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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8703
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Using the Robertshaw ds 845, and someone else had the same

Customer Question

Customer: Using the Robertshaw ds 845, and someone else had the same problem. Igniter goes on and stays on, and the system shuts down. Red light is flashing on the module. The system has worked pretty well for the last 17 years, but has never been serviced. The wires and connections are connected, but again it has never been serviced.
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Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, so far it sounds like a bad printed circuit card (90% chance of that) or a bad gas valve or bad plug in connector.

Next please attach a well focused, close up photo of the wiring diagram glued inside the service panel, the picture needs to be taken from straight on, in very good light.

You can use the paper clip- icon at the right end of the tool bar at the top of this dialog box to attach it here.,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If you have an error code showing, tell me what the code read out is on the wiring diagram or a sticker next to the diagram please.

If there is no paper clip-icon, look for the '+attachfiles'link at left of your send button.

I can mark it up with trouble shooting instructions.

We can go from there. I will be up tonight for another hour or so, then back early in the morning, if I miss you tonight I will pick up your response first thing in the morning,

Customer: replied 1 year ago.
Hi Phil,
Thank you for your response. I don't see anything that looks like a circuit diagram on my end, but I have provided the most technical information about the unit I could find. I am hoping that it can provide a little more insight for you.
Expert:  Phil replied 1 year ago.

Its most likely a bad ignition module, especially if you do not see or hear any sparking.

If the igniter is sparking, I need a photo of the 10 x 12" wiring diagram sheet of paper glued to the inside of the blower service door, you have to remove the door to see the diagram to coach you on a further diagnosis.

Photo needs to be taken from straight on, up close and very well focused,

I am off to be shortly but will be back at 6 am to pick up your response, we can go from there without a time limit.

Customer: replied 1 year ago.
Let's pick it up in the AM. Appreciate your assistance so far.Will definitely need coaching on where to find this diagram. As an FYI. I am getting sparking. It just keeps sparking, then the unit shuts down and I get the blinking red light on the Robertshaw module. As for a blower, I am pretty sure I don't have that.
Expert:  Phil replied 1 year ago.

Hello again, if you have a floor furnace or wall furnace you may not have a blower.

If you have central heating, then there is a blower.

If you can attach a photo of the furnace with the service panels off, taken from about 10 feet away so I can see the whole thing, that will help a lot.

Customer: replied 1 year ago.
This is a stand alone fireplace. Guess we should have covered that off from the beginning. Picture attached.
Expert:  Phil replied 1 year ago.

Thanks, ***** ***** case there are only two components, that ignition module you send data on, and the gas valve... the chances that ignition module is bad, or its attached igniter is bad are in the 90% range, the chances that the gas valve is bad and not opening when it gets power, is in the 10% range.

If you have a good multi meter and if you can find the wiring diagram for the heater, I can coach you on that diagnosis... or you can just replace the ignition module and see how it goes.

Might have it, let me know what you want to do, we can go from there without a time limit.

Customer: replied 1 year ago.
I have a good multi meter. But you would have to walk me through how to use it. I would rather try to test to rule out other problems before placing the order.What do you consider the heater? Is that the part that generates the flame?
Customer: replied 1 year ago.
Looking at chat groups that are out there, some people have replaced the module without any luck, so want to see if we can zero in on whether that is the problem. Too much delay in getting a module only to find out that wasn't the problem. Want to cover off that 10% first.
Expert:  Phil replied 1 year ago.

OK, I need a wiring diagram of that unit to coach you on the diagnosis.

Lacking that I can try it with pictures... I will be very specific...I need a picture of the TOP of the gas valve, that shows any wire connections, and a side shot that that shows the tube connections.

And a photo of the pilot light assembly.

Expert:  Phil replied 1 year ago.

The more I can see, the more efficient I can be in helping you diagnose this.

I also need to see a photo that shows all of the wire connections to the ignition module and the entire top so I can read the markings.

Expert:  Phil replied 1 year ago.

The more I can see, the more efficient I can be in helping you diagnose this.

I also need to see a photo that shows all of the wire connections to the ignition module and the entire top so I can read the markings.

Customer: replied 1 year ago.
It is 10AM my time now, and getting on with my day, unfortunately, away from the house. Will circle back later.
Expert:  Phil replied 1 year ago.

That will work, hopefully the www problems will clear up by then, right now its a mess.

