2 year old Furnace problem

[TomS]

Hi,

The Gas Furnace (forced air) came with the newly built house (2 years ago). The Furnace worked great for the past years, but I tried to turn the heat on a day ago and the heat wouldn't come on. The Furnace's diagnostic light is steady green (code says that it's in normal working condition). I've replaced the Thermostat (planned on getting a digital controller anyway) but didn't fix the problem.

Note: AC works, Blower Fan works... just no heat. No indication of the Heater starting.

The Furnace is noted as automatic pilot, so not much to do there as far as lighting the pilot light. Anyway, I've followed the instruction and powered down the Furnace & powering it back on & adjusting the Thermostat to trigger heat but couldn't get it to go.

Worse comes to worse, it's under the 5yr warranty but I'm almost certain it just needs a little cleaning of some sort to get it to go. I would much prefer not having to spend $150.00 for a tech to come out & do a 5 minute clean job.

Any pointer or helps greatly appreciated!

[Randd01]

Don't you have a switch on the bottom of the thermostat that you have to switch from AC to Heat? Most do.

[HeatMan]

Do you have a model & serial number?

[TURTLE]

This is Turtle.

Without a Model number & Serial and brand name. We are shooting in the Dark here.

Well Ok here is a shot.

I think you have a broken 24 volt control wire going from the furnace to the thermostat. It will usely be the white wire but look where the connections are at the furnce for being a bad connection. The only way to not get a sound of no kind out of it when you turn on the heat or jump out the thermostat is a loose or broken connection of the 24 volt wires. The only way to get it to do nothing when you turn it on is to not send power by way of 24 volt signal to it.

TURTLE

[TomS]

Thanks for the info.

It has Quiet Comfort label on the Furnace.

You are correct in making the assumption that nothing triggers on the Furnace end (no attempt to start... nothing) when the Thermostat is switched to turn the heat on & the temp set higher than the room temp.

I will look at the installation guide & see verify that the connection is good. If not, I'll make the adjustment (with the circuit off).

[TomS]

Yes and it was moved to the Heat position when I tested it. While moved to the AC position, the air works great. The fan works great. The only problem is that the Furnace does nothing when moved to the heat position.

[NULL]

[TomS]

I saw the fuse for the blower logic board, but didn't see any other accessible fuse. Guess I'll have to double-check.

Thanks.

[TomS]

It's noted on the Manual as the central controller fuse, which tested out fine with the continuity test.

[TomS]

It wasn't working prior to the replacement.

[TomS]

The Fuse on the Controller board test fine.

The Circuit Breaker when on the ON position, does provides power to the switch on the Furnace. My guestion is, can the Circuit Breaker provide enough power to turn on the switch but not enough to start the Furnace? Meaning bad Circuit Breaker?

The connections from the Thermostat to the Furnace looks fine. However I have no way to confirming that the W wire isn't defective. However I do have an additional wire that connects to the C connector on the Furnace end, which isn't used at the Thermostat end because my system doesn't support the configuration. Would it be okay to temporary swap the W wire with the spare wire (or with the Blower wire) and test for continuity? The look identical thus I assume they are the same guage.

[SQLit]

continuity?

Generally if a breaker closes and provides power at all the breaker is ok.

[Zypher]

Tom;

You can test the furnace by disconnecting your thermostat from the furnace (at the furnace) and use a piece of 18 gauge wire from the "R" terminal to the "W" terminal to complete the circuit. If your furnace is a 'newer' furnace, you will have to close the blower door to complete a 'safety switch' connection. If your furnace doesn't work after completing the circuit from R-W, then your problems in the furnace and not the thermostat. At that point I'd check the phone book for a qualified licensed heating contractor to check it out.

[TomS]

Makes sense, thanks.

thermostat.

[Stormin Mormon]

You just need a VOM with very long leads. So you can test the wire for continuity.

Sure, use a different wire. The electricity won't know the difference.

[TomS]

I swapped the G (Blower) wire with the W (Heater) wire at both ends. Power up the Furnace via Circuit Breaker & switch... The Blower works fine when triggered by the Thermostat. So that about eliminates the wiring & thermostat out of the equation. Rewired the G & W wire to it's original state... a little closer to the problem I guess.

continuity?

[Stormin Mormon]

What happened when you jumped W and R at the furnace?

[HvacTech2]

Hi TomS, hope you are having a nice day

On 04-Oct-04 At About 06:09:12, TomS wrote to TomS Subject: 2 year old Furnace problem

T> From: "TomS"

T> Hi,

T> The Gas Furnace (forced air) came with the newly built house (2 years T> ago). The Furnace worked great for the past years, but I tried to T> turn the heat on a day ago and the heat wouldn't come on. The T> Furnace's diagnostic light is steady green (code says that it's in T> normal working condition). I've replaced the Thermostat (planned on T> getting a digital controller anyway) but didn't fix the problem.

T> Note: AC works, Blower Fan works... just no heat. No indication of T> the Heater starting.

T> The Furnace is noted as automatic pilot, so not much to do there as T> far as lighting the pilot light. Anyway, I've followed the T> instruction and powered down the Furnace & powering it back on & T> adjusting the Thermostat to trigger heat but couldn't get it to go.

T> Worse comes to worse, it's under the 5yr warranty but I'm almost T> certain it just needs a little cleaning of some sort to get it to go. T> I would much prefer not having to spend $150.00 for a tech to come T> out & do a 5 minute clean job.

T> Any pointer or helps greatly appreciated!

Other than cycling the unit as you have already done There isn't much else you can do without knowing how the system works and how to troubleshoot it. Todays furnaces are a lot more complicated than the older ones and some even require special tools to hook up and find fault codes.

-=> HvacTech2

[HvacTech2]

Hi TomS, hope you are having a nice day

On 04-Oct-04 At About 23:48:54, TomS wrote to TomS Subject: Re: 2 year old Furnace problem

T> From: "TomS"

T> Yes and it was moved to the Heat position when I tested it. While T> moved to the AC position, the air works great. The fan works great. T> The only problem is that the Furnace does nothing when moved to the T> heat position.

Hmmm, you didn't by chance change the thermostat over the summer did you?

-=> HvacTech2

[TomS]

Had a Furnace Serviceman stop by and he tested the Furnace out. He concludes that the Gas Valve is the problem. Apparently the newer Furnace has more technology built into the Gas Valve component. He then called the Manufacturer the following morning and confirmed the problem.

I've contacted the Builder since and was told that the Builder send someone over with the part to repair the Furnace free of charge, since the house is just little over 2years old.