[TXN TOM]

After two days of a burning smell, our furnace failed. The control board was charred, and I picked up a universal board to replace it. ( our very unreliable HVAC guy called Sat morning and allowed to let me pick up the universal board.). The new board didn't have the correct wiring for our older furnace, but all the controls, etc, shown on the new diagram are on the old diagram. Since the univ board calls for separate Hi Limit Output (Hi Lim) and Roll out Switches(RO), and the original circuit had Hi Lim and RO in series, I separated them by making a new loop for RO and reconnected the Hi Lim to the original connector to mate with the 12 pin connector. (To do this I removed wires from the additional harnesses supplied w the kit and added splices to get all the components in their respective places.) I also added a univ. flame sensor to the circuit, positioned it to be in the flame, as well.

After troubleshooting the flashing codes - first polarity, then RO open, I verified connections, removed the RO wires, jumpered them, and, while the flashing light goes to solid, meaning Normal operation, still no joy. It appears everything is wired properly, but, hey, stuff happens, and I must be overlooking something. On my way to pick up two new RO sensors. BTW, the univ board is a White Rodgers 50M56U-843.

 

[ben's plumbing]

how old is the furnace....I think if its before 1992 don't think that board will work....one of my techs had the same problem with a rheem furnace and he had to get another board...not sure though...ben sr

 

[TXN TOM]

Ruud per-94 furnace fixed!

Well, if you look at my previous post, you'll see that I had an older furnace and a new control board. Big problem turned out to be the Rollout switches, which I just finished replacing. Along with that, I formed a bracket and added a universal flame detector.

Doing it by myself probably saved me $400 or more, as the board alone from Ruud is about $220 plus tax.


As I'm an engineer, I've been around Molex connectors for years, and I knew how to remove the pins and plugs from the connector body. Doing so, I fashioned a hybrid harness to fit the Ruud furnace, which required me to break the series connected Hi Limit and Rollout switches into two separate circuits, which were then added to the harness. Also added a flame detector to the centrally located pin 14 on the board.


Yeah, it took me some 14 hours to troubleshoot and figure it all out, but once done, the furnace is running perfectly. If I were to do this again on a similar furnace, it would take an hour or less...


Let me know if any of you need a diagram of what the reworked harness looks like.

 

[yuri]

You said you added a universal flame sensor. What did it have B4 or what was wrong with the original one. Hopefully you put it EXACTLY in the correct position or same positions as B4 as a flame sensor is a critical safety device and you cannot just stick it in the flame anywhere. It should be by the furthest away burner from the igniter and must respond with 2 seconds if there is no ignition or you could get one awful flashback/delayed ignition if it does not do its job properly and the gas pressure is low etc etc. Not somethng you want to fool around with for some serious liability and safety reasons. Post a closeup pic of it with good lighting and we may be able to see if it looks safe.

 

[TXN TOM]

Thanks, Yuri

Yuri,

Great point to make about the position of the flame sensor. After reading your post, I moved the sensor farther away from the igniter, actually as far as it will go.


The previous controller didn't use a flame sensor, and there were no instructions available with The one i picked up. Just the plastic bag it came in.


You are correct about the two seconds, as prior to having the sensor in the flame, the system would ignite, and immediately shut down. The position of the sensor has the tip roughly 1/4 in. Into the flame, and while it's doing its job, it's not getting red hot. Let me know if it needs to be red hot, and I can adjust the position. It's mounted to a 1/32 thk bracket made of 304 Stainless, and bolted to the sides of the flame unit. If I can get pics from the phone and post them I will.


The new board makes a world of difference in the house, as I now suspect several issues with soft failure of the RO switches or possibly an intermittent somewhere in the system.


Thanks for your help.

 

[JScotty]

Yuri,

Great point to make about the position of the flame sensor. After reading your post, I moved the sensor farther away from the igniter, actually as far as it will go.


The previous controller didn't use a flame sensor, and there were no instructions available with The one i picked up. Just the plastic bag it came in.


