My new Knight Hauler/Freightliner

[Backlash]

OK, the reason for the questions that I asked..

AND Yes, I'm thinking a power problem, but I'm leaning more towards a battery issue than a BEC one.. (However, a battery issue can cause a BEC issue)

Originally Posted by Backlash

Have you got the little limit switch connected up under the 5th wheel?

With the switch connected, the MFU supplies less power to the motor when running without the trailer than it does with it fitted..

Have you got another battery to try?

I was thinking that the problem could be low quality battery packs, and the voltage is dropping below the requirements of the MFU when the using full throttle in a high load situation (like with the trailer attached).. This battery issue COULD also contribute or cause a BEC voltage issue..

What exactly happens when it shuts down in top gear? Do you just lose drive, or do you lose everything (i.e. no steering, drive or gearshift)

Just wanting to get an idea if the MFU is going into a fault mode, (i.e. tripping out) or if it is the receiver/ radio gear..

Does it happen as soon as you select top gear, or can you drive it for a while?

Wanting to know if it could be heat related..

What do you need to do to reset the truck..? Is it just a matter of selecting 1st or second gear or removing the trailer, or do you have to turn it off, and then back on to get it to go again?

Wanting to know what you needed to do to get the truck going again..

Is your radio 2.4GHz, or crystal type (27MHz, 29Mhz or 40Mhz)??

Regarding your concern for no Aerial wire on the receiver.. No aerial is not uncommon in 2.4Ghz systems..

Have you used this radio with the MFC before?

Could the radio be faulty?? Do you have another known working Radio and receiver that you could swap into the truck and see if the problem still occurs??

Is it an MFC01 or MFC03?

Was not sure if the MFC-03 had an inbuilt LiPo cutoff.. I have heard of similar problems occurring with low quality batteries, and high power Brushless motors, and when the ESC has a LiPo cut off turned ON..

No disrespect to the others, but I just cant see how it could be just a BEC issue, when all that you are doing is moving to full throttle in top gear..

HOWEVER, I could see it being a battery issue, where the additional load from the trailer and top gear is causing the battery voltage to momentarily drop below the requirements of the MFU's inbuilt BEC, and thus causing the MFU and radio to "stutter" and stop..

Much of this fault finding is a process of trial and error.. Here are some things that you can try (ONE AT A TIME)..

*If you have another working radio and receiver, try that instead of the Tamiya/Futaba unit..

*If you can borrow another battery off someone to try..

*If your using NiCd or NiMh batteries, and cant borrow another to try, completely discharge one of the batteries that you have, then put it on the charger (fast charge) and then put it in the truck as soon as it finishes charging and try that.. The voltage of a freshly charged battery will be slightly higher than one that has been sitting for a while.. (NOTE. DO NOT do this for LiPo batteries)

*If you think that it could be related to the MFU's BEC, then Disconnect the shift servo (and any other servo's or lights that run off the BEC) and leave ONLY the MFU and steering servo connected.. Manually move the shift servo into 3rd gear, and give it a test run..

*You could try a "stutter stopper" connected to one of the receiver ports, or via a Y lead.. Basically a "Stutter Stopper" is a capacitor that connects in parallel with the BEC.. Capacitors are devices that store a charge, and then can discharge it very quickly into a load.. With the Stutter Stopper connected, it will help to keep the BEC voltage at its correct level.. If you don't have, or cant buy a stutter stopper, you can make one from a 16V 4700 uf (micro Farad) electrolytic Capacitor, and an old servo lead.. Electrolytic Capacitors are polarity conscious, so connect the positive to the RED wire (for Futaba leads) and negative to the Black (for Futaba) and discard (remove/don't use) the white wire..

Mark..