Need a couple of Relays for a Lennox Control Board

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Old 08-09-10, 03:49 PM
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Need a couple of Relays for a Lennox Control Board

Hi all,

Does anyone have a couple of relays I could get my hands on for the control board in a Lennox G26 furnace?

The relay I need is an NAIS, part number AJS131281. I need two of these, to replace K2 and K3.

Additional info stamped on the relay is JS1-B-24V, and SPULE 24V. there are also two waveforms shown; one is a solid line, the second is three dashed lines directly under the solid line. (assuming those refer to steady state and pulsed, or a square wave....)


I found a distributor in NJ who has these relays, but they have a minimum order of $250, and the only place I'd been able to find in about 2 days of calling around. My local Radio Shack and local HVAC companies, electronics suppliers and so on don't have these.

My option is to get the retrofit PC board kit (83M00) for the G26 but even that is $189 (best price locally but with support if I need it, $139 online with no support).

Being out of work for the past 3 years has put a dent in the budget, so I'd like to replace these two relays first and fix the problem with the blower circuit that way if possible.

Thanks!


(For those curious, the blower comes on when the thermostat is switched to furnace position, but not when the unit is switched to cooling position. I "hotwired" the circuit so the blower runs all the time, while the A/C still cycles, but momma is after me to get this thing fixed, lol.)
 
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Old 08-09-10, 08:57 PM
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If this is an electronic t'stat, have you checked the back of the t'stat to make sure the selector switch is on gas and not electric??
 
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Old 08-10-10, 05:24 AM
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Hi mbk3,

Thanks for getting back to me.

It is an electronic t-stat, a Honeywell programmable unit (I didn't pull it off the wall to get the model number; I've had it a dozen or so years.)

The Lennox G26 had been working just fine for many years prior to this problem occuring this spring. When I flipped the the selector switch on the front of the t-stat (under the flip down door)from heat to cool the blower would not run, but the condenser outside did.

I'm not sure how the gas / electric switch you mention would affect this, since it had not been changed, nor had I ever seen it (or looked for it, frankly). I replaced the batteries in the t-stat earlier this winter while still using heat (February?), just like I do about once a year or so.

Any further thoughts, or where I can get those relays would be appeciated!
 
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Old 08-10-10, 06:30 PM
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The reason I asked, with the selector set on "elec" the fan comes on when furnace calls for heat. No delay
 
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Old 08-12-10, 02:09 PM
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Replace the board. The board is not designed to be repaired.


Also, there are a lot of different systems on the board. Replacing the board renews all of them and greatly increases the likelihood of reliable service from the furnace for years to come.
 
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Old 08-12-10, 02:37 PM
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Originally Posted by SeattlePioneer View Post
Replace the board. The board is not designed to be repaired.


Also, there are a lot of different systems on the board. Replacing the board renews all of them and greatly increases the likelihood of reliable service from the furnace for years to come.
Not designed to be repaired... really? I can see the solder points for the relay on the underside, and back in the day, that IS how we fixed electronics. We carried an o-scope along with components, as well as tools and meters, and repaired to the component level. Since the component is not an SMD (surface mounted device), pray tell why it can't be repaired?

The other systems? They don't need to be renewed, they work just fine.

Here's the deal... I've been out of work for three years, and know how to repair the board. I can either fix it for $10-15 and use the money for other necessities, or pay $189 to "renew" systems that are working just fine.

Thanks for the advice, but you'll understand if I keep trying for the relays...
 
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Old 08-12-10, 06:16 PM
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Since you seem to know at least a little about electronics I would suggest that you check Allied Electronics for the relays. Their print catalog is an 8x10 format and they have about 90 pages of relays. They have no minimum purchase requirements and I have used them often with complete satisfaction.

http://www.alliedelec.com/

Or you could perhaps use a more generic relay such as the plug-in models from Potter and Brumfield with connecting wires from the circuit board.
 
