# Lennox G20 Series - Bad blower board - or is it more?



## inn8pwr (Jul 13, 2009)

Hi all,

New to the forum. Old hat DYI'er.

History: 

While running AC the system reached temp and shut off correctly (presumed). Then it simply refused to start. I wanted a new thermostat anyway (for energy savings reasons) so I bought one and things started and worked fine ... for two days. Big smile.

Again, the system would not initiate. Opening the access to the HVAC blower et al. I found water. "Not good," I'm thinking! I end up blowing backward on the consensor line and immediately was rewarded with a quart of water. AT this point I believe I solved the water problem. Now, what has been the result of the water was my next task. I found the water skirted all system wire points yet possible pooled in the bottom item .. The air cleaner control box?? Still not sure, haven't opened it up. I went after the blower et. al. first.

Following the Lennox Flow chart provided I jumped wires (r & G, R & Y, etc) to learn that all systems (AC, blower, heat) would run (except the air cleaner lights didn't come on). However I could not successfully jump the wires at the Thermostat side. So indeed, a bad wire was found that had rubbed open near sheet metal. It is certainly worth mentioning that the wire did have water on it. I believe the water finalized the "shorts" in the system. But leading to a bad original thermostat??? Maybe the original thermostat wasn't bad. No worries, wanted a new one anyway.

I replaced the wire AND the thermostat again. It ran fine for a week. Yesterday it died again; or didn't start as the case is. I do doubt the air cleaner has been working. I'm not sure it ever has since I bought the house in 2003.

Current:

I DO have power going INTO the Blower circuit board (BCC2) and the "current" does get past the switch to the board. However. I am UNABLE to jump R&G etc and get running parts. It appears current isn't getting through the board. This is confirmed by the Lennox flow chart which reveals that I need a new Blower circuit board. An internet search revealed that I require the 48K98 (48K9801, 48K98-LB) as it replaces all BCC1-3 older boards such as mine.

Questons:

1. Do I need a board?

2. What have I missed? I'd hate to get the board only to plug it in and have it blow again. Is there another item I should know to check??

3. Could the Air cleaner box be creating any feedback blowing out a blower board?

Thanks for reading and responding. The item is in excess of $100 and I'd hate to buy a part only to plug it in again and watch it fry.

By the way. After finding water I did place a large fan to blow on the HVAC for a day. A near 100 degree day.

Thanks again,

Richard


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## inn8pwr (Jul 13, 2009)

*More data*

I see lots have viewed this posting. Hopefully someone will reply.

Here's what else I've learned.

Tonight when I go home I'll look for a fuse on the Circuit board but I doubt it has one. If the fuse is bad, replace and hopefully smile.

I'll also check for continuity at the 24 volt side of the board to see if one of my transformers may be the problem. There is no current at them.

So it's looking like one of three things:

1. Fuse - please
2. Transformer
3. Board

It's starting to look less like a board????

We'll see.

Any advice?

Richard


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## Yoyizit (Jul 11, 2008)

See if there are test points (TP1, TP4, whatever) on the board. Then see if the manuf. will tell you what voltages you should be seeing on those points. I doubt they will give you a board schematic, and it would be of limited use anyway.

If you post the system schematic then the impedance looking into each connection that goes off the board can be calculated and if all are OK then the board, in theory, should not blow out.

This might take a while.


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## inn8pwr (Jul 13, 2009)

*Board Testing*

Thanks for responding to the post!

I'll see what depth my manual has when I get home tonight. Hopefully my meter is worth a darn too.

I'm hoping there is a board fuse and that it's fried.

Outside of that, I'm not sure which is less expensive, A step down transformer or a board.

Question:

If I transformer goes bad does it take out other parts as it goes? Could it be a transformer AND the fuse?

Looks like I'll be getting familiar with the schematic soon enough.

Richard


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## Yoyizit (Jul 11, 2008)

inn8pwr said:


> Thanks for responding to the post!
> 
> I'm hoping there is a board fuse and that it's fried.*1*
> 
> ...