You are correct about the two seconds, as prior to having the sensor in the flame, the system would ignite, and immediately shut down. The position of the sensor has the tip roughly 1/4 in. Into the flame, and while it's doing its job, it's not getting red hot. Let me know if it needs to be red hot, and I can adjust the position. It's mounted to a 1/32 thk bracket made of 304 Stainless, and bolted to the sides of the flame unit. If I can get pics from the phone and post them I will.


The new board makes a world of difference in the house, as I now suspect several issues with soft failure of the RO switches or possibly an intermittent somewhere in the system.


Thanks for your help.

So you're saying your furnace had an ignitor but didn't have aflame sensor? I've never seen that before. Not sure how that could safely do that.

As for the flames sensor I'm sure it's a "flame rectification" system. It basically passes ac voltage through the flame causing it to switch to dc voltage. The board senses dc voltage off the case and is it sees dc voltage it knows a flame is present.

The temperature of the sensor doesn't matter. Just that the voltage passes through the flame and into the burner.

 

[beenthere]

Old board used the HSI as the flame sensor.

 

[JScotty]

Old board used the HSI as the flame sensor.

Ahh I've never ran into one of those, but I have heard of them.

I must say I'm pretty impressed, that sounds like it would've been a difficult install even for a pro. Well played TXN TOM :thumbsup:

 

[Doc Holliday]

A pro would not ever re-wire a board to accommodate it not being the correct one. You void any and all warranty as well as assume all financial responsibility for when that home burns to the ground.

Not saying what he did was not intriguing, just not smart.

 

[yuri]

Ruud/Rheem and Coleman had that system of using the HSI as a flame sensor and it is pretty much obsolete. Both of them have a factory approved conversion kit with the board and sensor and bracket which is what the Pros use.

 

[JScotty]

A pro would not ever re-wire a board to accommodate it not being the correct one. You void any and all warranty as well as assume all financial responsibility for when that home burns to the ground.

Not saying what he did was not intriguing, just not smart.

It's not the wrong board it's a universal board. And I work in the field and we install universal boards sometimes. Granted I'd check to make sure all the limits actually work etc, but it's not unsafe to use a part that isn't a direct manufacturers replacement.

 

[Doc Holliday]

are you kidding me? I've worked in the field for going on 13 years now, yuri for who knows how many hundreds of years . The conversion kit design specific for his unit is the only one that should have been used but alas, the HO was wanting cheap.

Your belief of one single board being universal to every furnace out there is corrupt and dead wrong. If you think, which apparently you do, that re-wiring a universal board to makeshift the conversion kit is correct than I need your companies phone number, you need to find a different field to work in.

so what's that number?

 

[yuri]

Chill Doc.

We do use universal boards and they are NOT universal. They cover about 80% of the models and Lennox especially is not a good candidate for them. The main issue being that a Pro knows the sequence of operation and how to properly test the safety controls but a DIYer does not. I avoid universal boards like the plague as they have all kinds of quirks and the manufacturers OEM board is always much better. In a pinch they are useful but you need to carefully read the cross reference chart that WR and HWell supplies and even with a S86U universal control some rewiring needs to be done. Just get a experienced Pro to do it.:thumbsup:

 

[JScotty]

are you kidding me? I've worked in the field for going on 13 years now, yuri for who knows how man hundreds of years . The conversion kit design specific for his unit is the only one that should have been used but alas, the HO was wanting cheap.

Your belief of one single board being universal to every furnace out there is corrupt and dead wrong. If you think, which apparently you do, that re-wiring a universal board to makeshift the conversion kit is correct than I need your companies phone number, you need to find a different field to work in.

so what's that number?

Whatever you say chief. I've got 9 years experience myself along with my father being in the business for over 40 and we've successfully installed universal boards with no problems. Do we do it all the time? No, but sometimes you can't get a direct replacement & you have to do what it takes to get heat to your customer. Universal boards are not dangerous as long as you read the instructions & install them properly.