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Old 08-14-10, 08:46 AM
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How do you know that the relays are bad? There could be another problem with the board.
 
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Old 08-14-10, 09:20 AM
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Originally Posted by Muggle View Post
How do you know that the relays are bad? There could be another problem with the board.
I went through the circuit diagram myself, and a second time with a friend who is more current (no pun intended) with electronics as a result of his work.

The K2 and K3 relay contacts are directly what feed power to the motor windings via the ACB Cool and ACB Heat spade connections on the circuit board. (Ref. the circuit diagram for the G26 control board).

Given the way the two relays are in the circuit (n/c contact of K2 feeding n/c contact of K3) there is a possibility that the problem is with one relay or the other.

The blower motor works when the thermostat is set to HEAT, and the blower motor also works runs when the t-stat auto/on switch is set to ON, so it's pretty much down to the two relay contacts that provide power to the windings of the blower motor when the A/C is switched on. (The A/C winding also works, because I rewired that as a test also...)

Given that they are relatively simple to replace, I was going to unsolder and replace both, and be done with it. My bet is still on K3 being defective, however.

My next step may just be to unsolder the K3 relay, and take it to Radio Shack to see if they have an equivalent relay; after operating power requirements (24VDC), the real issue is finding a relay in that size, with the right number of pins.

Easy stuff... Now, if I could just find those darned relays!
 
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Old 08-14-10, 09:24 AM
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Originally Posted by furd View Post
Since you seem to know at least a little about electronics I would suggest that you check Allied Electronics for the relays. Their print catalog is an 8x10 format and they have about 90 pages of relays. They have no minimum purchase requirements and I have used them often with complete satisfaction.

http://www.alliedelec.com/

Or you could perhaps use a more generic relay such as the plug-in models from Potter and Brumfield with connecting wires from the circuit board.
@ Furd

Hi, and thanks for the suggestion on Allied. I went to their site and did a search. They do not carry NAIS products at all, and nothing came up for part number AJS131281. Trying the number alone without the AJS in the prefix came up with an unrelated part altogether.

I do appreciate your post and trying to help, however!

mowerman
 
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Old 08-14-10, 10:44 AM
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It is extremely unlikely that you need an exact duplicate down to the same manufacturer. I suggest first determining the "action" of the original relays, SPST, DPDT, 3PDT or whatever and also the external dimensions contact rating and coil voltage and then searching for an equivalent relay. Pin-out is pretty much standardized among all manufacturers so that shouldn't be a problem.

The other thing I suggested, soldering flexible wires to the board in place of the existing relays and then running those wires to a separately mounted relay is still a viable option. P&B plug-in relays (or equivalent) are usually available for around $15 and another $5 for the socket. It wouldn't be a pretty repair but it would work.
 
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Old 08-14-10, 11:24 AM
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Originally Posted by furd View Post
It is extremely unlikely that you need an exact duplicate down to the same manufacturer. I suggest first determining the "action" of the original relays, SPST, DPDT, 3PDT or whatever and also the external dimensions contact rating and coil voltage and then searching for an equivalent relay. Pin-out is pretty much standardized among all manufacturers so that shouldn't be a problem.

The other thing I suggested, soldering flexible wires to the board in place of the existing relays and then running those wires to a separately mounted relay is still a viable option. P&B plug-in relays (or equivalent) are usually available for around $15 and another $5 for the socket. It wouldn't be a pretty repair but it would work.

Thanks again, Furd!

My friend and I also thought about using Potter Brumfield or simiilar in a socket, and running wires to the PCB. Like you said, not pretty, but would work. My concern was once the covers were reassembled whether I would need to be concerned about any of the connections shorting to the frame and etc., as well as where to physically let this relay dangle and etc.

I don't know the configuration of the relay, just the numbers on them, and cannot locate any cross reference charts either. Given the application I might venture a guess it is SPST, but that's only my guess.


