USSC 4840 problem(s).

[Mr. Whippy]

My 4840 is 2 years old. The first two seasons, it ran flawlessly. This fall, when I plugged it in, it did nothing. No lights, no fans, no sounds. Using a multimeter, I found 120V where power plugs into the main board. There were 2 blown fuses, which I replaced with no change.

I called USSC. They suggested the secondary board (in the small door), so I purchased one and replaced it. No change. Then I replaced the communication cable (from main board to secondary board). No change.

So, I purchased a new main board (attaches inside the body of the unit). Now, I got fan noises and ALL the lights on the front panel flash. I could get pellets to drop into the pot and it would burn. At that point, I thought the front panel led pad was wonky and was willing to run it that way.

Now, it makes a trill noise in a repeating pattern, doesn't drop pellets and doesn't light. The panel lights still all flash.

I am assuming a vaccuum problem, but I don't know. It still doesn't explain the flashing lights. When I called technical support at USSC, they had no additional suggestions for me.

This is getting a bit frustrating...

Any help is appreciated.

 

[zinger827]

Hi did you plug wiring back to where it belongs? Here is a pic of wiring to board. Maybe the RTD connectors are backwards?

 

[Mr. Whippy]

Hi did you plug wiring back to where it belongs? Here is a pic of wiring to board. Maybe the RTD connectors are backwards?

I photographed and labeled before switching them on boards so I think they're ok. Its running a bit as you can see in the picture but it doesn't continue to feed and the toch panel is unresponsive.
All 5 heat range lights flash in unison, the on and off lights flash alternately and the E light flashes. The lights for door and press don't light, even if I open the door.

I can upload a video if that helps

 

[Mr. Whippy]

Oh, and it only feeds for one cycle

 

[zinger827]

Best person to talk to about it at Us Stove is a Ashton. She is smart when comes to the 4840. All lights lighting up sounds like Control Board? Do you have a dvm ohm meter? You can test the RTD's see if you have a bad one. Just unplug it from Control Board after Unplugged of course and see if you get a 1000 ohm reading that's what they both should read. I'm no tech but I had a 4840 I repaired and learned a little about them. That's about all i can suggest.

 

[Mr. Whippy]

Best person to talk to about it at Us Stove is a Ashton. She is smart when comes to the 4840. All lights lighting up sounds like Control Board? Do you have a dvm ohm meter? You can test the RTD's see if you have a bad one. Just unplug it from Control Board after Unplugged of course and see if you get a 1000 ohm reading that's what they both should read. I'm no tech but I had a 4840 I repaired and learned a little about them. That's about all i can suggest.

That's good info. I'll test them. Yes, I've replaced the main control board (which got me power back) and the secondary board in the door AND the com cable between them

 

[Lake Girl]

Second post has the pdf technical manual for the 4840 https://www.hearth.com/talk/threads/ussc-troubleshooting.158667/

Hope that helps...

 

[Mr. Whippy]

Thanks! I downloaded it. My big question is, if all 5 heat setting lights flash, is that the same as the "flashing 5" ? I thought that might mean just the 5th light alone.

 

[Lake Girl]

Multiple flash codes are possible per the manual. Looks like both RTDs, exhaust and room. Wondering if you got them hooked up wrong on the board?

 

[Mr. Whippy]

Multiple flash codes are possible per the manual. Looks like both RTDs, exhaust and room. Wondering if you got them hooked up wrong on the board?

I guess that's possible, but I labeled wires, so I know they are attached to the correct pins on the board. Something catastrophic happened on that main control board because 2 fuses were blown and when I swapped the boards, you could see where the right hand side of the board was discolored, like an overvoltage.

Can I just switch the the terminals on the pins and retest or will something go kablooey? (That is, two wires connect to the labeled pins, I'm thinking of swapping which they're connected to, one at a time, to see if I have them on the "wrong pins"-- although on simple switches, that usually doesn't make a difference...)

 

[Mr. Whippy]

Alright. Both RTD's test at exactly 1000 ohms.

Assuming they're not the problem?

 

[Mr. Whippy]

Video of what I have

 

[Mr. Whippy]

Also, once up to temp, the fan does blow hot air

 

[Mr. Whippy]

Update:

The 4840 has a new controller board, new com cable, new secondary board NEW TOUCH PAD (done today), with no change. Same flashing lights. It will initiate and ignite when the power is turned on, the room fan runs but it will not continue to drop pellets. Messing around with pushing touch pad buttons, one time (only one time) I was able to get it to continue running for several hours, but I cannot repeat that today. I have cleaned out the unit.

I have no idea what to do next.

 

[FirepotPete]

Update:

The 4840 has a new controller board, new com cable, new secondary board NEW TOUCH PAD (done today), with no change. Same flashing lights. It will initiate and ignite when the power is turned on, the room fan runs but it will not continue to drop pellets. Messing around with pushing touch pad buttons, one time (only one time) I was able to get it to continue running for several hours, but I cannot repeat that today. I have cleaned out the unit.

I have no idea what to do next.

I've seen RTD's in industrial settings that tested good before installation and then didn't work properly. About the only thing you can do at that point is to swap them out. Bench test the new ones before install, make sure you don't shorten the wires on each one so that one side is longer than the other, they should be the same exact length for each probe.

Before doing that though, check where the RTD's are mounted. Assure that they didn't get bent or warped from heat and are touching anything. If they are mounted in a well then when removing them and reinserting they should move easily without feeling them touch anything when extracting or reinserting them. Also if well mounted try and look inside the well to make sure nothing has fallen in there and could touch them.

 

[Mr. Whippy]

I've seen RTD's in industrial settings that tested good before installation and then didn't work properly. About the only thing you can do at that point is to swap them out. Bench test the new ones before install, make sure you don't shorten the wires on each one so that one side is longer than the other, they should be the same exact length for each probe.

Before doing that though, check where the RTD's are mounted. Assure that they didn't get bent or warped from heat and are touching anything. If they are mounted in a well then when removing them and reinserting they should move easily without feeling them touch anything when extracting or reinserting them. Also if well mounted try and look inside the well to make sure nothing has fallen in there and could touch them.

Whelp. With that (and the flashing indicator lights) I guess I'll replace the Room RTD and see if that helps. There is some red sealant on the probe end so maybe that's part of the problem (although I doubt the unit ever "overheated").

As a side note, I left the unit "on" (ie the power on to the unit) and it actually ran correctly yesterday afternoon, despite the flashing control panel.

 

[Mr. Whippy]

Whelp. With that (and the flashing indicator lights) I guess I'll replace the Room RTD and see if that helps. There is some red sealant on the probe end so maybe that's part of the problem (although I doubt the unit ever "overheated").

As a side note, I left the unit "on" (ie the power on to the unit) and it actually ran correctly yesterday afternoon, despite the flashing control panel.

Replacing the RTDs with a new RTD (both the Room and Exhaust RTDs) did not change the light flashing pattern. The stove does seem to work, although start up is a little strange, it will eventually run. Also, the off button does initiate shutdown correctly.

 

[Mr. Whippy]

So here's the solution:

US Stove didn't have a solution so they offered a new stove. The 4840 is not in production so they offered me any of their other stoves so I decided on a Big E (SP 1000), mostly because it can be controlled by a thermostat. I really liked the form of the 4840, but this unit will do the job.

 

[zinger827]

Nice you got a replacement Stove for your 2 year old stove. That will stove will kick out the heat. They already stopped production on the 4840 no kidding.

 

[Lake Girl]

After spending that much on the replacement parts, it's nice that they offered a new stove.