If your a Tech, I think you should be posting over here. :grin2:

http://hvac-talk.com/vbb/forumdisplay.php?1122-Tech-to-Tech-Chat-Residential

 

haha I think you answered your own question.. I wish i could do that.. :cheers: there are manuals that explain the operation of gas furnaces. when in doubt google it.

 

Moved thread to Tech to tech chat.

I agree that you need to stop and read the manual.

Twice, if necessary.

 

haha I read it way more than twice and im still stumped

 

i just graduated 2 weeks ago

 

Just out of curiosity, what percentage of your schooling was "hands on"?

 

Read it while at the furnace. Spend some time with it,,,,you'll figure it out.

 

Just graduated, how come your not riding with a senior tech? Anyway you did answer your own question, ventors running, switch is closed. When did the problem start, what changed and read the wire diagram closely. Then call the tech that's been at your company the longest.

 

That's the give a man a fish feed him for a day, teach him to fish feed him for life thing right. Or was it teach him to fish and he'll sit in a boat and drink beer all day. I can never remember which is right.

 

Give a man a fire, keep him warm for a night. Set a man on fire, keep him warm for the rest of his life.

 

Follow the sequence of operation.

 

Few questions:

Why would the inducer run if there if tstat wires are disconnected and there is no call for heat? A correct understanding of the sequence of operation would not be of help here as this is just wrong.

Nor are schematics the magic bullet, I'm finding, in modern systems as they don't really detail the sequence of operation; sending a leg ( or 2 or 3) of LV control voltage to the CPU at the same time it sends it thru the fuse and on to the limits and to red on the LV terminal strip.

What kind of furnace is it? 80%...90%?

This one might not be as easy as some of you are thinking.

 

Never said easy, but the op said the pressure switch was working correctly, then he changed it anyways. Blinking light says bad pressure switch and computers don't lie, must be a bad pressure switch.

Someone should have come right out and said go back to the basics of troubleshooting, just ignore the blinking light, if you know the sequence of operation and how to check the various parts and switchs you will find the problem.

 

Like I said I just graduated a couple weeks ago.. havent yet found a job in the hvac field I have only worked on a few furnaces ( not smartvalves) in my dads rental houses and diagnosed them just fine. I have no one to ask except a few classmates which I already did. I have also googled this till im blue in the face. The sequence of operation is burnt into my brain. I known the furnace has to sense the pressure switch is open first, the inducer starts, the pressure switch closes.

OK just answer this for me on the honeywell smart valve. are the set of contacts that send 120v to the inducer motor N.O. contacts when the tstat is on the off position or power turned off to furnace?

 

Let me ask you this. What would happen if the contacts were normally closed when T-stat is off?

 

Have you considered consulting with your previous instructor?

 

Oh crap! I missed the "SV" in the thread title, sorry.

Just run away as fast as you can. You will quckly come to despise the smart valve as most have.

The other members are being coy because this is an open forum that anyone can view.

I'd like to have a copy of the schematics for a furnace with a SV for my ongoing schematic studies; if anyone has one handy...

 

If you make a request for one in the Pro forums, rundawg would probably have one he would upload.

 

How many spade terminals are on the new pressure switch?

 

2 spade terminals

 

Its N.O. when the inducer is not running.

 

I am a recent HVAC tech grad learning the ropes. Working on an airquest gas furnace with honeywell sv9541. Inducer motor runs all the time even with t-stat completely disconnected from the board and I get no fire. I get a flash 2 error code, pressure switch stuck closed. I can get furnace to fire if I disconnect and reconnect one connection from the pressure switch.I tested pressure switch. It is opening when I kill power to furnace and closing when I restore power to furnace and I get a pressure of 1.2" w.c. The pressure switch is doing exactly what is suppose to do but I keep getting error code and inducer motor runs all the time when power is connected to furnace. I have even changed out the pressure switch and its still doing the same thing. Im thinking a couple wires fused together in the smartvalve?? Any ideas?

Most likley you have more then one problem! Circuit board to the smart valve for the inducer powers up with no call for heat. If you jumper R & W with power off and turn it back on and the pressure switch error shows can be the smart valve. The smart vavle only controls the heat side of the uint (sequence of operation) on call of heat. that's my two cents on your problem

 

Is the relay for the inducer embedded in the smart valve? If so could he ohm the contacts!! As you can see. I don't work on many furnaces? :grin2:

 

I did the contacts are closed.... changing out the valve if that indeed is a relay and not just a connection. the manual just says "line voltage connector"

 

Turn your smart valve to "on" position

 

Please tell me this valve is going the way of the thermocouple. I know I saw one on a Rheem 90 that was only about 10 years old.

 

problem solved.. replaced the smart valve ... i had 2 pins stuck together on the smart valve.. thanks everyone

 

I caught a SV a few weeks ago in an older furnace. Guy said he googled it and figured out how to jiggle the molex plug at the valve and make it work. Yep - it's failing and it's expensive to replace it. You would be best served with a new complete system. Done.

So I looked on Utube to see what he was talking about and saw a disturbing video detailing a DIY repair involving removing the valve, disassembling it and soldering wires on to the circuit board contacts to get around that notorious issue.

You'd think they'd at least warn you to turn the gas off first.

 

Sometimes, especially with a SV it's ok/faster to be a parts changer, I ain't to proud. :grin2:

 

Is it a 90%, if so is the flu blocked at all?

 

Hmmmm. Why is the inducer running all the time even when tstat dropped out? Its not the smart valve. Trace your wires back and see where they lead you and problem will be at end of your finger tips. Sit and think for a sec

 

Why is the inducer running all the time even when tstat dropped out? Its not the smart valve.

When a call for heat is made by the thermostat, the ST9160 will verify the safety circuit and then sends a control voltage (24volt) signal to the SmartValve to start the inducer motor and ignition sequence.
Pin #2 on the SmartValve for the inducer motor 4 pin connection is always HOT(120v) when the door switch is closed.
Once the signal from the ST9160 is received to start the inducer motor, a relay inside the valve will close sending line voltage back out Pin #1 to start the inducer motor.
Pins #3 and #4 on this 4 pin connector are neutral. Bottom line - replace the Smart Valve.

Some smart valves power the inducer to, if the relay in the valve is stuck closed, the inducer will run continuously. :grin2:

 

From what i've seen after looking at the online manual. THe smart valve doesn't even need a board to operate! A transformer, t-stat and a fan delay relay would do.:grin2:

 

From what i've seen after looking at the online manual. The smart valve doesn't even need a board to operate! A transformer, t-stat and a fan delay relay would do.:grin2:

Wished you would have told that to the idiot that invented them many years ago. :grin2: