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Discussion Starter · #1 ·
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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Discussion Starter · #2 ·
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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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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Discussion Starter · #4 ·
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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Thanks for responding to the post!

I'm hoping there is a board fuse and that it's fried.1

Outside of that, I'm not sure which is less expensive, A step down transformer or a board.2

Question:

If I transformer goes bad does it take out other parts as it goes?3

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

Richard
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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Discussion Starter · #7 ·
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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Discussion Starter · #9 ·
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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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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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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Discussion Starter · #13 ·
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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Discussion Starter · #15 ·
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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Discussion Starter · #16 ·
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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Discussion Starter · #17 ·
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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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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Discussion Starter · #19 ·
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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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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