Like you said, they are pretty much the same in any given category, and is why I thought I might try the "can you match anything up to this?" route at the local Radio Shack.

Thank you for the continuing information and consideration on your part,

mowerman
 
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Old 08-14-10, 11:34 AM
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Quite honestly, I wouldn't go to RS for anything more complicated than a battery, but that's just me.

If you can take take one of the relays to an industrial supply house you might have better luck. Grainger is one that comes to mind and they have stores in many major cities. Although they are primarily a wholesale concern they do sell to cash customers.

Grainger
 
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Old 08-16-10, 03:59 PM
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The board does more than control the fan relays. It also controls the combustion air fan motor, gas valve etc. How do you know one of these systems is not compromised by the bad board? Trying to hot wire a furnace board is not safe and could cause carbon monoxide in the home. If an HVAC tech or the gas company has to come out this winter to work on the system and they see a hacked up control board they will condemn the system and shut the gas off to it. It's not worth putting your family at risk. Get a new board from the local company and have them install it and confirm that the system is operating in a safe manner. I understand times are tough but a furnace isn't something to take shortcuts on.
 
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Old 08-16-10, 06:20 PM
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Nobody has suggested "hot wiring" the control board and I doubt that the original poster has even considered it. What he wants to do is to replace some malfunctioning relays. He even wants to do it with original equipment relays. I don't find that at all dangerous IF he knows enough to properly solder the new relays without creating solder bridges on the printed circuit board.

Also, it is NOT that the board is made in a manner that repair is impossible but that the cost of labor to repair a board is likely to approach the cost of the new board. There is also the FACT that the majority of furnace technicians do NOT have the tools or expertise to do board repairs.

I've worked with electronics all my life and I wouldn't hesitate for a minute to repair a circuit board. I also had a very successful career in design, installation and operation of large fuel-fired boilers and furnaces and understand completely the sequence of operation and safety controls.


Mowerman, if you can post the schematic I can probably tell you what action you need in the relays. If you can post a picture of the board I may have some more suggestions.
 
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Old 08-16-10, 06:35 PM
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Originally Posted by furd View Post
Nobody has suggested "hot wiring" the control board and I doubt that the original poster has even considered it. What he wants to do is to replace some malfunctioning relays. He even wants to do it with original equipment relays. I don't find that at all dangerous IF he knows enough to properly solder the new relays without creating solder bridges on the printed circuit board.

Also, it is NOT that the board is made in a manner that repair is impossible but that the cost of labor to repair a board is likely to approach the cost of the new board. There is also the FACT that the majority of furnace technicians do NOT have the tools or expertise to do board repairs.

I've worked with electronics all my life and I wouldn't hesitate for a minute to repair a circuit board. I also had a very successful career in design, installation and operation of large fuel-fired boilers and furnaces and understand completely the sequence of operation and safety controls.


Mowerman, if you can post the schematic I can probably tell you what action you need in the relays. If you can post a picture of the board I may have some more suggestions.
There would be no way of knowing if other systems of the board are compromised. It's not worth the risk.
 
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Old 08-16-10, 07:07 PM
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Of course there are! Or don't you do standard safety checks after working on a furnace?
 
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Old 08-16-10, 08:24 PM
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Originally Posted by furd View Post
Of course there are! Or don't you do standard safety checks after working on a furnace?
Yes I do. And I'm also able to sleep at night after I've done one.
 
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Old 08-17-10, 05:44 AM
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I sleep well too...

Originally Posted by jeggs View Post
Yes I do. And I'm also able to sleep at night after I've done one.
Thanks for the concern Jeggs. Like Furd, I too have considerable experience in these areas. My technician days were in industrial automation, working on 480 3 phase, hydraulics up to 2250 psi, waterjet systems up to 50,000 psi, and then on the opposite end of the scale, more delicate work including component level board repair (yes, I do know how to solder without creating bridges).

