Saturday, January 30, 2010

How to repair radiator or air condition fan motor

This is a step by step guide on how to repair an electric radiator or air condition (a/c) fan motor for almost any vehicle. The motors are all made basically the same way inside. There will be variations is the shape of the parts depending on the space the motor is designed to fit. There may also be different arrangement of washers and/or bearings so pay attention to what is in your particular motor.
You would want to try this procedure if your car is engine or a/c fan is not spinning when it is supposed to. The easiest way to check if he fans are working is to start the car and put the a/c on. Both fans are supposed to be running now. If you have one fan being driven from the engine via a belt or shaft from the engine then once the engine is running that fan will spin. In this case there will usually be an electric fan running when the a/c comes on. If you have 2 electric fans and the a/c is off, usually one comes on and off when needed to cool the engine or let it heat up and this fan is controlled by a sensor. Having the a/c on forces both fans to run.

If a fan is not spinning when it is supposed to you can connect the contacts from it to a 12 volt supply like directly to the battery to check if there is a wiring fault and not the fan itself. Changing the polarity of the wires to the fan (switching red and black) will cause the fan to spin in the other direction. This is not desired since the blades on the fan are slanted to blow air in only one direction so having them spin the wrong way will cause no air to flow and overheating of the engine. Air is always directed towards the engine block, or from the front of the car toward the back. The motor can be either on the front side of the blade or the back side, and also the blades are slanted for a particular direction.

To get the fan out, there may be a plastic cover along the front edge of the engine bay that has to be removed to access the screws for the bracket which holds the fan in place. Keep all screws, nuts, bolts, washers, press clips etc. in a safe spot where you will not walk over them, kick them away or otherwise lose them. Some brackets are a large frame with the fan motors mounted. To take these out separate the connectors for the electric wires and unbolt the frame. The frame can then be lifted out and worked on.

If you motor cannot be repaired you can get a new motor but you have to make sure it is spinning the correct direction for the way your fan is mounted in your car.

The pic above shows the top half of the motor casing after I split the top and bottom halves open. The bottom half has a couple kinks that hold the halves together. Use a flat head screw driver and pry the kinks away or use pliers and try to bend the kinks away. There is no easy way of opening them. The material the casing is made of is malleable enough to make a new kink if the original is damaged, but try not to damage the casing.

Note: It is very dirty inside the casing as all the carbon powder that comes from the brushes is trapped inside there. Open the casing in a spot that you can afford to mess up and clean easily. A small brush or blower can be used to clean out the dust. The dust is not harmful as it is similar to the carbon used in pencils.

The bottom half is a circular plate with the brushes, springs and appropriate electronics attached. The top half has magnets and the amateur when the casing is just opened. The amateur is held into the top by the force on the magnets on it. The amateur can be taken out by taking the nut off the top end (the end that takes the blade) and pressing that end upside down on the ground and into casing. The amateur should pop out. Make careful note of any washers that are in the casing and around the spine of the amateur. The order they appear is important. Mixing them up can cause either excessive friction which will put more strain on the motor and cause more heat which is bad, or the amateur will not spin at all.

Even before you pop the amateur out you should inspect it to see if it makes sense going further with the repair. You clearly see in my motor there is a groove on the amateur (centre of picture) where the brushes make contact with it. The ring that makes contact is made of many small plates that are close together. It is possible for some plates to be more worn than others. If any of them is worn all the way through then that amateur should not be used any more. The wire connected to the plate can become loose and short circuit the setup, and the extra space from the worn plate can cut away the carbon brushes excessively.

At this point if you amateur is damaged you can get a similar one from another motor or get a new motor entirely. Amateurs that look similar may have slightly varying lengths and diameters of shafts so inspect them carefully.

This picture shows the new carbon brushes in place just after I removed the old ones and soldered the new ones on. The wire on the new brushes can be trimmed down to an appropriate length is necessary. They should not be too long because they must not touch other metal parts to short circuit. When the brushes go into the slot the wires curl up and the coil can also short out so watch how the wires bend when you load the slots. Try to get them to bend horizontally and not curl. The springs can be loaded into the slot using either end first.

Also note here, you can see one of the kinks in the top right corner of the picture that is used to hold the top and bottom halves of the casing together.

This is another shot of the same thing but with the brushes more organised.


1 comment:

  1. Good job. I'll probably try to make a video the next time I'm doing it.