View Full Version : AWD ra-23T stock 3010 fets cuts out when 50T motor gets hot

2013.02.27, 12:41 AM
Just built a brand new AWD up, previously ran 70T with am boards no issues, wanted to upgrade to ASF and get a faster motor so I checked out reviews of the 50 turn bearing PN and everywhere i saw said it was safe on stock fets.

i bought a brand new RA-23 and installed it and to be safe i added in a 3Racing aluminium vented motor cover and air dam to keep it cool.

unfortunately on my RCP track at home, it gets pretty hot pretty quickly and cuts out power to the motor - of course steering is fine.

2 minutes later, taking off the body etc and blowing on the board and motor and the board is just fine and then everything is good to go again again.

there's no thermal shutoff like on the older motor wires.

my question is..

does anyone else run into problems with this board and this motor combination ?

im going to go back down to 70T in the meantime but all advice appreciated :-)

I dont want to burn out my fets and then have to replace them..

i have an ra22 in an MR-02 with a 50T and that is just fine, never cuts out or even thinks of overheating.

2013.02.27, 07:05 AM
The drivetrain friction is enough to place a higher load on your electronics but I run an xspeed AWD in mine without fault on stock fets.

I have not had thermal shutdown issues with any RA-22/3 board though...

2013.02.27, 09:41 AM
Ditto on the drivetrain friction... make sure everything is operating as it should, gear mesh is good, diffs operating properly, no wheel-bind, motor bushings/bearings oiled, armature is aligned, etc...

Worse-case scenario, you may have a fet foot that needs a tap with a soldering iron. I've had this before, a loose solder connection from stock that only became disconnected when the thing heated up. It's rare but it does happen.

2013.02.27, 03:30 PM
Thanks for the info guys, I really don't want to be down a brand new board if I can possibly help it., I will check the FET feet on both sides ( top and bottom)tonight.

I put in new gears yesterday and checked the mesh, I was also worried it was overgeared to start with causing extra heat.

the RCP big L I have at home I can almost drive round at full throttle non stop, so It's likely also causing some excessive heatbuild up.

even with the body off ( where it should get better ventilation it still cuts out.

I checked my ball diff was smooth and I also took out the motor and ran the chassis across the floor to check there was no tightness or noises or unexpected binding as all four wheels are turning.

the motor is brand new bearing type- I did not "run it in" first though.. perhaps this is part of the issue, it's defo the motor that is hottest and stinky. it runs pretty smoothly when turned manually and also out of the gears, no noises- but there is defo more braking / resistance to turning when turned manually compared to other motors I've had though.

I will probably open it tonight to check the condition of the armature and the brushes ( should've done that last night perhaps...)

I'm worried the thermal shutdown is because the heat off the motor is rising up into the FET's on the bottom side of the board, since this new board is short in length, I'm going to mount it on the other side of the board mount socket closer to the front of the car , out of the line of heat rising from the motor and see if that makes a difference, I've also removed the top cover for the board too.

since I have another 50T in my mr02 I'll try swapsies as well and see if I can isolate this to the motor or the board in the AWD. diff motor same board cutout = board issue and especially if the new motor does not cause the other board to cutout.

will keep you posted.

2013.02.27, 03:33 PM
yeh the X speed is a bushed 50 turn so the pnwc 50 turn bearing should be ok too.

I will defo check for dry joints on the fet legs too.

2013.02.27, 03:58 PM
the RCP big L I have at home I can almost drive round at full throttle non stop, so It's likely also causing some excessive heatbuild up.

Uhhhh.... no, not good.

You shouldn't be able to even come close to full throttle on a short track (aside from very short bursts), something is definitely binding up! Either that or your throttle trim is turned way down.

2013.02.27, 04:45 PM
A 50 turn in an AWD should give pretty good speed. What pinion/spur combo are you using?
I wasn't aware the electronics had a thermal shutdown feature, I'm going to have to test that.

