The heating air impeller levered off using two screwdrivers.
View of the splines on the motor shaft.
Shaft and bearing. The four motor case tabs which had to be bent outwards later.
The combustion air impeller is easily damaged and using only one screwdriver often breaks the impeller. Our simple low tech solution used two sturdy kitchen knives. Other methods may also be suitable.
These knife blades were 1.5 mm thick and the gap was only 0.3 mm so the knives had to be carefully worked in. After some levering we finally got them passing right through. We could have levered off the impeller using both knives but here we gently knocked in the handles of both knives and the tapering at the handles forced the impeller up the shaft.
The central boss might split if the impeller is not kept reasonably straight during removal.
Three T20 torx screws held the motor.
Motor ready for repair.
The 4 retaining tabs, shown earlier, had it be bent out. They were fairly strong and it took some force. The motor magnets pulled back as the rotor was extracted. The crinkled washer may stick onto the magnets.
Plenty of carbon debris inside the motor created by brushes wearing away.
Magnets and their retaining clips inside the case. No need to take these apart.
Four clips that located into holes in the side of the black cap had to be pressed in before it was positioned resting on the vice jaws. The bearing was knocked free from the cap. On future repairs we would try side to side movement. Otherwise we would use only light taps so as not to move the bearing on the shaft.
Note: The clips have a tendency to move back into position which could cause problems.
First part of disassembly completed. The brushes were quite worn. The bearings seemed ok but we replaced them at the same time to find out how to do it.
Airtronic models have a magnet mounted in the impeller for checking the motor rotation speed.
The black cross moulding removed quite easily.
One of the four clips is slightly protruding at the bottom of the brush moulding. These are shown clearly on later photos of the bearing plate. The cap has one hole showing.
When Carl Dalmas disassembled his D4 the bearing remained in the cap.
The cup shaped washer covers the bearing and is also fitted on the D2.
Drive the bearing from the other side, that also forces the washer free.
Eberspacher Blower Motor Unit repairs
Air heater blowers have impellers (fans) mounted on both ends of the motor shaft. The larger black or orange impeller draws in the air to be heated and pumps it over the heat exchanger. The smaller brown impeller draws in air from the combustion air inlet port and pumps it to the burner. Water heater blowers just have a single combustion air impeller. We would rate motor repairs on modern Eberspacher heaters as medium difficulty, bearings are more difficult than brush replacement. Parts can be easily damaged if care is not taken while disassembling and we advise only taking apart blowers that have failed. Please feedback comments on repairs and repair methods, good or bad, we learn a lot from users problems and experience. If you decide not to repair the blower please donate it to us for experiments and the autopsy pages.
There are 4 main causes of motor failure, listed with the most common first.
1) Carbon brushes wear until they no longer make reliable contact with the commutator. Typical symptoms speed variations, open circuit and intermittent faults, sometimes a smell of ozone due to sparking.
2) Bearing failure. Roughness can often be felt while rotating the shaft by hand and the shaft may have excessive play. Typical symptoms noise, vibration, speed variations, seized motor.
3) Rotor failure. The windings on the shaft are arranged in several segments that are switched by the commutator and brushes. If one segment fails the motor can fail to turn but will do so if the shaft is moved away from that starting position.
4) Commutator damage. Some wear of the commutator is to be expected, very occasionally it could be excessive. Symptoms same as 1 or 3 but far less common.
Airtronic D2 D4 blower motor repair
Eberspacher D2 and D4 blower units. Impellers are fitted on each end of the motor.
Dereks D2 failed several times with fault code 33 Blower speed. Other causes like something touching the impeller were checked. There was no obvious roughness or excessive play when the shaft was rotated by hand so suspicions of a brushes problem. Eberspacher do not sell individual parts, any damage caused during disassembly would mean scrapping the blower. This unit was faulty so we had nothing to lose taking it apart. We marked the impellers and shaft angular position before starting so they can be refitted to keep the best balance. That may not be necessary and it may still not balance after repair but we prefer to do it. We marked the position on the end of the shaft by filing a very small notch on the edge. We also recorded how far the shaft protrudes or is recessed for refitting in the same position.
This is our first repair of an Airtronic motor and minor changes as described will be made when we do another one. Other ways may be as good or better but it worked for us and is a very good starting point. We did try a lot of experiential alternative methods during the repair especially with the brushes.
When Thomas Nilsson dismantled his D4 blower he found the coil assembly on the shaft became loose during the bearings removal process. He gave this advice based on his problem.
Before beginning to take the motor apart measure the distance between the end of the axle and the motor housing. Press the rotor out of the housing, using a press, a vice or a clamp or similar. Do not use a hammer or alike. Once out, measure the distance from the end of the axle to a fix point on the rotor to determine the rotor position on the axle. To remove the bearings, again, press, do not use a hammer. To fit new bearings, press, do not use a hammer. Make sure to put the bearings in the correct position. It is not certain that the positions of the bearings on the axle when the rotor is out of the housing are correct. Double check against the measurements taken before the motor was disassembled.