# SEVCON GEN4 info



## Iguanaman309 (9 mo ago)

Hello all, new to forum, recently acquired a small ev vehicle, no nothing about it and manufacturer out of business, so not any luck getting info. It has a Sevcon Gen4 controller pack with converter and solenoid mounted on large heat sink. Batteries hold a full charge (48v), when I turn on key solenoid clicks on, get a single green power light on controller, but nothing else happens, when I flip the switches for direction, speed etc. nothing happens other than I hear ice cube relays under dash clicking. The only Difference I ever see is if I turn on key or flip a switch with pedal depressed, then I get an error (sequence ) with 2 flashing lights, otherwise no error messages at all. Question is how can I troubleshoot this? it has a 3 phase motor, what voltage should I get to motor?how can you test the motor, I have tested the pedal and it gets the proper reading, and since I’m not getting any error messages I’m assuming maybe motor isnt working? I’m stuck, Amy help would be greatly appreciated, thanks in advance. I am electrically and mechanically minded, just never messed with EV vehicles before.


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## floydr (Jun 21, 2021)

A photo of the EV might help, even the name and model would help. The people here on the forum are pretty good at troubleshooting.
later floyd


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## cricketo (Oct 4, 2018)

That sounds to me like a throttle problem. That sequence error is correct if there is an interlock (micro switch) on the throttle. Double check the wiring from the throttle to the controller, if nothing stands out, open up the throttle and share the pic of the wiring here. I suspect it's a hall effect throttle, so there will be 3 wires - once we confirm that, we can try to diagnose it with a multimeter.


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## Iguanaman309 (9 mo ago)

Here are some pics of the vehicle, it’s a Titan side by side 4x4, sniper E4, it is kind of buried in my garage at the moment.










cricketo said:


> That sounds to me like a throttle problem. That sequence error is correct if there is an interlock (micro switch) on the throttle. Double check the wiring from the throttle to the controller, if nothing stands out, open up the throttle and share the pic of the wiring here. I suspect it's a hall effect throttle, so there will be 3 wires - once we confirm that, we can try to diagnose it with a multimeter.


Thanks for your response, the throttle has a 5k on pot in it and a micro switch, pot ohmed out good but I replaced it anyway, microswitch checks out too, I haven’t checked wiring from throttle to controller yet, I did find a sevcon manual with a generic wiring diagram to give me some idea, I want to say the plug has 4 wires to it (the throttle), and I have checked it from throttle to connector, but not from connector to controller. I have added some pics of the vehicle to the post but everything is pretty crammed in there so not sure how helpful they are, I can add a pic of the inside of the throttle, I do have it removed at the moment if that is helpful. i Am only getting that sequence error, when I first got it, batteries were low, but when I turned on the key the dashboard lit up correctly but vehicle did nothing, I plugged in the charger(on board) and batteries have held a constant 48volts since but the dash no longer has info, just backlight.


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## cricketo (Oct 4, 2018)

Okay, so the next thing I'd suggest is unplugging the 35 pin connector from the controller, and measuring your throttle pot between pins 22,34 or 23,35. Sevcon provides for two throttle inputs, I suspect only one will be used in your case. So that should confirm if your wiring is correct. Also pot's other side is tied to the bat-, check that it's good.

Is there anything that looks like a Vehicle Control Module, or all the inputs terminate directly into the Sevcon ?


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## Iguanaman309 (9 mo ago)

cricketo said:


> That sounds to me like a throttle problem. That sequence error is correct if there is an interlock (micro switch) on the throttle. Double check the wiring from the throttle to the controller, if nothing stands out, open up the throttle and share the pic of the wiring here. I suspect it's a hall effect throttle, so there will be 3 wires - once we confirm that, we can try to diagnose it with a multimeter.


There are 5 wires on the plug, a blue and yellow that go to the microswitch and a brown, black ,red that go to the pot. The wires are numbered on plug but dont seem to correspond with any numbers on wiring diagram.

























cricketo said:


> Okay, so the next thing I'd suggest is unplugging the 35 pin connector from the controller, and measuring your throttle pot between pins 22,34 or 23,35. Sevcon provides for two throttle inputs, I suspect only one will be used in your case. So that should confirm if your wiring is correct. Also pot's other side is tied to the bat-, check that it's good.
> 
> Is there anything that looks like a Vehicle Control Module, or all the inputs terminate directly into the Sevcon ?


There is another module below the contactor but not sure what it is, otherwise they alll seem to go to the controller.