1 That is just one possible beginning indicator
2 The board may be 10x to 20x the cost of a 'former.
3 upstream parts, usually.


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## hvaclover (Oct 2, 2008)

Trans don't normally go bad with out cause, Chances are you have a blown fuse.


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## inn8pwr (Jul 13, 2009)

*No Fuse*

No fuse present. At least not on the board.

What now Mr. Wizards???

I'll likely take the board off and look for board issues. I'm starting to doubt that I'll find any.

This DIY'er is about to call for help... beyond this forum. Dern, they just charge to show up.

Thanks for continued help. Please show me which path to follow.

Richard


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## hvaclover (Oct 2, 2008)

You ;;;,p,;


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## inn8pwr (Jul 13, 2009)

*Help*

Not quite sure what to make of your last posting.

I am still attempting to DYI, just not getting anywhere.

Latest find was NO on board fuse.

Continued problem: no current on the 24 volt side of the board.

Likely problem?? Perhaps my water problem effected the transformer??

I have been active attempting to locate a circuit board should it come to that. I've sent my make and model number to a parts house that is looking it up.

I'll atempt to examine the board as well.

But I am still asking this forum what the best course of action is??

I suppose I need to learn how to test a transformer.

Thanks for reading and responding, ...... constructively.

Richard


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## Yoyizit (Jul 11, 2008)

inn8pwr said:


> Continued problem: no current on the 24 volt side of the board.


I guess you mean no voltage. If you have a clamp-on ammeter you could check if the 'former secondary is shorted by something on the board, which means the secondary current should be quite a few amps and the 'former won't last much longer.
Also check that the 'former primary is getting its rated voltage, probably 120v.

A 'former with an open circuited secondary should read ~27v. It reads 24v when it's loaded down with its rated current. A 40 VA 'former would have a rated current of 40/24 = ~1.7A.

Post a photo of the board.


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## SKIP4661 (Dec 3, 2008)

You won't find a fuse on that G-20. However if you look around the outside of the electrical box you should find a little square black and white button. This is a resettable breaker that is used instead of a fuse. If it is tripped you have shorted the stat wires somewhere.


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## hvaclover (Oct 2, 2008)

That's what I was trying to remember. 

Damn WhisperHeat.


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## inn8pwr (Jul 13, 2009)

*Fuse vairiant - Transformer bad - Board???*

Hi all,

Thanks Skip, you are correct, there is no on board fuse. At the site you suggested I did previous fine a seperate switch with a screw-in type glass topped fuse. The fuse remains fine and I do have 120V going into the board.

However, I have found that I do not have 24V coming out of the Transformer. The 24V side is "open" and I just brought home a replacement one.

Prior to installing and powering up I'm in a hunt to find the cause of the Transformer blow-up?? I have chased the line to the AC and fine it free of fraying.

Not sure what to do now and am considering hooking it all up and see how long the transformer works.

So here's the question:

Would a problem on the board cause a transformer to blow???

If so, I suppose I'd better test the board as previously posted, or replace the board.

Would a bad board blow a transformer??

Thanks,

Richard


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## Yoyizit (Jul 11, 2008)

Fuse the secondary of your new 'former.
For 40 VA at 24v you could use 40/24 = ~1.5A slow blow.


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## inn8pwr (Jul 13, 2009)

*Fuse the secondary?*

Nice.

So are these in line fuses??

BTW:

I went ahead and put her back together and the house is cooling as we speak.

Thanks for the help. Looks like I can avoid the expense of a blower board for now.

I will look into the 40V/24V inline fuses.... if you meant inline.

Thanks,

Richard


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## inn8pwr (Jul 13, 2009)

*fuse rating??*

ABout the fuse:

My secondary side is 24V.

is the 40V/24V inline fuse the one I ask for??

Not quite sure what I'm supposed to be getting here.

Took me a while to understant what 'former meant.

Not as "old Hat" as I thought.

Richard


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## inn8pwr (Jul 13, 2009)

*Fuse the secondary?*

Ok,

The secondary side of the transformer says 24V 30VA. That seems high for such a little Circuit blower board?? ...or is VA different from amps??

I'm finally getting IT here. So, 40VA/24V. Sorry, I'm a bit slow (too - Dracula reference).

I was at the hardware store and the locals told me to get an amp rating and come on back. Only they didn't have a method for placing the fuse in-line.

The local auto parts store does have in-line fuses. Thick wires. Before I wire nut a 40 amp fuse to each of the two 24 lines I think I'll call my local appliance part store and ask for the correct fuse and methodology for installation. I am assuming the fuse goes between the board and the 'former. Please correct me if I'm wrong. Does it have to be BOTH 24v lines exiting the 'former??

Yup, ignorant. (Keep your fangs to your self Dracula)

Thanks for your upcoming advise. Almost there!

Really, Thanks a ton!

Richard


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## Plumber101 (Feb 25, 2009)

Go back to the auto store and ask for a spade inline fuse with 14 or 16 agw. Install it in the 24 vac circuit off the transformer before it goes to the board.

For the fuse just usa a automotive 3 amp and you will be fine


Most board of the day will have either a 3 or 5 amp fuse. I use 3 amp. I buy the inline fuse adapter at radio shack and the fuses at an automotive store in bulk.


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## inn8pwr (Jul 13, 2009)

*Fuse the secondary? Con't*

Thanks Plumber,

So it sounds like Just one of the two wires coming out needs to get fused???????

Yoyizit, is the "40/24 = ~1.5A slow blow" A better choice?

I'm mostly learning here now as I realize that either solution is better than the "lack of fuse" I currently have.

It was 97 outside today, thanks guys for getting me this far. The house is a single level and is cooling off nicely! I'll wait til tomorrow to finalize this restoration.

So again, fuse 1 line or both 24V lines?????

Respectfully submitted,

Richard


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## Plumber101 (Feb 25, 2009)

One line.

Also need to figure out which is power and ground of the transformer and install in the power side.

1.5 slow is OK but the 3 amp will do the same thing. Then if it blowes in the middle of the night your car may have a spare.

Just remember this KISS

K - Keep
I - It
S - Simple
S - Stupid

Sometimes it does get more complicated but with this just keep it simple.

Round fuse are not very common and can be hard to find sometimes


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## hvaclover (Oct 2, 2008)

If he replaced the transformer with an OEM he will need to know which color is hot because Lennox transformers of that vintage do not show a reading from 24 v hot to ground because the way they wound the primary and secondary.


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## Plumber101 (Feb 25, 2009)

Clover

Could he use a DVOM and from one lead go to one of the secondary wire and the other lead go to the transformer block

I have never encountered this tansformer you talk of.


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## hvaclover (Oct 2, 2008)

Plumber101 said:


> Clover
> 
> Could he use a DVOM and from one lead go to one of the secondary wire and the other lead go to the transformer block
> 
> I have never encountered this tansformer you talk of.


Don't know. Never tried that.But if it works it will tell which is hot. I just made sure I had 24v across the secondary and made sure I had the color right. But if he changed it and got a standard transformer it won't make any difference,


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## inn8pwr (Jul 13, 2009)

*Fuse the secondary? Con't*

Oh guys,

Ignorance lead me to a NON-OEM transformer at my local Appliance parts store. I'm thinking, :A transformer is a transformer."

Well, Did I get lucky???? It is running. But.....

So, I bought a class 2 40VA transformer PRI 120V SEC 24V.

So, if it is non-lennox will there be a reading... now. So am I looking for one side to show voltage and one to not??

While I'm a firm believer in the KISS menatality, I'm starting to feel like I'm fixing something that ain't broke. None-the-less, I do INTEND to get a fuse their to prevent future woes! Provided I can figure out what's best.

So, check for voltage and fuse one side?

Richard


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## Plumber101 (Feb 25, 2009)

So am I looking for one side to show voltage and one to not??