2013.02.27, 05:58 PM
I don't know where in NorCal you are since it's a huge region but if you can drop by AutoMicro in Santa Clara or Inside Line Racing in Cupertino, I'm sure either place will have no problem with taking a look at your car :)

2013.02.28, 12:53 AM
so im running the 4.5 - 5.5 ratio gearing recommended for the motor

it's an a2/ b2 spacer and the 21 x 27 combo

i stuck the AWD and 50t on the speed checker, it's got a bearing kit all round on everything too, so friction should not be an issue, and i was getting approx 29kph, it did not seem like it was binding anywhere drivetrain wise.

i also removed the receiver cover to let in more air and then ran it without the body round the track

I do seem to be on full throttle for .5 to 3/4 of the lap though so after about 5 minutes it cut out again.

the fets initially seemed hot, but then i popped out the motor and only it was really hot.

i swapped in the original 70 t very quickly after it cut out and it ran and ran with no real issue over the same period on the track ( not a surprise as it maxes out at 16kph on the sped checker so doesn't pull anywhere near the same current as the 50T)

when i get some more time this weekend I will try out some more stuff and will keep you updated, thanks for the help and advice.

san jose is 2.5 hours away, just dont have that amount of free time to go there.

Thanks guys.

2013.02.28, 01:07 AM
Your gearing seems way too aggressive to me, especially for the the size of the track. I'd give the factory gearing a try and see how it does.

2013.02.28, 01:15 AM
Thanks TheSteve, I just noticed the same thing when i looked at the pn gearing chart again hoping i'd missed something. When i re-read the recommended gearing it's actually 4.8-5.5, not 4.5 as i said earlier.

I've now got in the 19/29 to make it 5.34:1 and I will try it out tomorrow.

will keep you updated, many thanks !

2013.03.01, 01:24 AM
Thanks guys !

I have found some binding at the front between the atomic I.A.S top plate to my front diff case.

i installed the I.A.S on a new sp chassis and when i placed the diff in, originally there was no noticeable wear on the diff cover.

i'm using the std awd diff at the front and a ball diff at the back, in my investigation of the issue I already took the rear diff apart and re-greased it, but when i went to look at the front one tonight..

i then noticed the binding between the top cover and the side of the diff, the teeny black diff cover screws had worn down to silver and both the diff case and the top cover were noticeably marked

i therefore shimmed a new diff across a tiny bit and xacto knifed some of the offending mating surface fron the I.A.S top cover and voila, no more binding.

i will try it out this weekend and update if resolved.

Thanks again.

2013.03.29, 09:40 AM
Are you still running the PTC on the motor line? That is the Yellow Brown square component. It is a thermal reset fuse.

2013.03.29, 06:27 PM
If your able it help to put 4 fets above and 4 fets below and make sure the car rolls freely when you remove the pinion and if available get the ATM Chilli or ATM Stock R motor those motor run the coolest. And yes that yellow/brown square thing shut the car down if it senses to much heat. 5.34 final ration may create a little more heat mine with the chilli is geared at 15/31 7.2, 16/31 6.7 or 17/31 6.2 I prefer the 15/31 or 16/31 at our track.

2013.04.24, 06:16 PM
hi guys, sorry for the delayed reply I did not know you guys had posted on this.

im still struggling to get time to spend troubleshooting this further., but I wanted to say I did not have a thermal fuse on the pn 50T motor ( no caps either) , I do have one on the old stock motor, so I know what they are :-)

I will try out the gear ratios you suggest, that is perhaps exactly what I need to try to keep it cool(er).

I took off the motor pinion and pushed it, there still seems to be LOTS of friction from the rear diff, so im going to double check that .

I removed the rear completely and the front diff, to pinion to centre driveshaft is pretty frictionless, so i'll try out the gear ratios and check the diff and will update you on my progress.

Thanks very much for the info and ratio data guys.