One day when I arrived at work I noticed an unfamiliar smell coming under the hood. I thought the smell was originated from some insulation material that was overheated, so I looked through all battery terminal connections which seemed ok and did not smell at all. The smell wanished pretty fast after the car was stopped so it was not easy to find its source.
After one short drive when I once again tried to find the source of the smell I noticed that one of the motor terminals was very hot while the other one was cool. The terminal connections looked tight and identical so I realized that I'll have to search for the problem inside the ME1003 motor.
First thing to do was to remove the brush holder cover:
Quite a lot of sand can be seen on the brush holder. At this point no faults could yet be seen.
Next the brush holder was removed for closer examination. It was far easier than I thought, this motor is clearly made for easy maintainance.
Once I got the brush holder on a table the problem could be seen:
The terminal on the left had blackened due to a bad contact caused by a loose bolt. By smelling it from a close distance it could be confirmed that this is the source of the smell. The terminal on the right looks healthy and its bolt connections were tight.
I also noticed that the brush springs were all not identical. One of them was significantly weaker than the majority:
In the picture above two spring on the left represent healthy springs in my opinion. The one on far right had loosed its form possibly due to overhating due to the loose contact as that spring was located on the brush closest to the overheated terminal. I tried to give back its original form but not with a very good result. As my brushes are still quite new the sping force on their current position is quite good also with the damaged brush spring. But as the brushes get smaller the damaged spring will not be able to deliver the designed amount of force, so I'll have to keep an eye on this.
To get back on the road I replaced the overheated bolt and nut and cleaned the contact surfaces:
The picture above shows the result of the repaired contact. I also checked the tightness of all other current carrying bolts and I would consider that 40% of them were too loose! After tightening all of them I reassembled the motor and I've been driving again with no mysterious smells;)
Knowing that I have a weak brush spring and that the current carrying bolt connections can get loose again I searched the internet for others experiences. I was more that happy to find this link:
http://evmc2.wordpress.com/2012/11/17/motenergy-brush-holder-me0804-rev-a-dept-of-a-closer-look/
I am seriously concidering of ordering that improved brush holder version with those welded connections and larger buss bars. It seems like an excellent solution for my brush holder situation!
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