will remain off after this initial run as long as 120V is supplied. Cycling the 120V supply on and off will repeat the above malfunction.

Error code appears to be 33. 3 slow flashes, followed by 3 quicker flashes.

Error code then changes to 31, after blower motor has cycled off.

New ICM 282 board came with a suggested test sequence. Not able to carry out do to above.

2. Problem occurs with and without thermostat wires attached. Problem was same with original board. Check of all Limit Switches, DSS, FRS's, wiring OK. Checked HSI, FPE, GV solenoid for continuity, OK. IDM runs OK when wired directly to 120V source. Checked wires for correct assembled pin connections in new board plugs, appears OK. Ground to furnace sheet metal frame is good.

3. Replaced 24VAC transformer, thinking that the original's output appeared somewhat low when checked at outputs from CPU. Open circuit trans voltage was Ok. New trans made no difference and instruction sheet w. new Circ Bd claims it is very tolerant of voltage hi/lo conditions.

4. Separated all the wire harness leads and checked while moving them, nothing.

:(

[KC13]

Re-check your codes - short flashes are first digit, long flashes are second digit. Looks more like 33 followed by 13. Post description of these codes.

[Tony J S 1]

Hi, KC13

The only code that appears at this point is 33. (three short, three long). And as you pointed out, this changes to 13 after the blower motor cycles off.

Happy New Year
Tony

[KISS]

33 is probably:

33 LIMIT CIRCUIT FAULT - Indicates a limit, draft safeguard, flame rollout, or blocked vent
Switch (if used) 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 and BVSS require 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).

[MarkwithaK]

Check your high limit switch!

[Tony J S 1]

Hi, MarkwithaK

Question: On this furnace, there is a limit switch, no "hi limit switch". The LS (auto reset) is in series with 2 manual reset Flame Roll Out switches. There is continuity through these 3 items, with a measured resistance of just a few ohms.

The Limit Sw. is installed in the heat exchanger area just above the burners. All of the other switches/safeties appear to be functional, in so much as an ohm meter indicates continuity through the entire circuit, with just a few ohms of total resistance. The Draft Safety Switch closes and completes the circuit with the other components in its loop when the IDM is hot wired.

The only thing that seems to make sense to me, is that the Circuit Board is leaking some current through some function that I have failed/can not identify, resulting in the unit running in a "safe mode"(?), main blower only.

[MarkwithaK]

The LS s in fact your high limit switch. Why they no longer call it a High Limit is beyond me. When you checked for continuity through the switch did you pull the wires from the terminals to check. If not you will get a false reading.

[Tony J S 1]

Hi, MarkwithaK
1)In desperation, I checked each individual copper wire in the harness, separate from the Circ Board and whatever it was plugged into. Even wiggled the wires a bit. If anything was amiss, I missed it. That is extremely unlikely.
2)I then rechecked the 2 safety circuits (in this case, orange wires, and red wires respectively, disconnected from the Circ Bd. Resistance measured with an ohmeter in both circuits is very small, a few ohms. In the orange circuit, I checked repeatedly for these conditions: Open when IDM is not operating, Complete when IDM is hot wired to a 120V soource.
Peace,
Tony

[KC13]

Check the service label and/or circuit board for "component test" sequence. Perform if available, and report results.

[Tony J S 1]

Hi, KC13

There is a multi-step check procedure ("Component Self Test") that is included with installation instructions for the replacement Circuit Board.

It involves leaving the thermostat wires off their posts and jumpering from the Test/Twin terminal to Com/24V.

This test procedure is not available at this time, due to the main blower motor being switched on by the Circuit Board ECM after a short delay (10 to 15 seconds) as 120V current is supplied to the system.

[hvac1000]

due to the main blower motor being switched on by the Circuit Board ECM after a short delay (10 to 15 seconds) as 120V current is supplied to the system.

Disconnect motor load and perform test.

[hvac1000]

Disconnect main blower leeds and do the test. The blower motor wires do not need to be connected for a count down operation test. Everything will work except the relay will not activate the blower since the wires are not attached. Ones test is performed see the codes if any and post. Naturally turn off furnace to prevent overheating.

Blink codes

http://www.icmcontrols.com/downloads/ICM282-fcl.pdf

Board for 80%

http://www.icmcontrols.com/downloads...80furn-lab.pdf

Do a ground check from panel to furnace then to board. A missing ground will cause major problems. Do not just look for the bare or green wire but test to make sure the ground is continus from main electric panel to the circuit board. Corossion under the connection or ground screw or device is a ground killer and trouble maker.

Also make sure some idiot did not cut the ground wire for the blower motor or inducer motor when and if they were ever replaced. The CPU/board is very sensitive to all forms of grounding and will really give you a headache trying to find the problems.

These boards are also sensitive to 60 cycle phase distortion/polarity reversal. Switch the two 24 volt conductors on the board to see if that helps.

Post back with results