Gas Furnace Problem

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  #1  
Old 11-23-02, 08:20 PM
brokenfurnace
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Exclamation Heater Won't Fire When Temperature Cold.

I HAVE NO HEAT IN THE HOUSE FOR 5 NIGHTS, PLEASE HELP!!

I have a Carrier Unit (Electricity for cooling and gas for heating) 10 years old. This year when the weather get cold, I turn the unit on and something weird is going on for the last five days.
Every day, from 11:00AM to about 6:00PM, the unit is working fine because the attic is hot. From 6:00PM to 11:00AM next day, the unit can not turn on because the attic get cold. I have spent a lot of time watching it and here is what I see : when temperature is hot in the attic ( from 11:00AM to 6:00PM )I turn the unit on, the ignitor is on and gas get fired right away. But when the temperature get colder (from 6:00PM to 11:00AM next day) when I turn the unit on, the ignitor is on for about 15 seconds then off and gas can not fired. The ignitor is on then off about four times then the system shut up completely for couple hours. I have replaced both the FLAME SENSOR and HOT SURFACE FURNACE IGNITOR , but the problem is still the same.
Anything else can be wrong? Maybe the control board is bad?
PLEASE HELP. I DO NOT HAVE HEAT FOR THE LAST FIVE NIGHTS. WEATHER IS NOT TOO BAD SO FAR BUT IT WILL BE COLDER VERY SOON.
Thank you for your help in advance.
 
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  #2  
Old 11-24-02, 05:19 AM
ServiceGrunt
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There are several posibilities. Your gas valve could be bad, your burners or burner orfices could be plugged, ignitor could be out of place(to far from gas flow), pressure switch or inducer fan could be causing problems. Better get a pro over there. Just not a DIY project. Too many possibilities.
 
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Old 11-24-02, 05:41 AM
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I agree

a tech to check things out is a must, you may have a bad heat exchanger and the air is cooling off the signal, I take it this is a direct ignition (no pilot ). to see if its getting signal you need to measure voltage on the gas valve terminals to see if your getting 24VAC, if not, the board could be bad especially is it is trying to start.. there are so many possibilities. with cold weather and a DIY forum, I wouldn't wait too long, if pipes freeze, your a penny wise and a pound foolish...
 
  #4  
Old 11-24-02, 07:21 AM
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Hello brokenfurnace. Welcome to the Heating & Cooling forum & our Do-It-Yourself Web Site.

Personally, I do not understand how plugged orifices could be the problem, since you are caliming the burners are firing up when the attic temp is warm. Nor could I see why a firebox [heat exchanger} would be the problem. Just my opinion and personal observations based soely on the information you posted.

I would be more inclined to think there is a problem with the gas valve or some problem within the wiring or low voltage circuitry.

Cool, cold or damp conditions increase the resistance to electrical flow. Therefore, any higher then normal resistance may not be providing enough current flow to the gas valve to allow the solenoid to open during cold conditions.

Same can apply to the circuity and other related componets. Especially if the heater has a induction power venting system. Moisture in the system can cause like or similar conditions.

Specific problems happen to different models. Depending upon the exact model of unit you have may provide & determine the problem and correctional solutions. A professional heating agent for that brand may be required to resolve this type of problem.

If you need further assistance or can provide additional specific detailed information regarding the heater, please use the REPLY button to add it and or ask additional questions.

Regards & Good Luck, Forum Host & Multiple Topic Moderator.
TCB4U2B2B Company Enterprises. Energy Conservation Consultant & Gas Appliance Diagnostics Technician.
 
  #5  
Old 11-24-02, 08:50 AM
brokenfurnace
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Hello there,
I would like to thank all of you who take time to read and respond to my problem.
Here is my additional question: If there is any problem with wiring / low voltage circuitry / pressure swith / inducer fan / fire box (heat exchanger), what can I do to fix the problem? I try to fix it myself first before I call a pro over. I know it is very expensive when a pro knocks at your door, and ONLY GOD KNOWS what he does and how much he will charge me.
My neigbour had a same problem with her heater, I came over and fixed it, and it is working fine. Now I can not fix my own unit!!
It bothers me alot. She offered me $100.00 for 2 hours I worked on her unit. I did not take her money simply because I am not a pro and she is my neighbor. I have spent almost $100.00 on my unit and still have no heat at night.

My Product # 58RAV075---101JC
Model #58RAV075-JC
Series # 100

Please help me if you have any idea.

Regards,

Brokenfurnace

P.S. I am really broke!! Got laid-off over a year and still looking for a job!

Thanks again for your help.
 
  #6  
Old 11-24-02, 10:59 AM
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Basics

Lets start off with some preliminary tests.
Do you have 24VAC to the gas valve when it attempts to fire?
 
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Old 11-24-02, 11:03 AM
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Wink also..

Look at some of the test procedures I wrote to Sheri E on her has furnace problem
 
  #8  
Old 11-24-02, 11:06 AM
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sequence of operations

appears to end at gas valve opening. as 01453 suggested, see if 24 volts is present at valve at any time between when the hot surface ignitor glows, and when it cuts off. if so, bad valve, if not, very possibly the circuit board. have seen this before during cold weather, almost like the board itself expands and contracts, opening or closing the circuit at will.
 