True

And put the fuse in the one that shows voltage


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## hvaclover (Oct 2, 2008)

Plumber101 said:


> So am I looking for one side to show voltage and one to not??
> 
> True
> 
> And put the fuse in the one that shows voltage



Yeah you're ok. That OEM was just another way lennox keeps everybody in the dark about about the true specs on their parts.

They sell a motor that says 3/4 hp on it and it really is almost or is a full horsepower.


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## Yoyizit (Jul 11, 2008)

inn8pwr said:


> Nice.
> 
> So are these in line fuses??
> 
> ...


http://www.rd.com/images/tfhimport/2003/20030701_Fast_Auto_Fixes_page003img003_size2.jpg
So all it was was an open 'former secondary winding? You got away lucky.

I guess if you fuse the primary 120v winding then both windings and the upstream wiring are protected. 40VA/120v = 1/3A.


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## hvaclover (Oct 2, 2008)

Yoyizit said:


> 40VA was just an example. Fuse it depending on the 'former rating.
> http://www.rd.com/images/tfhimport/2003/20030701_Fast_Auto_Fixes_page003img003_size2.jpg
> So all it was was an open 'former secondary winding? You got away lucky.



He ain't outta the dark yet. He's gotta find out why it blew.


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## inn8pwr (Jul 13, 2009)

*Why it blew - exactly!*

I am hoping the reason it blew was the water leak down the thermostat wire etc.

I'm hoping that all water residue is gone.

However, the fact that the system worked for 1 week and then DIED AFTER I solved the water problem is still mystery. A weakened 'former decidedd to kick the bucket on it's own time?? 

The system has always RAN fine once on, it just WON'T start a new cycle when prompted by the thermostat (historiclly speaking here - read the full thread for detail).

FYI: My old thermostat was a 4 wire and the new thermostat accommodates the system fine - with 4 wires.

All wire connections to AC and internals look fine (what's visualized easily). The thermostat wire is new.

Actually, I need to get the electronic air cleaner working. I imagine that would be good for the seasonal allergens in the air??? I'll bet it's the power supply in that puppy that died.... perhaps another thread??

I'll get to the Transformer fuse tomorrow and let you know what I find!

Thanks for all the help, and for speaking in Lay-persons terms.

Hmmmm, I wonder if there is a circuit that spikes when the thermostat tells the system to turn off????????????? Wish I had the fuse on there now!

Thanks again,

Richard


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## hvaclover (Oct 2, 2008)

inn8pwr said:


> I am hoping the reason it blew was the water leak down the thermostat wire etc.
> 
> I'm hoping that all water residue is gone.
> 
> ...



The most common reason for blown transformers is homosexual electrons:whistling2:


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## Yoyizit (Jul 11, 2008)

inn8pwr said:


> I am hoping the reason it blew was the water leak down the thermostat wire etc.
> 
> I'm hoping that all water residue is gone.
> 
> ...


If the system continues to work for X weeks you will decide it is fixed. Based on the recent past, what value would you use for X?


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## hvaclover (Oct 2, 2008)

Yoyizit said:


> If the system continues to work for X weeks you will decide it is fixed. Based on the recent past, what value would you use for X?


Pi r 2?


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## Yoyizit (Jul 11, 2008)

hvaclover said:


> Pi r 2?


Old joke: What is the square root of 69?


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## hvaclover (Oct 2, 2008)

Yoyizit said:


> Old joke: What is the square root of 69?


Lickety-split:huh:?


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## Yoyizit (Jul 11, 2008)

hvaclover said:


> Lickety-split:huh:?


Eight something. :laughing:


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## inn8pwr (Jul 13, 2009)

*Transformer die - why*

While I question the accuracy of your tag-line (and perhaps electron preference): 

I would like to know what the most common reasons for a burned transformer are??

Thanks All,

Richard

Ps. Dracula, have you ever heard of V:tES (VTES, Jyhad - 1994 name)?


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## hvaclover (Oct 2, 2008)

inn8pwr said:


> While I question the accuracy of your tag-line (and perhaps electron preference):
> 
> I would like to know what the most common reasons for a burned transformer are??
> 
> ...