Any work I did that was not focused on safety, proper procedures, application requirements and accepted industry practices would result in the possibility of serious injury or death, either to myself or to others who would be in promixity of equipment once I was done working on it.

Your protestations are a bit over the top. When I replace the components the board, except for the "varnish" placed on the board by the original manufacturer the repair will be undetectable, certainly so from the component side of the board, and certainly will not be noticed by (most of) today's technicians who are only trained in component replacement and not component level repair. Nothing will be "hacked up", and nothing will be done as a "short cut" other than to repair what is failed, nothing more and nothing less. We don't replace an entire car if a transmission goes bad. There are some who can do the work and some who cannot, and philosophically, that's all I'm trying to do here.

I sleep well at night too, except that now I wonder if your posts are from a manufacturer or service company, trying to continue to promote the idea that all repairs can only be done by factory authorized service. That said, if I had a problem with the condensor or a TVX valve for instance, I "would" call for service... I know my strengths, and play into those, but don't get involved in areas I have no knowledge of. Thanks for your concern, however.

mowerman
 

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Old 08-17-10, 06:01 AM
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Furd; info on drawing

Originally Posted by furd View Post

I've worked with electronics all my life and I wouldn't hesitate for a minute to repair a circuit board. I also had a very successful career in design, installation and operation of large fuel-fired boilers and furnaces and understand completely the sequence of operation and safety controls.

Mowerman, if you can post the schematic I can probably tell you what action you need in the relays. If you can post a picture of the board I may have some more suggestions.
Thanks Furd,

I could not attach the drawing, but the G26 service manual found at the attached link has the schematic of the surelight control board on page 38.

http://www.acfurnaceparts.com/Service%20Manuals/G26.pdf

I'll look forward to your reply after you take a look at this. Appreciate your continued efforts to try to help!

Mowerman
 
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Old 08-17-10, 10:12 AM
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Originally Posted by mowerman556 View Post
Thanks for the concern Jeggs. Like Furd, I too have considerable experience in these areas. My technician days were in industrial automation, working on 480 3 phase, hydraulics up to 2250 psi, waterjet systems up to 50,000 psi, and then on the opposite end of the scale, more delicate work including component level board repair (yes, I do know how to solder without creating bridges).

Any work I did that was not focused on safety, proper procedures, application requirements and accepted industry practices would result in the possibility of serious injury or death, either to myself or to others who would be in promixity of equipment once I was done working on it.

Your protestations are a bit over the top. When I replace the components the board, except for the "varnish" placed on the board by the original manufacturer the repair will be undetectable, certainly so from the component side of the board, and certainly will not be noticed by (most of) today's technicians who are only trained in component replacement and not component level repair. Nothing will be "hacked up", and nothing will be done as a "short cut" other than to repair what is failed, nothing more and nothing less. We don't replace an entire car if a transmission goes bad. There are some who can do the work and some who cannot, and philosophically, that's all I'm trying to do here.

I sleep well at night too, except that now I wonder if your posts are from a manufacturer or service company, trying to continue to promote the idea that all repairs can only be done by factory authorized service. That said, if I had a problem with the condensor or a TVX valve for instance, I "would" call for service... I know my strengths, and play into those, but don't get involved in areas I have no knowledge of. Thanks for your concern, however.

mowerman
I am not affiliated with any manufacturer or service company. And if the board has an IC logic chip my concerns are not over the top.
 
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Old 08-17-10, 12:03 PM
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Originally Posted by jeggs View Post
I am not affiliated with any manufacturer or service company. And if the board has an IC logic chip my concerns are not over the top.
Thanks for that clarification, and for letting me know your additional concern; it is appreciated. The board, as I recall it consists of all passive components, and there is no IC logic chip, at least not in the proximity of the K2 and K3 relays. I wouldn't be putting that much heat into the board to affect a neighboring IC, and use proper board handling procedures.

Thanks again for your concerns!
 
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