  #9  
Old 11-24-02, 11:18 AM
rclhvac
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What model furnace are we talking about- 80% or 90%
 
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Old 11-24-02, 11:18 AM
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connections....

Make sure all your connections are clean and tight. Many times this cause may be due to a loose or corroded/oxidized connection in the circuit.
 
  #11  
Old 11-24-02, 02:38 PM
brokenfurnace
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Dear [email protected],

Thank you for your response.

I got your response and I follow the way you wrote to Sheri E about her furnace problem.
I took the thermostat from the wall. I took all wires off from the thermostat then I connect only the RED and WHITE together. The heater operates right away, heat coming out very good like nothing is wrong with the unit. So the thermostat is BAD and I need to replace thermostat ONLY. But like I said in the very first thread, now is 4:30 CT ( my time ) the attic is hot so the heater is working fine. I do not know it will work later at night when the attic get colder or not. I hope that the thermostat is only thing bad in my unit.
I appreciate your help very much and I will try to help others whenever I can, the same way you are helping people right now.
Keep up you good work.

Thanks again.

Brokenfurnace.
 
  #12  
Old 11-24-02, 10:12 PM
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GOOD NEWS...

KEEP US POSTED, WERE ALL CURIOUS!
 
  #13  
Old 11-25-02, 08:09 AM
brokenfurnace
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NOT TOO GOOD.....

Dear HVAC01453

It was not too good!!
I tested the unit when the attic was warm. The unit seemed OK, but around 7:00 PM, unit could not turn on, I tried one more time. Only RED and WHITE connected together, the unit went thru the cycle 4 times then the system shut down completely. It means the thermostat is not BAD. Today, I will give the unit one last try : I will clean up all the connectors inside the unit like you wrote to Sheri E. If it is still bad then I have no choice but a pro.
Anything else can you think of? I am really do not want to call a pro, simply because I am broke.
Any advice can you give me? Please help.
Thanks for your time. I am waiting to hear from you.

Brokenfurnace.
 
  #14  
Old 11-25-02, 08:51 AM
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Broken,

what type of furnace do you have?? 90% (PVC pipe for venting) or 80%??

What state are you in?? How cold is cold attic?? ALso when you say hot attic?? How hot is that?? SOunds like you have a very large swing in temp in your attic.

If it is a 90% and the attic is reaching freezing point, your drains and/or pipes might be freezing up, and it might be causing your presser swich to trip since it can't drain or exhaust..

Check your pressure swich and see if your getting 24 volts across the swich when it trips..
 
  #15  
Old 11-25-02, 09:29 AM
brokenfurnace
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Reply from Broken.

Hi Jay11J,

Thank you for your quick response,

I am not a HVAC so some terminology I do not understand.
You asked me what type of furnace I have, 90% or 80%? I do not know what does it mean.
I am sure my attic is never reaching freezing point. I am in TX, and when I say my attic cold, I mean temp is about 55 F to 65 F.
and hot is about above 70 F. I have a big electric fan installed on the roof and it turns on and off by itself.
I also do not know how to check the pressure swich. Can you tell me where it is in my unit and how to check it. It is Carrier unit and model # is 58RAV075-JC. Series # is 100.

I am waiting to here from you.
Thanks in advance.
Broken.
 
  #16  
Old 11-25-02, 10:26 AM
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difficult

Its difficult to explain testing procedures to someone that has no idea what the terms are. You may be loosing gas pressure for one reason or another. without testing tools its a guess at best.
 
  #17  
Old 11-25-02, 03:11 PM
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Ignitor...

I believe you have a unit similar to the 58MXA Carrier. If so, the hot surface ignitor (HSI) should be checked. With the power off, pull the plastic plug connector apart and OHM the ignitor at room temperature ( during the warm attic temp time or remove it) and it should read between 45 and 90 OHMS a resistance over 110 ohms indicates a cracked element and will not be hot enough to ignite the gas. Visually checking the HSI ignitor. Any whiteish areas are cracks. This is what is normally replaced, on a gas unit any time ignition fails. Because its a new one, doesn't mean it is good. Some guys have these bouncing around in their trucks all summer long. I believe you have a fault code light also. Ig nition failure is 34. 3 long flashes and 4 short, or vice-versa. Oh use a flash light and check to see if critters/birds are blocking the exhaust or intake are vents when this fails to fire. Put your meter on the two terminals of the inducer air switch, this is a pancake shaped silver disc below the gas valve. You should read 00.00volts the gas valve terminals should read 24volt(+/- 4volts ). The ignitor heats up for 17 seconds and energizes main gas for 5 seconds and an additional 2 seconds to prove flame is this happening, at the end of 5 seconds the ignitor is de-energized. Bottom line...I think your going to find the ignitor bad.
 
  #18  
Old 12-01-02, 10:34 AM
brokenfurnace
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The control board was bad.

Finally I gave up. I call a pro over. He came. He tested the unit and he by-passed the pressure switch. The control board was bad. He replaced the board and my unit is working fine since. The board is too expensive but it is worthy. On the night my unit was fixed, temperature in my area went down to 38F, the very first night cold of this season.
Good luck to all.
Broken.
 
  #19  
Old 12-01-02, 07:03 PM
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confused....

If the board was bad.....why would the pressure switch need to be bypassed? This is a safety! This is an air flow proving SAFETY switch. I hope this isn't still jumped out!
 
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