OOOhhh boy...too numerous too mention but it just might be the magnetic coil on your ac contactor or a spot rubbed bare on the stat cable to your ac.


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## inn8pwr (Jul 13, 2009)

*The "X" Factor*

I'm getting these posts out of sequence ....

As for the X factor: Bummer. I hear you saying the pup is on it's way out?The definition of X I want and what those with experience anicipate from a 1989 unit are possibly two different things ... is my worry. So, you tell me. What should I expect?

Better yet,

What else do I need to do to make this puppy last a couple more seasons???

Old joke: What do you call a Roman with a hiar between his teeth?


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## Yoyizit (Jul 11, 2008)

inn8pwr said:


> As for the X factor
> What else do I need to do to make this puppy last a couple more seasons???


Things with coils are inherently hardy, but. . .

Heat ruins a 'former and heat comes from current flow and if it's abnormally high [like from an overload or short circuit] or the ambient temp. is very high, the 'former life will be very short.

With fusing you are taking a reasonable precaution to protect your new 'former. You could use an inline fuse or find a place to mount a fuse holder.

With the value of X:
if your 'former failed every week, and then lasted 4 consecutive weeks without failing I'd say the root cause is fixed, so X = 4.
If your 'former failed once/yr, and then lasted 2 or 3 consecutive yrs without failing I'd say it's fixed, so then X = 2 or 3.

BTW, if it's the custom in HVAC circuitry to fuse the secondary, then I'd follow the custom.


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## inn8pwr (Jul 13, 2009)

*"X" Factor - Thanks for filling in the blanks*

I'll get the fuse set up today. 

Regarding heat, the region the 'former is in is a bit tight. Not sure how to deal with that without working with sheet metal.

BTW: That is one incredible Photo (profile image). I think I'd get out of the water! Wow.

The unit does seem to be responding normally. I'll likely chime in a couple more times; certainly until the fuse is set.

Thanks,

Richard


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## Yoyizit (Jul 11, 2008)

inn8pwr said:


> Regarding heat, the region the 'former is in is a bit tight. Not sure how to deal with that without working with sheet metal.


With the price of some control boards, if you had failures traced back to excessive heat it might be worthwhile to mount a small $5 computer fan to blow air over the board.
Hosfelt.com has these.

So what do you call that Roman?


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## inn8pwr (Jul 13, 2009)

*Almost forgot -*

Joke: Gladiator


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## inn8pwr (Jul 13, 2009)

*Fan Over Blower Circuit Board*

I have thought about putting a fan over the board as you suggest. I happen to have an extra case fan and an extra video card lying around somewhere.

Should I draw power from the 120V side or the 24V side? I suppose I could crack a computer case and find out quick enough.

Richard


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## Yoyizit (Jul 11, 2008)

If you add a fan to a gas furnace you may have to put in baffles to avoid disturbing the flame.


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## inn8pwr (Jul 13, 2009)

*Fan Over Blower Circuit Board*

I've elected to NOT go with the fan. I'll be adding the fuse tonight. Decided to ge with the 3 amp inline.


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## Plumber101 (Feb 25, 2009)

Keep going like this Inn8 and you'll go pro


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## psilliman001 (Sep 1, 2007)

*hey!!...*



hvaclover said:


> The most common reason for blown transformers is homosexual electrons:whistling2:


lets watch that p c stuff the aclu monitors this website:laughing::no:..........Jack


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## hvaclover (Oct 2, 2008)

psilliman001 said:


> lets watch that p c stuff the aclu monitors this website:laughing::no:..........Jack


They are the second most common reaon...


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## buglas (Dec 30, 2009)

*Good call on the fuse*

I had to replace the BCC2 board in my G20. Burnt relay, scorch marks, etc. - no question about replacement. Nothing worked after installing. After reading here, I identified the unmarked electrical box and found the fuse to be blown. Upon replacement, all is well. BTW, there was a spare fuse taped to the inside of the e-box cover. 

Thanks, all.


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