Cooker Hood Motors
The motor in a cooker or extractor hood is a very simple one, almost without exception it is a small brushless induction coil motor that requires no maintenance at all.
One common reason for a fan motor to fail is a failure to maintain the cooker hood correctly, i.e. not cleaning or changing grease filters regularly. The grease, steam and so on in a vapour gets into the motor and cause it to drag or slow meaning it’s working a lot harder then it should have to and, it ultimately fails.
Proper maintenance of the filters is absolutely essential in maximising the life of your hood.
Before attempting any work on your cooker hood ensure that you remove all power from it, it is not required to test or to diagnose any problems and, as it carries mains current, there is a high risk of electrocution should you fail to do so.
Ordering a New Motor
It is very important as with many spare parts these days, that the correct motor is ordered for your specific cooker hood model.
Coker hood motors come in all shapes, sizes, ratings and fittment and while many look the same or similar they are all too often not interchangeable.
Should the incorrect one be ordered then it may not physically fit, can be wired differently internally and so on. Fitting the incorrect motor, if the electrics are different, can also blow the switches so, you need to make sure you get the correct motor.
In order to do that you need the model number at the very least but, increasingly, the production code, serial number or suchlike as well. You will find this on a small rating plate sticker inside the cooker hood, remove the grease filters and (somewhere) up inside the hood you will find this.
Without that, it’s often little more than guesswork at a replacement motor.
Cooker Hood Motor Not Turning
If your cooker hood motor will not turn by hand or, seems stiff and hard to turn then it is possible that the bearings have failed in the motor if it has been in operation for a long time, this isn’t all that common but it can happen. Usually as a result of moisture or grease ingress to the bearings.
The other main cause of this is simply ingress of grease through poor maintenance, the grease builds up in the motor and eventually causes it to seize up or run slowly. This can burn out the motor as well in some instances.
If the coils are still okay, cleaning the motor out may bring it back to life but, as often as not, the only cure is to replace the motor entirely as if it’s got to that point then the chances are that it will be irreparable damage that has been caused.
Often when the motor is prevented from turning in this way you will hear a humming noise from the hood, that’s the motor trying to run but not being able to do so.
Whereas, if the motor isn’t getting up to the speed it should then you may well find that your cooker hood either doesn’t extract correctly or hardly at all.
Multi-Coil Cooker Hood Motors
The motors you will find normally come with several wires on it, each performs a function of the motor’s speed depending on the selection made by the switch assembly.
The most common way to deal with the multiple speeds is to use two separate induction coils in the motor set to turn the armature, connected to the fan, at two different speeds, a low and a higher speed. This immediately gives you two motor speeds and, with both in operation, the third speed.
This is why, on cooker hoods with this type of simple arrangement, that you will often see wires linking the coils, so that they can be used in tandem or, as one to give the different speeds.
Also why you will usually have at least four wires to the motor, a negative and live feed along with two live switched for each coil, these are switch in the control switches of the control board to operate the coils as required.
Electrical Fault Diagnosis & Testing
Ordinarily when these motors fail what you get is one of the two coils faulty so, you will only get the high speed or the low speed and not the highest extraction speed where both coils are in play.
It is very unusual to get both coils faulty at one time.
If you have just one speed faulty but both others work, chances are that it’s the cooked hood switch that’s faulty and not the motor.
The coils are easy enough to test, a simple continuity check of each should give you a reading across them if they are okay, if you get no circuit then the coil is faulty.
If both coils read okay it’s possible that the armature in the motor is faulty but if that’s the case then you will get nothing from the motor at all.
Variable Speed Motors
Of course on more upmarket cooker hoods you can find ones that will have multiple speeds or even infinite speeds controlled by an electronic control module that offers a control along the lines of a dimmer switch, you can simple vary the speed as you see fit.
These tend to be far more complex in the way that they are set up, often with an input module that you interact with on the front (or a remote control of some sort) connected to a another power control module that will control the speed level of the motor.
These types of cooker hood are a lot harder to diagnose and will often require specific knowledge to work out where the problem is as, the motor is single speed and is being fed variable levels of power from the power control module, which is in turn, being controlled by another electronic component.
They are not exactly rocket science but, it’s easy to get confused with them as you need to be able to test the motor coil again to make sure that’s okay then understand if the input control is sending the signal to the power control module to then engage the motor.
If the motor is faulty you will often get nothing, the hood appears to light up and the functions can all be selected but it doesn’t do anything but, the same will often be seen if the power control module is faulty as well. And, if the input is faulty, same again as it’s not telling the power board to fire up and go. Then there’s the wiring harness between them all.
In short, for each of these types of cooker hood you either need information about the specific hood or, you need to have time to sit and work out what area the problem lies in and, this can be more challenging than a simple cooker hood to figure out.