Repairing a Heat Selection Knob on a Fan Heater

Well this was frustrating! The range selection knob on my fan heater was turning without doing anything. I decided to try and open the case to see what was wrong, but of course the manufacturer had used security fixings, relatively uncommon triangular ones too!

I have lots of shapes and sizes of Torx bits and screwdrivers, but they would be useless in this situation. Luckily I managed to undo two of four screws from the upper side of the heater using a large jeweler's screwdriver. This allowed me to pull the case apart just enough to remove the knob.

Part of the shaft of the knob had snapped off in the switch. Gluing, even with superglue wouldn't be a permanent fix because the resistance of the switch was such that a large torque was needed to change range.
First I removed the broken-off piece of shaft from the switch using a woodscrew. The piece was hollow as was the other piece of shaft remaining on the knob. I decided to attach the two pieces together using a rivet pin.

I hoard lots of scrap, and rivet pins are part of my collection, along with self tapping screws, springs, nuts, washers and all sorts of other miscellaneous items! Some of these pins were exactly the right diameter.

I dripped some super glue into the hollow interior of both sections and also on the broken surface, then joined the two pieces together. Some heat from another fan heater accelerated curing of the glue.

After trimming the pin, I replaced the switch, cost of repair? Zero!

What Does the Voltage Rating of a Fuse Mean?

Image Courtesy, mtself CC BY SA 3.0 via Wikimedia Commons

The current rating of a fuse specifies the current which the fuse will carry without blowing. Once the current exceeds this value, the fuse will eventually blow. The characteristic of a fuse is such that if the current in a circuit is moderately higher than the fuse rating due to an overload, the fuse will take some time to blow, possibly seconds, minutes or tens of minutes, depending on the magnitude of the overload. If the current is a lot higher e.g. in the case of a short circuit, the fuse will blow in a few tens of milliseconds. While a low voltage or high voltage fuse will blow when the current exceeds the current rating, the current flow in a mains powered circuit can be extremely high (possibly thousands of amps) in a short circuit scenario because the current is coming from a large transformer outside the home. The breaking capacity of a fuse is specified in joules or kiloamps and a mains fuse could have a rating of 10000 amps or more. This is the maximum current the fuse can carry without rupturing. Usually fuses for mains equipment or distribution circuits have a ceramic body to withstand the heat and shock when the fuse blows. The fuse is also filled with quartz sand to absorb the heat and shock and quench the arc when the fuse blows. A glass fuse could simply rupture and possibly cause a fire if it carried such a heavy current. Glass/low voltage fuses may be used on the secondary side of the transformer in the power supply of equipment because the current output of the transformer in a short circuit situation is limited.

Why Won't my Lawn Mower Start?

Lawn Mower Won't Start?

As the days lengthen, and temperatures rise, the grass cutting season isn't far away. So you drag your mower out of storage over winter, fill the tank and pull the cord..., and pull it again....and again....and of course nothing happens - Well that's typical!

If you leave fuel in the tank over winter, the carburetor can get gummed up with varnish deposits, jets get clogged and small delicate parts can seize. Ideally you should run the engine dry before overwintering and/or use a fuel stabilisation product such as Stabil.

Engines need fuel and a spark to run, plus good compression (the engine needs to hold pressure when mixture is compressed)

Checking the Spark Plug

First check the lead is pushed onto the plug properly and this wasn't the cause of non-starting. Move the mower to the shade so that it's easier to see a spark, remove the spark plug and re-attach the lead. Leave the threaded part of the plug in contact with the engine block and  pull the starter cord. The chances are that you won't be able to see the plug from your vantage point behind the mower, so an assistant may be able to aid you by pressing the plug against the block (using a plastic bottle or whatever to avoid shock if the plug lead is damp). The spark should be bright and blue.

When replacing a plug, make sure there's nothing on the threads such as dirt or grit, and make sure it isn't cross threaded by screwing in by hand before tightening with a plug wrench. If the plug is cross threaded, it will be difficult to turn by hand.

Fuel  Starvation

This means the engine isn't getting fuel. On engines with the tank above the carburetor, fuel first flows to a device called a float bowl. This is like a toilet cistern and prevents fuel just running into the carburetor. The bowl fills and once its full, a float (which functions just like the ballcock in a toilet cistern) cuts off flow. Sometimes the intake to the bowl can get clogged or the filter in the fuel line can be blocked, either of which can cause fuel starvation. When you remove the bowl, petrol should flow freely and stop flowing when you push up the float (use a jar or tin to catch fuel).

Another cause of fuel starvation is a clogged main jet. You can get carburetor cleaning aerosols which have a straw just like on a can of WD40. You insert the straw into the jet and press the button on the aerosol, the spray flushes the jet. If you have an air compressor, you could try using the a blow gun attachment to blast air through the jet. Avoid poking nails, wires or other objects through it, which could damage the jet which is made from brass.

Compression

Check the plug is screwed in tightly. Don't over tighten as you can damage the threads.

Read my full version of this blog post on DenGarden.com. It has lots more info on lawn mower troubleshooting with loads of pictures and goes into much more detail:

 

https://dengarden.com/landscaping/Why-Wont-That-Lawnmower-Start

Check Your Electrical Outlets and Prevent Fire

I have just being listening to the radio on which a story was recounted about a person whose house was burnt down by a fire started by loose connections in an electric socket outlet. This just shows how electricity can be our enemy if we don't look out for warning signs, and maintain the wiring in our homes.
So what can you do to prevent fires?
Don't overload sockets.
Ensure you wiring is up to standard and circuit breakers or fuses are properly rated for each circuit. Don't replace a fuse with a higher rated type.
If a plug becomes hot, this is a symptom of a loose electrical connection. It is normal for power cords which supply a high powered appliance such as a heater or tumble drier to become warm, and plugs which have an integrated fuse (standard in the UK and other countries) can become warm also. It is not normal for a plug or socket outlet to get hot. This is either caused by the screws which hold the wires in the terminals of the socket or plug becoming loose, or alternatively the brass strips in the socket which grip the pins of the plug may not be doing so adequately. Either scenario will result in arcing and potentially this can start a fire if sparks are produced, or the insulation on power cables catches fire. Sometimes arcing can produce clicking noises, or a burning smell can be detected, but not always. Don't leave high powered devices switched on when no one is at home or you are in bed.

For further information on this and a comprehensive guide to avoiding fires in the home, check out my article on HubPages: http://eugbug.hubpages.com/hub/Common-Sense-Fire-Safety-in-the-Home

Image courtesy PACAF http://www.15wing.af.mil/news/story.asp?id=123143636