# Gem won't go into reverse
**URL:** https://community.electricforum.com/t/gem-wont-go-into-reverse/6022
**Category:** GEM Forum
**Created:** [May 8, 2016, 7:32am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022 "2016-05-08T07:32:58Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@glassact](https://community.electricforum.com/u/glassact)
#### Post date: [May 8, 2016, 7:32am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/1 "2016-05-08T07:32:58Z")
Folks -
I have a GEM E2 with a T3 controller. The aftermarket motor on the car recently burned up, requiring me to replace it with the original 5hp GE motor. The car now runs fine in forward gear,but gives a 66 error code immediately upon any attempt to back up. Does anyone have any idea what might be the problem, and how it might be repaired?
Thanks in advance - Ed
---
### Author:  [@Inwo](https://community.electricforum.com/u/Inwo)
#### Post date: [May 8, 2016, 9:37am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/2 "2016-05-08T09:37:12Z")
The car reverses by reversing the field.
Control uses a separate set of transistors for forward and reverse.
IMO one or both of the rev. field transistors are shorted.
---
### Author:  [@glassact](https://community.electricforum.com/u/glassact)
#### Post date: [May 8, 2016, 9:55am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/3 "2016-05-08T09:55:33Z")
That was my guess. Where are the field transistors located, and are they easily replaced? If not -does the controller need a rebuild?
Best - Ed
---
### Author:  [@Inwo](https://community.electricforum.com/u/Inwo)
#### Post date: [May 8, 2016, 10:18am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/4 "2016-05-08T10:18:32Z")
Are you up for board level repairs?
I’ve had success with this. Change all four if you do it yourself.
---
### Author:  [@glassact](https://community.electricforum.com/u/glassact)
#### Post date: [May 8, 2016, 10:27am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/5 "2016-05-08T10:27:00Z")
No problem there. Are there schematics available, and part numbers?
Best - Ed
---
### Author:  [@Inwo](https://community.electricforum.com/u/Inwo)
#### Post date: [May 8, 2016, 11:09am UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/6 "2016-05-08T11:09:59Z")
Not that I know of.
Parts have good markings to cross reference.
When you open control, it’s obvious which TO-220 devices connect to field terminals.
Will show dead short on bad one. Compare all four.
If no numbers, I’ll share the ones I use.
STP80NF 12
MOSFET N-ch 120V 80A TO-220
---
### Author:  [@glassact](https://community.electricforum.com/u/glassact)
#### Post date: [May 13, 2016, 4:43pm UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/7 "2016-05-13T16:43:47Z")
Received the parts from M\*\*\*\*\*, and replaced the bad transistor. I’m not receiving a -51 error, and when I check the voltage at the + and - end of the controller, I’ve no power. The fuses (particularly F13) are fine, and all 12 volt functions work. Any idea what else might be blown?
Thanks in advance - Ed
---
### Author:  [@Inwo](https://community.electricforum.com/u/Inwo)
#### Post date: [May 13, 2016, 6:06pm UTC](https://community.electricforum.com/t/gem-wont-go-into-reverse/6022/8 "2016-05-13T18:06:58Z")
Still run forward?
If not, retrace your work. Something changed.
You won’t have power on B+ at control until master relay pulls in.
Controller logic must be happy for that to happen.