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jrloar
jrloar, HVAC Technician
Category: HVAC
Satisfied Customers: 292
Experience:  Electrician for 12 years, every HVAC certification available
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i have a conquest 90 natural gas furnace, the flame was blocked

Resolved Question:

i have a conquest 90 natural gas furnace, the flame was blocked from reaching the flame sensor, now the blower and draft fan run continuously, i shut the power off to it for over 2 hours and as soon as i turned it back on both the draft fan and blower fan turned back on. i need to reset the system but only found one roll out switch. i pushed it and it did nothing.
Submitted: 2 years ago.
Category: HVAC
Expert:  jrloar replied 2 years ago.

jrloar :

Hello, my name is Jim. I am looking forward to helping you solve your problem today.

jrloar :

give ma a few minuets to look up your system

Customer:

ok

jrloar :

on your controle board you should have a model number can you give that to me

jrloar :

it is a Honeywell, Utec, or a Johnson

Customer:

model number is XXXXX

Customer:

honeywell

jrloar :

can you tell me if it looks like this? Terminals as well?

jrloar :

https://www.rheemote.net/docstore/webdocs/Public/ServicePublic/Trouble2a/pdfs/Wiring/1401.pdf

Customer:

for the most part yes it has some variances to that diagram

jrloar :

i am trying to locate the correct one

jrloar :

https://www.rheemote.net/docstore/webdocs/Public/ServicePublic/Trouble2a/pdfs/Wiring/1399b.pdf

jrloar :

does this one?

Customer:

nope, thats not it either

Customer:

is there a model number on the actual board?

jrloar :

should be

Customer:

where about would it be located and what number codes would i be looking for?

jrloar :

it can be any where on the board and can be any series of numbers and or letters

jrloar :

does yours have a 9 wire plug on it?

Customer:

yes

jrloar :

square?

Customer:

yes

jrloar :

we may be able to work it with tis info

jrloar :

do you have a short piece of wire you can use as a jumper

Customer:

yes

jrloar :

every thing I tell you to jump out is only 24 volt but please be careful not to touch any thing else.

jrloar :

the black and white on the board is 120 volt

Customer:

ok

jrloar :

you should have a RED wire and a RED/WHITE wire

jrloar :

Red with white stripe

jrloar :

Jump these two and turn it on

jrloar :

see if it runs like it was

Customer:

no red with white strip wire

jrloar :

hmmm

jrloar :

is the plug numbered

jrloar :

or on the board?

jrloar :

1 threw 9

Customer:

nope

jrloar :

can you tell me the colors?

Customer:

i'll upload a pic of the board and the plug

jrloar :

that would be great

Customer:

http://s1271.photobucket.com/albums/jj629/tweeter22525/?action=view&current=IMG-20120309-000401.jpg

Customer:

ok i uploaded a pic of the board

jrloar :

from what I see you have 2 reds the same and one darker red?

jrloar :

could be considered purple?

jrloar :

do you have a multimeter

Customer:

yes

jrloar :

yes to the multimeter

Customer:

sorry, yes to the multimeter

jrloar :

do you know how to use it

Customer:

yes

jrloar :

turn off the power, unplug the 9 wire plug and check continuity between the two red wires

Customer:

nothing registering

Customer:

i checked between all the reds and all were open

jrloar :

ok try it this way. plug it in, turn on the furnace, carefully jump between the two red wires with the jumper and your furnace should turn off then...

Customer:

ok

jrloar :

let me know whet it does and if when you remove the wire it should restart

Customer:

just to clarify what two red wires?

jrloar :

YES

jrloar :

on the plug

jrloar :

the 9 pin plug

Customer:

center top and bottom right

jrloar :

yes

Customer:

that just shuts off the draft fan, blower still runs

jrloar :

what blower is running?

Customer:

the main forced air blower

jrloar :

does it run with the 9 pin terminal unpluged

Customer:

yes both the draft fan and the main blower run with it unplugged

jrloar :

I am working on it

Customer:

i'm not going anywhere, too cold to move at the moment, lol

jrloar :

one thing you can do while I am working on a salutation is to trace the 2 red wires and find what all the terminate to. When you find them all jump them out with the furnace on one at a time to see what one is causing the draft blower to run one of the temp limit switches are open in that circuit and see if one of the conections have more than just 2 red wires terminating at it

jrloar :

So if it is cold then the furnace will not even light?

jrloar :

and how was the flame blocked from the flame sensor

Customer:

no, what happened was corrosion was blocking the flame travel across the burners, so it wouldn't jump to ignite the 4 burners , it caused it to go in safe mode and just the draft fan and the blower will run now. it won't even attempt to open the gas switch to ignite or even turn on the glow plug

jrloar :

OK you have a red and yellow labled Xformer

jrloar :

actualy xfmr

jrloar :

unplug one of those and turn on the furnace

Customer:

unplugged the yellow common and got just a buzzing sound

jrloar :

but the fan never ran?