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## cricketo (Oct 4, 2018)

Those numbers are specific to the vehicle, and don't matter since you don't have a wiring diagram. 3 of them are for the pot - two should have continuity with the numbers I called out on the 35-pin connector, and one should have continuity to the B-


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## Iguanaman309 (9 mo ago)

Did some ohming of the wires, does go across 22 and 34, when going from middle lug on pot to m- I get nothing, I jumpered a wire from m-to center lug, then get my 5 k reading at pot, wires ohm out good from plug to 35 pin connector, but don’t ohm to 22 and 34 unless I wiggle the connector around, so maybe that is my issue? The throttle plug barely reaches through the firewall so I will have to figure out how to get to it and bypass the plug, issue seems to be from throttle side plug. Should I try to bypass or get another throttle assembly?


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## cricketo (Oct 4, 2018)

Iguanaman309 said:


> Did some ohming of the wires, does go across 22 and 34, when going from middle lug on pot to m- I get nothing, I jumpered a wire from m-to center lug, then get my 5 k reading at pot, wires ohm out good from plug to 35 pin connector, but don’t ohm to 22 and 34 unless I wiggle the connector around, so maybe that is my issue? The throttle plug barely reaches through the firewall so I will have to figure out how to get to it and bypass the plug, issue seems to be from throttle side plug. Should I try to bypass or get another throttle assembly?


what is m- ?

Judging by the last picture you have heavy oxidation on the contacts in the connector. I'd recommend cleaning that up before testing.


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## Iguanaman309 (9 mo ago)

So removed plug from throttle assembly to 6 pin going to 35 pin, I replaced with spade connectors, all wiring ohms out from throttle to 35 pin connector, I get the changes when the throttle is pushed and get my 5 k readings when throttled moved back and forth, but still the same issue, another issue I have is all the switches 
on here, I have one the only says “F” on the top
, it’s a 3 way switch so I’m guessing that’s forward or reverse, then I have a 2 wd/4wd switch, then a lo/high switch, dash also has a small push button that I can’t tell where it goes, I have tried every combo I can think of with these switches, still only get the 2 flash error when I push down on the throttle.


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## cricketo (Oct 4, 2018)

It's going to be a difficult one without hooking up a computer to the motor controller. 2/4wd switch probably doesn't go to the Sevcon, but instead either goes to some Vehicle Control Module, or just some relays and eventually transmission. F/W and H/L are likely wired to digital inputs on Sevcon, I imagine only really F/W matters - how many wires are on H/L ?

So with F/W check if you're getting a connection in both positions between B- and pins 18 (digital 1) and 30 (digital 2). H/L may give you something between B- and pins 9 (digital 6) and/or 32 (digital 7). Then another thing to double check on is parking brake - that one will likely be "normally closed", so when brake is released check B- to pin 20 (digital 5). Double check your interlock (microswitch in the throttle) on pin 19 (digital 3)

Those pin assignments are "typical" per Sevcon documentation, but they can be arbitrary otherwise. So if anything doesn't seem to ring properly on those pins, you may have to try every other option, including pin 21 (digital 8) and pin 31 (digital 4). 31 is mentioned as a seat switch, do you have one ?

I have a buggy similar to yours, when I release the parking brake main contactor clicks, until then the controller is only powered through the keyswitch. Does yours do that ?


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## Iguanaman309 (9 mo ago)

cricketo said:


> It's going to be a difficult one without hooking up a computer to the motor controller. 2/4wd switch probably doesn't go to the Sevcon, but instead either goes to some Vehicle Control Module, or just some relays and eventually transmission. F/W and H/L are likely wired to digital inputs on Sevcon, I imagine only really F/W matters - how many wires are on H/L ?
> 
> So with F/W check if you're getting a connection in both positions between B- and pins 18 (digital 1) and 30 (digital 2). H/L may give you something between B- and pins 9 (digital 6) and/or 32 (digital 7). Then another thing to double check on is parking brake - that one will likely be "normally closed", so when brake is released check B- to pin 20 (digital 5). Double check your interlock (microswitch in the throttle) on pin 19 (digital 3)
> 
> ...


Thanks for the help! Mine the main contractor clicks when you turn on battery, I will have to check the parking brake as the handle is frozen and won’t move, but brakes are off, maybe that’s my sequence error, the h/l and f/r do go to ice cube relays that trip when switches are toggled. I will check out the other stuff too, so parking is n/c until released?


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## cricketo (Oct 4, 2018)

Iguanaman309 said:


> Thanks for the help! Mine the main contractor clicks when you turn on battery, I will have to check the parking brake as the handle is frozen and won’t move, but brakes are off, maybe that’s my sequence error, the h/l and f/r do go to ice cube relays that trip when switches are toggled. I will check out the other stuff too, so parking is n/c until released?


