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I have a Reznor CUAU 400furnace that will not light. The 24vac transformer was bad, replaced but furnace will not light

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Possible voltage spike took out your transformer and might have taken out something else? don-ohio

Posted on Dec 31, 2016

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1 Answer

REZNOR KEEPS SHORT CYCLING,IS IT THE THERMOSTAT?


Probably not. It has an overheat safety that is probably telling the controls it is getting too hot. check/replace high limit switch

Feb 14, 2015 | Reznor Hanging Furnaces-Power Vented-...

Tip

Basic Furnace or Heating System Troubleshooting


If you are not getting any response from your furnace and your furnace is not working, then the first thing you want to check is that there is power coming in.

If you have 120VAC coming in, then check to see if you have 24VAC coming from the transformer. If you do not have the 24VAC from the low voltage transformer then the transformer has burnt out. Power surges and especially brown outs (low voltage) can cause the transformer to burn out.

If there is 24VAC coming from the transformer secondary then check to see if there is a fuse in the low voltage circuit. Sometimes the fuse on the circuit board and often are an automotive type fuse that plugs into the circuit board. Sometimes the fuse will be an inline fuse that will be in a black round tube type holder. If the fuse is blown do not replace with a higher amperage fuse, you will cause more damage, or blow the transformer.

If the fuse is blown then unhook the t-stat wires and check again. This will tell you if the short that blows the fuse is external to the furnace or internal.

Now if all of that checks out then the next thing would be to check the low voltage safety circuit. Things such as door switches and high limit switches are all possibly included in this circuit, if any of them are open the heating system will not work.

As a last resort, the problem could be in the circuit board. They do go bad and can shut everything down also. Most circuit boards will also flash a LED light to give you a code for what is wrong and why the furnace is not working.
Count the number of flashes and then check the inside of the front cover to see what the code represents.

This will give you a basic progression of things that you can check through. Using an electrical meter is essential to being able to diagnose and troubleshoot the heating system. If you do not have one and/or do not know how to use an electric meter proficiently, then find someone to help you that does know how to use one well to help you.

on Oct 29, 2010 | Heating & Cooling

1 Answer

Fan comes on no heat


turn a/c power off. place a jumper wire between both sides of switch, leaving wire attached on both sides. power on, set thermo to heat, if furnace stay lit after test, replace rollout switch. If furnace shuts down after short time it's not the rollout. please remove jumper after test.

Feb 12, 2015 | Reznor Hanging Furnaces-Power Vented-...

1 Answer

My white rogers f189 11 thermostat is off- nothing is lit up?


Remove the cover from the thermostat and check for voltage (usually 24VAC) on the red "R" wire. It comes from the transformer at or in the furnace. Place one probe on the screw marked "R" and the other probe to any of the other wires coming into the thermostat. Depending on how old and the type of system you have, you may have a black wire (Common or neutral), green (fan), yellow (cooling call) and white (heating call). Heat pumps and staged system will have more wires and other colors. If there is power at the thermostat, check that all connections are tight and you have a fresh battery installed if it has one. If it still does not work, replace the thermostst. If there is no power at the thermostat, check for power at the furnace. There should be a disconnect switch near the furnace, it may or may not be fused. Check with a voltmeter to see that you have power at the disconnect first and that any fuses are good. If it is ok, move on to the transformer at the furnace. Check the "Line" side of the transformer for 120VAC power and the "Load" side of the transformer for 24VAC power. If it is ok, and you have no power at the thermostat, the wires to the thermostat are bad or you have a loose connect at one end or the other.

Jan 10, 2015 | Heating & Cooling

1 Answer

I am wiring a Honeywell wifi unit and I used a separate 24v transformer and connected to the c and rc terminal. My system is ac and heat and uses both and rc and rh wire. I wired the rc to the r ter


A thermostat is a switch. It connects 24vac from one terminal to another depending on the request. The 24vac comes from a transformer, usually located in the furnace and connects to the R terminal. Since you are using RH and RC without a jumper between it means there are two transformers, one in the furnace for heating (RH) and one in the air conditioner condenser used for cooling (RC).
Your old thermostat was probably mechanical and did not have a C (24vac common) terminal. Your new thermostat requires power to operate therefore needs a wire connected to a C terminal. I would get rid of the transformer you added and look for an unused wire in the bunch at the thermostat. If it's there connect it to C on the thermostat and to C on the furnace. Remove any jumper from R to RC or from RH to RC depending on your thermostat and connect wires same as the old thermostat.

Jul 04, 2014 | Heating & Cooling

1 Answer

I have ducted airconditioning in my home and the programmable thermostat is completely blank and the whole system is not turning on, could you please help me in trying to troubleshoot this matter...Thank...


Hi,
The transformer or fuse is blown... check the circuit board for a fuse and then check the transformer for 24vac...



Here is a tip that will help you try to figure out why your furnace is not working.

Basic Furnace or Heating System Troubleshooting

heatman101


Jan 15, 2011 | Carrier Heating & Cooling

1 Answer

No heat no fan whatcan i check


Hi,
If you are not getting any response from your furnace then the first thing you want to check is that there is power coming in.
If you have 120VAC coming in then check to see if you have 24VAC coming from the transformer. If you do not have the 24VAC from the transformer then the transformer has burnt out. Power surges and especially brown outs can cause the transformer to burn out.
If there is 24VAC coming from the transformer then check to see if there is a fuse in the low voltage circuit. Sometimes these are on the circuit board and often are an automotive type fuse that plugs into the circuit board. If it is blown do not replace with a higher amperage fuse, you will cause more damage, or blow the transformer. Sometimes the fuse will be an inline fuse that will be in a black round tube type holder.
Now if all of that checks out then the next thing would be to check the low voltage safety circuit. Things such as door switches and high limit switches are all possibly included in this, if any of them are open the system will not work.
As a last resort, the problem could be in the circuit board. They do go bad and can shut everything down also.

This will give you a progression of things that you can check through. Using an electrical meter is essential to being able to diagnose and troubleshoot the system. If you do not have one and/or do not know how to use one proficiently, then find someone to help you that does know how to use one well to help you.

heatman101

Oct 28, 2010 | Heating & Cooling

1 Answer

I have a Goodman GMP075-3. Worked OK on A/C.


I come across this one a lot. You need to switch the wires at power cord.
  1. Pull power out
  2. follow the cord* back to the furnace
  3. Open the front door
  4. There should be a small metal box where the cord leads to inside the furnace
  5. Open that up
  6. Take the electrical tape off
  7. Pay attention to which wire goes where
  8. Switch the two wires around
If you still got problems ill walk you through it over the phone www.fastacservice.com

Oct 12, 2009 | Goodman Heating & Cooling

2 Answers

24v wiring for RHEEM heat pump


Brown wire connect to com C on terminal block in your furnance (0VAC from 24VAC transformer)
Yellow turn on compresor (hot wire from 24VAC Transfrormer)
Blue switch Valve from AC to Heat (hot wire from 24VAC Transfrormer)
Purple prevent starting compressor in Heat pump and furnace in same time

Jul 02, 2009 | Ruud UBHC Air Conditioner

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