Customer: replied 1 year ago.
Hi Phil. Didn't have a chance to get to this today. I am full on tomorrow, and will sit down and spend time on this Sunday. You available then??
Expert:  Phil replied 1 year ago.

I will be here, hopefully the www problems will be sorted out by then

Customer: replied 1 year ago.
Just to be clear. The www problems you are referring to...are those Internet problems on your end? Not sure what you are referring to.
Expert:  Phil replied 1 year ago.

regarding the www, I am referring to the internet broadly... it seems to be a problem in many areas around the US today, I have no idea at all beyond that... it slowed up a lot in my entire region... I get some web sites OK, but not others around the world. I am getting 2 bars where I normally get 4 bar signal strength. It could be just my ISP, but whatever it is, is also producing erratic behavior from other servers in other states that I do business with.

Customer: replied 1 year ago.
Hi Phil,
Okay, ready to get to it. Going to take the time I need today to sort this out today. I am thinking that I probably just need a new ignition control module, since this is clearly a ignition/spark problem. So if we can work together to isolate that problem to determine if that is what I am dealing with, that would be appreciated.
Expert:  Phil replied 1 year ago.

No problem, I do have to come and go however to do research and type answers.

If you can get me a picture of the igniter module so that I can see the screw heads where the wires area attached, in very good light, that will work.

Customer: replied 1 year ago.
Here is a pic of the ignition module. If you can assist me in determining if this is the problem, that would be great. I have also looked around on the internet, and they are very expensive for me, since I live in Canada. So, before I take the plunge and buy another one, I want to make sure that is the problem. As for the picture, I realize that I didn't get a great shot of the wires, so if you need anything else, I can give it a shot. The unit wasn't screwed down, but it seems grounded, and was operating for over 25 years. Maybe it has just thrown in the towel.
Expert:  Phil replied 1 year ago.

I need a much better shot of the wires attached to the module, good enough that I can read the terminal markings, and know which wire goes to which terminal.

Expert:  Phil replied 1 year ago.

You will need a bright drop light, or table lamp to a shot like that.

Customer: replied 1 year ago.
Hope this helps. I am heading out for about an hour, and can pick it up again as you need more info.
Expert:  Phil replied 1 year ago.

Hello again, follow the various wires until you find the 24volt control transformer, make sure that is putting out 24volts, if it is keep following the wires from the module and from the gas valve until one of those runs into a small round black plastic high temperature limit switch, that is about all that can be bad except the module or the gas valve.

A module that old has already exceeded its normal life span by a factor of 3 or 4 to one, so if you intend to say in the house replacing the module would not be a bad place to start

You can also jumper 24 volts directly from the transformer to the gas valve and you should hear it open, if it opens we know that it is either the ignition module or the high limit switch is bad. Do not leave the jumper in place longer than the 2 seconds or so that it takes to do the test.

Let me know. we can go from there.

Customer: replied 1 year ago.
Okay. Here is what I have done so far today.
1. Made sure that the transformer was putting out 24 volts. Confirmed.
2. Attempted to jump from the transformer to the gas valve. I have attached a picture of my attempt. Did not hear anything happen at all. Only tried it for a little over 1 second, since I didn't want to take a chance of damaging the unit.Wasn't able to identify anything that looked like a high temperature limit switch. The only components seem to be the transformer, the module and the gas valve. But I am the amateur here....I guess at this point, it looks like we are zeroing on either the module or something associated with the gas valve?
Expert:  Phil replied 1 year ago.

Thanks, ***** ***** picture does not show me the gas valve wire connections on the actual gas valve so I am unable to tell if you jumpered the 24 volts from the transformer (both wires) to both terminals on the gas valve.

There is also a high temperature safety cut out switch in series with the gas valve... I mentioned earlier... you have to follow each of the wires from the gas valve until you run into it, and fit a jumper wire across it, it the fire place now fires, you found the problem, if not, the problem is either the gas valve or the ignition module.

You can also remove both wires from the gas valve and check for an ohm read between them, it there is infinite resistance, same read you get when holding both probes in the air, then the gas valve is bad... if you get an ohm read at all, the gas valve is probably good.

If you appreciate my input so far, locate the "rate your expert" link, and rate my work positively... we can go from there.

Lacking that I can spend days with a customer at my own expense,without any compensation. Rating does not increase your charges or close the question and it allows you unlimited follow up.