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Billy
Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19512
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a TRANE BLU055E936B1 Gas Fired Air Furnace. My heat

Customer Question

I have a TRANE BLU055E936B1 Gas Fired Air Furnace. My heat stopped blowing last night. The Thermostat is working properly. The gas in on and pilot is ignited. I removed the fan blower door and manually pressed the blower door switch. The switch clicks and ignited the furnace once, but once I released it that time, it would not re-ignite. Is this most likely a failure with the door switch or something more? This happened in late fall but I assumed the door switched had slipped under the door frame, once I played with it a couple of times it ignited the furnace and has worked until last night.
Submitted: 4 years ago.
Category: HVAC
Expert:  Billy replied 4 years ago.

You are correct. I also commend you for realizing and recognizing the function of door switch. If it becomes too troublesome you can bypass until you get a new switch.

 

Obviously it is a safety feature for when the bottom door is removed to cut power.

 

I wish you luck

Customer: replied 4 years ago.
I have bypassed the blower door switch. Should the furnace ignite imediately? Furnace has not ignited now for well over an hour. What should I do next? Tranformer? Gas Valve 36C03 Type 222? Clean pilot ignition?
Expert:  Billy replied 4 years ago.

I apologize...computer troubles...

 

Clean all the rods and metal components of ignitor with steel wool, reset power and see if cycle improves

Customer: replied 4 years ago.
I was able to wire brush the thermocouple senser using a small brass brush. I lit the pilot and turned the system on. The pilot is burning just fine. Still no gas released to the burners though. Does this mean I need to replace the gas valve or is there more to check? Is the thermocouple causing the problem? If pilot is lit, thermocouple is working properly, no?
Expert:  Billy replied 4 years ago.
Customer: replied 4 years ago.
No. Looks like this one and connects directly to the top of the Gas Valve 36C03 type 222.

http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=PIL2400&Category_Code=P

Expert:  Billy replied 4 years ago.
This valve has 2 terminals under the thermocouple fitting that run to a safety. Follow the 2 wires from under tcouple fitting and tell me what they run to.
Customer: replied 4 years ago.
The wires run to what looks like a sensor into the sheet metal. I removed it and it has a copper loop on the end. The plate reads General Electric and 415º with a long part no.
Expert:  Billy replied 4 years ago.
Remove the wires from it and touch them together
Customer: replied 4 years ago.
Do you mean to remove the wires from the terminals and cross connect the terminals with say a screw driver?
Expert:  Billy replied 4 years ago.
that works also
Customer: replied 4 years ago.
I removed the wires from the terminals. The pilot went out, immediately. I touched a screwdriver to both terminals connecting them and had no reaction.
Expert:  Billy replied 4 years ago.

 

Good, at least now we know the limit and thermocouple are good. Do you have a meter to check 24v at the gas valve?

Customer: replied 4 years ago.
No. no voltage meter. Once I have one what should I do? I will run and buy another, I'm sure my stepson or ex-wife has mine.
Expert:  Billy replied 4 years ago.

you will check for 24 to the gas valve terminal...one meter lead to ground and the other to th on valve.

 

24v on th with no burner = bad gas valve

Customer: replied 4 years ago.
I performed the meter reading. Make sure I did this properly. I placed the black (-) lead to the body of the gas valve and the red (+) lead to the th terminal (left of center terminal). I used ACV setting of 50 on the GB instruments GMT -312. This is a needled meter not digital. Should have purchased digital. The needle moved and held slightly at 2 marks off 0 (zero). I want to say that's definitely less than 24. Note, I did not lite the pilot, nor did I replace the two wires to the terminals removed a step or two ago.
Expert:  Billy replied 4 years ago.

 

sorry for delay...my regular job needed my attention.

 

Now take the blower door off and tape the switch down again. Find the white wire coming from the thermostat and tell me what it goes to in the furnace.

Customer: replied 4 years ago.
I believe I made a mistake when metering the Gas Valve. I changed my placement of the black lead and placed it into the black wire wire-nut connecting the power to the furnace and the red (+) lead to the th terminal (left of center terminal). The meter read 24 when I metered it in those locations. Doing this wrong? When I placed the black on the ground wire coming into the furnace and then the red to the th terminal it read maybe 5-10.

The white wire from thermostat? Is the the white wire running with 4 others green, red, yellow and blue?
Expert:  Billy replied 4 years ago.
correct, the white with the colors you described. Does it run through the limit?
Customer: replied 4 years ago.
It connects by wire-nut to a heavier wire with inline fuse to the th terminal on the gas valve.
Expert:  Billy replied 4 years ago.

 

Great, that is what I wanted....now put red lead to TH and black lead to cabinet while thermostat is calling for heat.

Customer: replied 4 years ago.
Do I first remove white wire from th? Black wire to cabinet? Cabinet meaning the furnace itself?
Expert:  Billy replied 4 years ago.
Leave white to TH and black meter lead to furnace cabinet
Customer: replied 4 years ago.
Meter needle is barely moving to 5 - 10
Expert:  Billy replied 4 years ago.

lets leave the black lead on the side metal of the gas valve, no paint and conductive.

 

Now move the red lead to the white wire coming from stat. Unhook from wire nut and test the wire direct.

Customer: replied 4 years ago.
The meter read maybe 15.
Expert:  Billy replied 4 years ago.

 

go to thermostat and remove top section. Take R wire and W wire and twist together. Metal to metal.

Customer: replied 4 years ago.
Done. So far nothing happening. It's been about 5 minutes
Expert:  Billy replied 4 years ago.
Take apart red and white and put a meter lead on each wire
Customer: replied 4 years ago.
Done. Almost nothing maybe 5.
Expert:  Billy replied 4 years ago.

 

we need to bypass the door switch and make sure power is going to furnace. The red wire should have 24 volts at all times. We are missing power somewhere

Customer: replied 4 years ago.
Done. Bypassed the door switch. What next? read red and white wire at thermostat again?
Expert:  Billy replied 4 years ago.
Correct
Customer: replied 4 years ago.
Done. when I place the black meter lead on white and Red on red or vice versa the meter reads barely anything. When I place the black to the black ground and and red to red the meter reads a tad more than 25V. Sorry I do not work with electricity often or even some.
Expert:  Billy replied 4 years ago.

Now hook all back up.

 

so red wire to ground got us 24v. Pull the TH wire from gas valve and measure it to ground the same way. I know we did this before but it was missing last time

Customer: replied 4 years ago.
My apologies. The one step back. It was not a black wire at the thermostat is was a green wire. It's connection on the thermostat is marked with a G and there is black electrical tape close to the end.

I re-connected the thermostat. I took the th wire from the gas valve and touched the black lead to the galvanized metal cabinet and red lead to th, resulting in low meter reading. I then touched the black lead to the incoming ground wire, (black, white, ground - power source) and red to th, resulting in the same. I then touched the same thermostat green wire and red lead to th, resulting in 24V.

Gotta call it a night. How do I resume tomorrow?
Expert:  Billy replied 4 years ago.

Ok now that your familiar with the meter a bit more....

 

all the thermostat wires come into the furnace. Do they all just connect to other wires or do any mount on a control board?

Customer: replied 4 years ago.
They connect to other wires. I have two groups of wires coming into the unit other than the main power supply wire. One from the thermostat and I don't know about the other.

Once connected by wire-nuts to other wires some connect to post of terminals (see photos)

graphic

1st group
Colors are red, yellow, lt blue, white and green.
yellow not used

2nd group
Colors are dark blue, white and red.
dark blue not used

graphic

some sort cylinder connected to this, hard to see in photo.






Expert:  Billy replied 4 years ago.

 

excellent, the cable with 5 wires comes from thermostat, the cabel with 2 wires goes out to the outdoor ac unit.

 

The white wire in the cable with 2 wires is know as common. The red takes 24v out to the ac unit.

 

The white wire in the 5 wire cable is the one that goes to the gas valve on TH right?



Edited by Billy on 1/12/2010 at 4:18 PM EST
Customer: replied 4 years ago.
Yes
Expert:  Billy replied 4 years ago.

 

Great, thermosta hooked up, heat turned up, power on. Remove TH wire from gas valve. take wire nut off the white wire in the 2 wire cable but leave twisted together.

 

Red meter lead to TH wire removed from gas valve and black lead to white wire in 2 wire cable.

Customer: replied 4 years ago.
Sorry for the delay. I did what you instructed and the needle did not move at all.

Expert:  Billy replied 4 years ago.
that means no power is getting to the valve. Can you see if 24 v is at the red wire in 5 wire cable
Customer: replied 4 years ago.
Black lead to Red Wire and Red Lead to th terminal?
Expert:  Billy replied 4 years ago.
Sorry, black lead to the 2 wire cable white. Red lead to red wire
Customer: replied 4 years ago.
Yes, 24V
Expert:  Billy replied 4 years ago.

 

And not to beat a dead horse...but the white wire from the thermostat goes direct to TH on gas valve?

Customer: replied 4 years ago.
Yes, however it is connected by wire nut to another white wire connected by wire nut to another white wire with and inline fuse connected to th.
Expert:  Billy replied 4 years ago.

 

I understand...check the inline fuse

Customer: replied 4 years ago.
Looks to be okay when shining light through opposite side, I don't see any breaks, but there is some amber discoloration to one end of the fuse. The fuse looks like this one.

http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=FUS0283&Category_Code=F
Expert:  Billy replied 4 years ago.

 

Take the fuse section out of the equation and have white wire go direct to TH.

Customer: replied 4 years ago.
OMG...Burner came on immediately
Expert:  Billy replied 4 years ago.
Excellent, gosh I am glad you have patience!
Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19512
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Billy and 5 other HVAC Specialists are ready to help you
Customer: replied 4 years ago.
Thanks very much. You know I have a friend that works does this stuff for a living, some 25 years now, but he is always working late and I decided I wanted to learn a little something. Thanks for your patience. Have a great week.
Expert:  Billy replied 4 years ago.

 

Well done. I thank you

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