Oil Furnace Repair: Furnace Humidifier Troubleshooting

Conducting an oil furnace repair can seem like a daunting prospect for an amateur, but before you call in the professionals, there are some basic assessments that you can make of your furnace humidifier in order to ensure that you are not getting a large repair bill for something which you could have managed yourself. Although most of an oil furnace repair should only be done by an expert, you can try to do some simple troubleshooting which will help you to work out what the problem is.

Understanding the Humidifier

An oil furnace humidifier comes in two different styles. In order to do any troubleshooting, you will have to work out what kind of humidifier you possess.

A reservoir humidifier uses a tray of standing water and a turning drum-shape which together produce the moisture required by the system.

The flow-through humidifier is the most common. In this, water flows through the humidifier and drains away. Flow through humidifiers are better, as you have fewer chances of bacteria developing in the humidifier's standing water, causing illness. Flow through humidifiers are mounted on the air duct, and are connected to hot air supplied by the furnace.


Before you begin troubleshooting, turn your furnace off at the disconnect switch. This will ensure that while you are testing the machine, there is no chance of electric shock. Check the fuse box of the surrounding components, and the humidifier itself. Take out the fuse, and either use a multimeter on it, or place into some system that is working. If the fuse is broken, replace it, and test the humidifier again before continuing.

More Troubleshooting

Next, check the water in the humidifier. They need water to run, and if it has evaporated, or the water supply has been lost, then the humidifier will not work. Check the copper water line to ensure that water is not leaking out. If there appears to be little water in the system, or there is water damage on the floor, you can attempt to repair the water yourself, or call in a plumber.

If there is plenty of water available in the pipe, check the inlet orifice. If these parts have not been used for a while, then you may find that they have seized or clogged. This can prevent proper working of the humidifier, so check these to make sure that they are all working well. If parts of the inlet tube or orifice are not working, then you should consider replacing with a similar part, available from a hardware store.

Further Troubleshooting

Another place to look is the evaporator pad. These serve to collect any minerals in the water, and often need changing once a year. If you have not changed your pad yet, then you can do this while you are checking the humidifier. Make sure that it has not become tangled in the outflow pipes, or is otherwise preventing the movement of water in the humidifier.

Check the Humidistat by unscrewing it from the mount, and looking for loose wires, or blown circuits. If you still cannot find a problem in your humidifier, then it is a good idea to call in a professional.