Older VXL-3s, Intermittent (Uncommanded) Full Throttle

[Arise0185]

Hello everyone,

I recently picked up a Slash 4x4 VXL with an older Velineon VXL-3s system in it. I dropped in my "modern" Traxxas TQ receiver and calibrated the ESC endpoints, and everything seems to function as intended. However, I noticed that if the ESC cable comes loose from the receiver, the ESC sporadically goes into full throttle mode. Is this normal/expected behavior of this ESC? Is it possible I just have a bad ESC and will need to replace it?

To me, it seems the "fail safe" behavior should be to cut throttle when signal is lost, not go WOT

The ESC and servo plugs seem pretty loose. While this truck is in great condition from barely being used, I can tell the wires are fairly brittle and the tires are hard. Definitely experiencing the effects of "old age"

 

[slick2500]

The failsafe is in the receiver not the esc. This is a radio issue not esc. Someone probably turned off the failsafe.

TQ 2.4 Transmitter Fail-Safe Operation
When bound to the transmitter, the 2.4GHz Micro Receiver automatically
sets its fail-safe position to throttle neutral. This means the receiver will
automatically return the throttle setting to neutral in the event of signal
loss due to interference, low battery power, or accidentally switching the
transmitter off while driving. When powered on, the receiver’s green LED will
glow to indicate Fail Safe mode is active. If the LED glows red, the Fail Safe
mode has been deactivated. Use these steps to reactivate the Fail Safe system:
1. Switch the transmitter and receiver on.
2. Press and hold the receiver’s SET button. The LED will flash once, then turn off.
Continue to hold the SET button. After about three seconds, the LED will flash
on and off. It will continue flashing as long as you hold the SET button.
3. Release the SET button. The LED will now light green and glow steadily,
indicating Fail Safe mode is active.
Should you ever wish to deactivate the Fail Safe mode (for example, when
using a speed control that has its own Fail Safe circuitry), simply repeat the
steps above.

 

[Arise0185]

The failsafe is in the receiver not the esc. This is a radio issue not esc. Someone probably turned off the failsafe.

TQ 2.4 Transmitter Fail-Safe Operation
When bound to the transmitter, the 2.4GHz Micro Receiver automatically
sets its fail-safe position to throttle neutral. This means the receiver will
automatically return the throttle setting to neutral in the event of signal
loss due to interference, low battery power, or accidentally switching the
transmitter off while driving. When powered on, the receiver’s green LED will
glow to indicate Fail Safe mode is active. If the LED glows red, the Fail Safe
mode has been deactivated. Use these steps to reactivate the Fail Safe system:
1. Switch the transmitter and receiver on.
2. Press and hold the receiver’s SET button. The LED will flash once, then turn off.
Continue to hold the SET button. After about three seconds, the LED will flash
on and off. It will continue flashing as long as you hold the SET button.
3. Release the SET button. The LED will now light green and glow steadily,
indicating Fail Safe mode is active.
Should you ever wish to deactivate the Fail Safe mode (for example, when
using a speed control that has its own Fail Safe circuitry), simply repeat the
steps above.

Ah, thanks for copy-pasting the relevant portion of the manual! That's usually the first place I look, so I'm a little embarassed. This is the TQ manual I found on the Traxxas website, and interestingly enough the version I found does not contain the verbiage you quoted. Additionally, the receiver only has a "link" button, not a "set" button.

However, in this case, the ESC goes full throttle when the receiver is unplugged. Wouldn't this indicate that whatever is causing this behavior is in the ESC, NOT the receiver?

I did just test turning off the transmitter while giving throttle, and the ESC cuts throttle. So I think the failsafe is working properly, in any case.

For now I just replaced the ESC and servo plugs (used some cheap servo extension cables I had lying around and spliced them onto the original harnesses). Everything is nice and snug now, and at least they won't come loose while driving. Still don't exactly have the warm and fuzzies about the ESC behavior, though.

 

[slick2500]

Ah, thanks for copy-pasting the relevant portion of the manual! That's usually the first place I look, so I'm a little embarassed. This is the TQ manual I found on the Traxxas website, and interestingly enough the version I found does not contain the verbiage you quoted. Additionally, the receiver only has a "link" button, not a "set" button.

However, in this case, the ESC goes full throttle when the receiver is unplugged. Wouldn't this indicate that whatever is causing this behavior is in the ESC, NOT the receiver?

I did just test turning off the transmitter while giving throttle, and the ESC cuts throttle. So I think the failsafe is working properly, in any case.

For now I just replaced the ESC and servo plugs (used some cheap servo extension cables I had lying around and spliced them onto the original harnesses). Everything is nice and snug now, and at least they won't come loose while driving. Still don't exactly have the warm and fuzzies about the ESC behavior, though.

I found that on a random forum.

I have only ever seen that behavior from a faulty or improperly set failsafe. The esc is only supposed to apply throttle when the throttle command is sent via the receiver so maybe jiggling the wires around confused it somehow.