As I continue on with this guide to finding the problem with your E-bike, let me say that it is important that you read Part #1 that I published last week. The notes about safety, knowing if you should do this on your own, and the sequence of tests are all part of this post.
So, you have tested or replaced your battery and the lights on your panel are still not on. The next step is to check that you are getting that power to the ECU (electronic control unit). It is normally located in the frame or rack and is not that hard to gain access to. Note how it and the wires are tucked in to the compartment before and as you pull it out of its hiding place. Use the voltmeter to confirm the correct voltage is being delivered to it.
There is a possibility of a broken wire or a bad connection between the battery and ECU. Look for signs of overheated wires at the connectors, that is a sure sign of trouble. There is also a chance that the handlebar mounted display is faulty, but I rarely find this to be the case.
At this point you can use the meter to check the brake safety cut-out switches for correct operation. Also, you can check the throttle control for the correct signal it should send to the ECU. These tests won’t help if the display lights aren’t on, but if they are, here is where you can do it. A wiring diagram can be quite helpful at this stage of the testing. Make sure to power off the bike and disconnect the wires at the ECU during these tests.
The brake switches will be a simple continuity test, while the throttle test is different. Most (but not all) throttles are basically a dual 5K variable potentiometer that works a lot like an old fashioned volume control on a radio. The ohm reading should read (and change) in the 0- 5K range when the throttle is twisted or pushed. If you do decide to change the throttle unit, make sure to get an exact replacement from your bike’s manufacture. If none of these tests show a bad component, then you can assume the ECU is bad. Once again, an exact replacement unit is the best.
Let’s say the lights on your control panel are working, but you still can’t get the motor to run (and you have tested the brake switches and throttle unit).. Chances are you have a bad ECU or motor. There are a few other things that it could be, but on most bikes you will find one of these two items are the culprit. On a true pedelec bike (no throttle), or an intelligent pedelec bike (with a load sensor hooked to the pedals or rear drop-out), the testing could be beyond the scope of this article.
On those bikes, I strongly suggest you have a factory trained tech do your troubleshooting and repair. At minimum, talk to one on the phone to guide you. True pedelecs use a hall sensor on the bottom bracket to trigger the motor. These are not too complicated. An intelligent pedelec uses a computer and sensitive load sensor that can be quite complicated. The load sensor can go out of adjustment and I have dealt with this, but once again, complicated.
Here are a few tips on deciding if your motor or ECU is the bad guy. If you can hear the motor run, but it won’t turn the wheel, then the internal reduction gears are stripped or broken. This you can fix. If the motor jerks, but won’t run, then it is the ECU. If the motor won’t run at all, then it could be either the motor or ECU that is at fault. I would suspect the motor in this scenario, but it could be either.
Motors come in two varieties. Brushless motors are the most common on modern E-bikes. They actually run on AC (alternating current) that is generated by the ECU from the DC (direct current) that the battery supplies. Plus, they are not run just by the voltage level, but by sine wave variations. Yes, complicated, but you don’t need to understand and design it, just find the bad component and replace it. Also they come in sensored and uncensored versions. Again, replacing the bad part is your only concern here.
A brushed motor is simple. You can feed the power from the battery directly and it should run. They have only two wires, where a brushless motor can have up to seven. Brushed motors have brushes that can wear out. They are pushed to a turning commentator with a spring. If the brushes wear too short, or the spring gets overheated, then the motor won’t run. If that happens, it will cause heavy wear or damaged that can’t be fixed. Also, the windings in the armature can fail. These motors are normally not too expensive to replace.
One other tip for brushless motor problems that I have been given by the technicians has never worked for me, but you might have better luck with it. Disconnect the wires at the motor for a few minutes. Reconnect them and try it again. Electrically separating the motor and ECU in this manner can set a reset into effect that has been known to solve the problem. Not for me yet, but maybe for you.
Some ECUs have built-in memories that store trouble codes. They will read out with light flashes that correspond to a particular problem. Once again, these have never helped me, and the erroneous codes they spelled out were useless. In each of those cases the ECU replacement is what brought the bike back to life. But they are there to help you and could tell you where to find the problem.
One problem you might run into, is that each E-bike electrical system is different. There is no set standard for them. One manufacture can use different systems on different bikes, and even in the same model run. I know that this fact can be discouraging, but the makers of E-bikes are coming up with better and more reliable electronics everyday, so problems are disappearing fast. The bikes just keep getting better and better all the time. That is encouraging.
I hope this has been able to help you. Remember that sight and feel can be your best tools. My visual examinations have found more problems than you could imagine. Many of the things that can go wrong are simple. And by all means, don’t get in over your head. Don’t make things worse by doing checks you don’t understand. And do it all as safely as possible.
Questions? Plus, I will revisit this subject as more info trickles in.
Keep that E-bike running well, Turbo.
“Bikes are a right livelihood.”—Scot Nicol.