Help me fix a space heater

[Squisher]

So the wife says she smells something and I thought it was just my underwear, but when I picked up the space heater I keep behind the couch and see it smoking I figured my underwear were safe for another day. Before you guys get all out-of-sorts by keeping this behind the couch, the heating element is encased in water is OK for this small of a space.

When I opened it up I saw some arcing in among the metal fins on the back of the thermostat here :

But, the real heat is coming from this box, which I have to think is a relay. Two wires coming out of the box go up to indicator light to show the heater is actually heating.

Closeup of overheating box:

This space heater wasn't cheap given it's like 6 feet long and water filled. I'd like to fix it. If needed I could maybe do some sort of rudimentary schematic.

 

[Rubycon]

That "overheating box" is a full wave bridge rectifier probably in the 20-25A range. Was it mounted to anything? They usually have a hole in the middle and are mounted with a 1/4x20 stud to a larger metal plate for heat sinking. Without this heatsinking there is some derating as they will run hotter. It may be OK just feels hot to your hands. They can usually run up to 80-85C with no issues. Junction SOAtC may be well over 100C!

The arcing is the contacts. Those are probably directly connected to the element.

Do you have a model/make of this heater?

 

[Red Squirrel]

Let it cool off then see if you can bypass the thermostat, see if it arcs/smokes again. This will rule out the thermostat as being the problem (do lot leave it unattended during this test!) If it seems ok after a typical cycle time (15 minutes maybe?) then I'd look at replacing the thermostat. Not sure where you could get one that fits, but if it's a simple 120/240v 2 wire thermostat those should be easy to find and you could wire it. Make sure all the connections are tight too, maybe something just got loose which would cause a path of high resistance.

 

[Squisher]

There is a hole in the middle, but the box wasn't mounted to anything. It just rattled around in the area you see blackened. Make is Fahrenheat. I'll look for the model #.

 

[Rubycon]

Wow that is crazy not to have it bolted down!

Fahrenheat! Funny! Centipheat would've worked better.

 

[Squisher]

Model# LFP6152

 

[Rubycon]

Might want to check this out!

http://www.fixya.com/support/t1399749-fahrenheat_lfp

 

[Squisher]

Might want to check this out!

http://www.fixya.com/support/t1399749-fahrenheat_lfp

Thanks. Maybe, with all heat sinks I have laying around I can shoehorn one in there too when I get the new part.

 

[Rubycon]

You may want to check that rectifier with a DMM. It may still be good!
Good thing you caught it before it got worse. Not all the time will these things just hard fault the line. (which would trip the CB on that branch circuit) Something behind the couch that starts to glow is not good!

 

[Paperdoc]

You could have dirty / poor connections in two areas. With the whole thing unplugged from the wall, remove each connector in turn (one at a time) on that bridge module and examine the connectors. If any are badly discolored or blackened, either clean the metal surfaces down to bare metal again, or replace the ones on the end of the wires with new ones (they crimp on). As you re-connect, make sure the connector makes a tight grab on the blade it slips onto.

At the thermostat, that multiple fin thing is actually a stack of metal plates that are the springs, and each carries a metal button that is the contact point in a switch pair. Look closely at those metal buttons' facing surfaces. If they are blackened, try to slip a sheet of fine emery cloth between the contact points and run it through to clean off the contact's surface. Reverse the emery cloth to get the other button's surface cleaned. A little bit of arcing is normal at switch contacts, but if they get too blackened they will arc and spark a lot, hastening their own deterioration.