Hi and
![](https://i.imgur.com/evDSMvT.png)
to the forum.
Unfortunately, there is very little information on the BAC-0501 controller, but I did find a photo showing most of the important connections:
![](http://www.arhservices.co.uk/GoldenMotor/BAC-0501%20controller_zpsyzrvbzmy.JPG)
![](https://www.goldenmotor.com/e-Bike-DIY/BAC-0501.jpg)
Referring to the above image, the 5V terminal below C on the 12 pin connector does not have 5V present on it. Do I need to inject 5V, or is the controller supposed to output 5V on the terminal?
Both of the +5V terminals should have ~5V output from the controller when the controller is powered on, if you don't have ~5V on either terminal, it is likely that the controller's integrated +5V regulator chip may have failed.
If this is the only part of the controller that has failed, applying an external +5V source should make the controller work again.
You should be able to test it using three AA batteries connected in series, but a
simple DC:DC converter could be used as a permanent solution if the batteries allowed the controller to work again.
![](http://www.arhservices.co.uk/GoldenMotor/emoticons/fingerscrossed.GIF)
However, if more of the controller's electronics have failed, it is not going to be easy to find the cause of the problem without a detailed circuit diagram of the controller's board, and I have not come across one of those yet.
I have measured this terminal with L and B+ connected, and with L and GND connected (which is how my vehicle seems to have been wired) but still no output.
According to the picture I posted above, the L terminal should be connected to B+ to activate the controller
(not to GND)I also seem to recall someone mentioning on these forums that XS1 and XS2 can have a buzzer plugged in for status info, has anyone tried that?
I just saw https://goldenmotor.com/SMF/index.php?topic=448.0 and the corresponding diagram posted by Tom, am I right in saying that for the BAC-028 I need to connect B+ to GND?
I don't recall seeing one of these controllers with a horn connected like the BAC-028 controllers had, so I don't know if this controller uses the same beep codes for diagnostic purposes.
With the BAC-028 controllers it was necessary to connect the B+ to the "Gate" terminal
(labeled "G" not "GND") to enable the controller.
![Wink ;)](https://goldenmotor.com/SMF/Smileys/default/wink.gif)
Please let us know if the controller does work correctly again with an external +5V supply.
Alan