Right, safety systems typically utilize "open circuit" as the safe condition. Basically when parking brake is engaged, circuit is open and vehicle won't move. But if the wire is broken to the parking brake switch, vehicle will also think that parking brake is engaged and won't move. Only when the circuit is closed it will be considered as parking brake is disengaged. The other thing is sometimes a number of sensors/switches can be wired in series, as opposed to like "typical" situation for the Sevcon described earlier. So like parking brake may be wired in series with the seat switch, and both have to be closed for vehicle to move, that's on a single digital input of the motor controller.


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## Iguanaman309 (9 mo ago)

cricketo said:


> Right, safety systems typically utilize "open circuit" as the safe condition. Basically when parking brake is engaged, circuit is open and vehicle won't move. But if the wire is broken to the parking brake switch, vehicle will also think that parking brake is engaged and won't move. Only when the circuit is closed it will be considered as parking brake is disengaged. The other thing is sometimes a number of sensors/switches can be wired in series, as opposed to like "typical" situation for the Sevcon described earlier. So like parking brake may be wired in series with the seat switch, and both have to be closed for vehicle to move, that's on a single digital input of the motor controller.


Sorry, haven’t had time to mess with it, I did find the parking brake switch disconnected, my brake light switch is bad but only seems to control the lights, my parking brake switch does work, now when I release the parking brake, turn on fwd switch and step on throttle, I don’t get the sequence error, but still no motion, do you happen to know what voltage I should be getting at M1, M2 and M3 when throttle is pressed? I’m wondering if my motor is bad, or some way to test the motor without the controller to see it it’s working?


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## cricketo (Oct 4, 2018)

you can measure between any pair of M wires with a multi-meter on AC setting, you should see non-zero voltage if there is some output. Now the deal is controller likely wouldn't be happy if it's applying voltage yet getting no feedback from the encoder, so I doubt there is any output. I think without a sequence error it's back to the interlock and/or throttle output.


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## cricketo (Oct 4, 2018)

The other thing I forgot to mention... Sometimes throttle has two sensors in it, and the Sevcon can be configured for dual throttle input. It uses the two sensors for redundancy and the outputs have to properly align or it won't budge.


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## Iguanaman309 (9 mo ago)

cricketo said:


> you can measure between any pair of M wires with a multi-meter on AC setting, you should see non-zero voltage if there is some output. Now the deal is controller likely wouldn't be happy if it's applying voltage yet getting no feedback from the encoder, so I doubt there is any output. I think without a sequence error it's back to the interlock and/or throttle output.


Ok I’m going to check voltage again, if I remember right I was reading like 24 volts ac across the M’s, but I may be mistaken.


cricketo said:


> The other thing I forgot to mention... Sometimes throttle has two sensors in it, and the Sevcon can be configured for dual throttle input. It uses the two sensors for redundancy and the outputs have to properly align or it won't budge.


so I’m not getting any ac voltage across m’s, I always have dc voltage going to controller from contractor even though I hear it cycling, but power light comes on and off with key, today found the seatbelt switch doesn’t work, thought I had an “aha” moment, but jumpered when turning on or open when turning on makes no difference in green light, stays solid, only gives sequence error if I turn on “f” switch before releasing parking brake, I am getting my 5k reading from throttle, switch is working, when I turn on key, contactor Trips but no voltage change, always has 48 v dc to controller lug from contractor. This thing may have me beat, lots of corrosion in wiring, but all electrics work, tilt bed, lights, winch, controller powers but that’s about it, dash lights up and has a battery symbol on it but nothing else, just a lot going on to figure out, I’ve seen people on YouTube do a ”simple “ bench hook up with a motor for a motorcycle, maybe I need to pull everything out and try that, but seems like a lot.🤷‍♂️


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## cricketo (Oct 4, 2018)

Yeah, it's a lot of poking in the dark unless you can hook up the computer to it and see what's up. Some EV companies have a rental program, maybe you should do that next.


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## cgunzelman (3 mo ago)

I just picked up a gokart with a Sevcon Gen4. I believe pin 19 on the 35 pin connector needs to be connected to ground (or B-) just after power up with the Fwd & Rev switch in neutral if possible.

2 blinks of the status light can mean lots of different things, check the fault table near the end of the manual.

These controllers have safety inputs that can be programmed A LOT of different ways, so my setup is likely different than yours.

Just relaying what little I know. Was in the same boat as you a few weeks ago.


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