 

[Doc Holliday]

Young Skywalker,

I never said universal boards won't work, I've installed hundreds of them, but one is not universal to every unit out there. You need the correct replacement, not supposed to have to re-wire the roll outs and high limits or whatever else. The plug in adapters that come with the new universal replacements take care of that.

No sane and educated insurable heating company would ever have their techs do that.

 

[Doc Holliday]

Whatever you say chief. I've got 9 years experience myself along with my father being in the business for over 40 and we've successfully installed universal boards with no problems. Do we do it all the time? No, but sometimes you can't get a direct replacement & you have to do what it takes to get heat to your customer. Universal boards are not dangerous as long as you read the instructions & install them properly.

I leave a bid for a new furnace and walk away as a last resort, that's how I get them heat. I won't re-nig a board or bypass safety switches, ever. I'm betting you do, right?

 

[TXN TOM]

Whoa! take a moment and think thru this...

Guys,

OK, some great posts, some flames... Let's be nice and put the flames out.


First off, this isn't my first rodeo... I pretty much do my own cars, aircraft, boats, RV's, and you name it, I fix it. Won't even tell you what the family calls me...


But the next time YOU get a WR universal control board, take a look at the instructions, as I did, and you'll see that the Failure Codes LED chart on page 8 has 11 distinct errors or states, each of which indicate the state of the system, or the source of a problem. In order for each state or error to have a unique code assigned to it, each sensor needs to be on its own sensor loop. This is also clearly shown on the wiring diagram on page 4 of the instructions. Using this info, I broke the original harness into the various sensor loops, inserted their wires into the 12 pin connector appropriately, which would be required for the CPU to query each individual sensor loop to determine error.


When I stated earlier that I needed to reverse polarity, and replace the RO sensors, it was because the codes being flashed told me so. In the case of a Rapid Flash, it was 24 V polarity reversed, easy to fix, as the xfmr has 1/4 in connections to the new connector. In the case of the RO sensor, it was actually only one bad sensor; how did I know this? Same way you would, first, the error code was 6 indicating bad RO sensor, and second, I used my VOM to check each sensor in that string, and found one bad RO switch.


In fact, prior to powering up the new board, I buzzed out EVERY sensor, switch, and control on the furnace, to make sure I was not overlooking a bad connection, or another fault that would cause a problem. (We LIVE here, and you think I'm not going to be damned careful?)


So, in reality, I didn't "rewire the board," as someone stated, and I didn't cut any corners. The reality is that the furnace is now probably a safer system than when new, as all of the sensors are set up properly for a state of the art board, which provides additional security with the flame sensor.


As to the original board, it had no flame sensor, but perhaps used the HSI, as speculated in an earlier post; I have no knowledge as to that, but it's certainly possible.


The new board, with the on board diagnostics, will make an easier job of troubleshooting problems with the system going forward.

 

[yuri]

I would still like to see a well lit and closeup pic of where you put the flame sensor. Borrow a digital camera from a friend or work as phone cameras are not too good. I have seen severe delayed ignition, flashbacks and caused a few myself so nat gas will explode like a bomb if not lit properly. Doors have been blown off the front of furnaces and don't even get me going on delayed igniton with oil burners. You may think it is safe but your neighbors have a right to safety also.

 

[Doc Holliday]

this isn't his first rodeo, Yuri. He can build a digital camera with a flame sensor and a control board, mount it to his cesna that he build from egg and flour and fly it into all the dark crevices of the furnace for whatever pics you want. .

op, just messing' with you. we're a laughable bunch here. :thumbup:

 

[yuri]

Beware the infamous "Idiot Valve SVxxxx" I had one get out of sequence and turn on the main valve B4 deciding it was a good idea to energize the igniter. ALWAYS stand to the side of an open burner as you never know what may happen. Lost a few eyebrows and have hairless hands from those lovely events. Jiggling ground wires on a board with a burner on can do the same thng.:whistling2: