G3M20211-1592-16 controller with new 790 ebike display


New Member

Thanks for letting me join the forum. I converted an old bicycle back in 2011 with a 36 v conversion kit and have been enjoying riding the bike ever since. But lately I have had to change a few parts due to weather taking its toll. And it is here I was wondering if anyone could help me with a problem. I had to change the ebike display next to the handlebar as it had got moisture inside. The old display had no text at all, but I was able to open it and found the text 790xxx on the print board and as a search online showed several similar displays with the text 790, I hoped one of this would do the trick. But after installation of new display I notice that it does not work as before:

Mode 0 (No LED) = No pedal assist
Mode 1 = No pedal assist
Mode 2 = Pedal assist as in mode 1 on the old display
Mode 3 = Pedal assist as in mode 2 on the old display

This means that I am not able to activate the Mode 3 full pedal assist, which I miss at times in hilly Norway:) On the old display I could switch between the pedal assist and throttle using a button named "Switch", but on this display it is called "Light" and has no function as the throttle work all the time and I have then been able to have full pedal assist holding the throttle down, but it is of course a bit tiresome. I will also mention that I change the batterypack last year to another 36 V, but assume that should not change any of this logic between the controller and display ?

I did some measurements last night on the wiring between the 790 display and the G3M20211-1592-16 controller (voltage measured between Red wire and the others):
Red = VCC (41 v)
Yellow = Light ON (0V) / OFF (41V)
White = 41V
Blue = ON (0V) / OFF (41V)
Black = GND (41V)
Green = Pedal assist:
0 LED = 41 V
1 LED = 40 V
2 LED = 39 V
3 LED = 38 V

The controller is as stated an old G3M20211-1592-16 manufactured in dec 2011 and has a black enclosure, but I see the same controller can be purchased still, but then with a aluminum enclosure and according to this site, it should operate fine with 790 ebike display I bought:

One other detail, the new 790 display did not have the same connector as the old one (round), but as the wire colours was the same I did just cut the new square connector off and used the old (soldering).

If anyone could shed any light on this problem it is much appreciated!

Best regards,