Customer:

no, nothing ran

jrloar :

that is a good thing

jrloar :

trace the two red wires and jump out the safeties it terminates to one at a time while it is running

jrloar :

you should have up to 4 devices it will terminate to

Customer:

i have 2 it runs to, one is a round switch with a button top, and the other is a flat fiber board

jrloar :

did you jump both one at a time

Customer:

jumped one at a time to both of them, draft fan and blower still runs

jrloar :

that does not make since you jumped the board red to red and the draft stooped corect.

Customer:

yes

jrloar :

make sure your Thermostat fan is on auto

Customer:

thermostat is set to auto and set to call for heat at 72 deg. current temp is 62

jrloar :

can you shut the heat off and try it

Customer:

yes

Customer:

heat set to off, both fans kicked on, jumped both points and both fans still run

jrloar :

is it possible to jump both that the reds run to at the same time

Customer:

yup

Customer:

same result

jrloar :

then there has to be a nother circuit in it

jrloar :

I see to the right of the picture you sent me it has a wiring diagram can you send post a pic of that?

Customer:

thats the trouble shooting guide

jrloar :

ok

Customer:

the only other circuit is the air pressure switch for the draft fan. i just jumped that and still the same result

jrloar :

it is looking more and more like a bad board

jrloar :

https://www.rheemote.net/docstore/webdocs/Public/ServicePublic/Trouble2a/pdfs/Gas_Furnace/Wiring/90-24007-04-07.pdf

jrloar :

this is the basik diagram

jrloar :

slightly different but the same

Customer:

it worked fine till the flame didn't jump, once it went into safe mode it wouldn't reset

jrloar :

that is why I am saying your bord has failed

jrloar :

What we done SHOULD have solved shut it off

jrloar :

We bypassed every safety it has

Customer:

i'd just hate to throw parts at it and hope it fixes it

Customer:

i'm sure the boards are not cheap

jrloar :

no they are not... BUT you have nothing left to do... We jumped out every senser and it still does not work. This means it is NOT a safety

Customer:

well i guess if i have to dump money into it, might as well put a whole new furnace in, at least that way i got a 10 yr warranty with it, lol.

jrloar :

I can look at a price for a board if you want

Customer:

yeah wouldn't hurt to see what it would cost

jrloar :

http://www.climatedoctors.com/items/item.aspx?itemid=429740

Customer:

that's not too bad

jrloar :

now thats not a direct replacement but will work

jrloar :

direct replacement is close to $250

Customer:

either way i will have to invest something into it, i will have to weigh out my options and figure out the best route to go. thank you for the help

jrloar :

http://www.climatedoctors.com/Items/hone309?&caSKU=hone309&caTitle=Honeywell%20ST9120U1011%20Control%20Circuit%20Board%20Fan%20Timer

jrloar :

that one will also work

jrloar :

Let me know if you do get a control board and I would be happy to help you get it working.

Customer:

will do, thank you again.

jrloar :

I will be on here after 4 tomorrow if you want to try it again...

jrloar :

we can remove every thing and start from scratch. I would do that now but I get up for work in 6 hours

Customer:

i hear ya, time to fire up the fire place and get a few drinks in me to keep warm. feels like deer camp all over again! lol

jrloar :

would you want to try that after 4

jrloar :

basicly jump every thing at the board. bypass every thing

jrloar :

then IF it does fire up hook it up one at a time

Customer:

i might i've already taken up alot of your time as it is. if i decide to do it i will let you know and we will go from there.

jrloar :

if I did not enjoy it I would not be on here now.. Trust me we do not get paid enough

Customer:

lol, yeah i see that, well i'll let you go then, if i want to try and take another crack at it i will let you know. what time zone are you in?

jrloar :

E

jrloar :

I am in PA

Customer:

ok, i'm in michigan. same time zone then, i'll let you know if i want to take another crack at it.

jrloar :

ok keep warm

Customer:

will do, got my hunting overalls out and a fire going, guess i will have to cuddle up to the ol lady for once,lol, have a good night and thanks for the help again.

jrloar :

any time

jrloar, HVAC Technician
Category: HVAC
Satisfied Customers: 292
Experience: Electrician for 12 years, every HVAC certification available
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