Servo getting HOT!

[Duxx]

BRXL, 3S Lipo, Castle BEC, 2 different Hitec servos.
I've swapped a hitec 7954sh and hitec 7950th and gotten the same result. I've wired the bec directly to the servo using a plug and ran the servo off the esc and gottent the same results. I've disconnected the servo from the plug and checked the voltage coming from the bec and it's a steady 7.4v. Here are the results I'm getting and the same applies to being wired straight to the bec as well as to the esc. Sometimes the servo stays cool and operates normaly. Sometimes it gets hot as hell, becomes unresponsive and eventually fails completely. I've done everything I can think of besides disconnect the servo from the truck and bench test it. I've adjusted the epa, checked the space between the servo horn and any other binding. I don't have a programmer so I guess that's one other thing I haven't done yet but I've gone through several servos that have all been repaired by Hitec and continue to get the same result. Am I overlooking anything else?

[Phins Fan]

I would have thought EPA but you said you addressed that. Can you post pics? Especially how the BEC is wired in. Or try disconnecting the BEC and run it for a bit without.

[Rook82]

Originally Posted by Phins Fan

I would have thought EPA but you said you addressed that. Can you post pics? Especially how the BEC is wired in. Or try disconnecting the BEC and run it for a bit without.

i would have thought that as well. Or that the servo horn is on too tight (binding), etc. Maybe during running as things shift, the servo horn binds to the servo body in some way over taxing it?

[braq]

hmmm, as you checked two servos it is unlikely they are the primary issue here. Can you check the voltage (or even better current, either directly if you have a multimeter with 20 Amps or using a shunt) while either one is running in the truck (under load, e.g. moving wheel against wall)? My guess is that the voltage drops (bec or battery being the cause) and therefore the amps go up.

cheers

braq

[Duxx]

Servo horn has plenty of clearance. I unplugged the servo and checked the voltage coming from the bec and it was a constant 7.4. Even with no load the servo begins getting warm after about 5 minutes of twitching the wheels back and forth. I'm gonna remove the tie rod and drag link today and begin process of elimination.

Scale beer cans, now that's the schlitz!

[bigstu]

Is this on a XR10?
I used to have heat problems with the stock steering linkage on my XR10.
Sounds like there is something that is binding up.
Disconnect the link at the servo and start eliminiating any areas of drag.

It is strange that just sitting there it gets hot.

[Duxx]

It's on a wraith with vp links. I pulled the links and servo horn off and tested it hooked to the bec and hooked to the esc. Similar results with both scenarios. Although it didn't seem to get AS hot, after about 5 minutes of twitching the wheel I could feel the servo getting warm.

Scale beer cans, now that's the schlitz!

[ittybitty]

Hey bud...just another process of elimination check...you've probably already done so...but just to be sure - with the servo disconnected from any linkage and without power can you move the horn easily throughout the range of motion...or does it have resistance?

[Duxx]

Moves freely. I'm running out of options here. I've got to be overlooking something though so I'm gonna test it several times without the bec in the equation. Try to find some consistency.

Scale beer cans, now that's the schlitz!

[filotr14lsdude]

What knuckles and c hubs?
I've just built up my sporty, the bushing I used in my king pins was a little tight. My servo got warm until I was checking steering and noticed the resistance from them bushings, so I freed them up and now it's no issue.

If your clutching at straws to find the issue have a look at this

[Duxx]

I'm stucking fumped guys! With no load, (no servo horn) connected straight to the bec via plug. After 5 minutes of twitching the wheel the servo gets to 110°. And when connected to the esc (no bec) I get the same result. The only constants in this equation are the battery, rx/tx and servo, although I've tested 2 different Hitec servos. I run the same setup in another truck with a JR servo without issue. Any other thoughts?

Scale beer cans, now that's the schlitz!

[bigstu]

5 minutes of constant back and forth and it only got to 110, call it good and move on.
I would have expected it to get a lot hotter than that.
I was running a S9157 on my XR10, when the kit first came out 2 years ago. With the stock steering, after a 4 minute course, I could almost not touch the servo it was getting so hot.
Pulled my IR temp gun, and it was running as high as 135 degrees, and on some days I didn't check it with the gun, I know it was hotter. It got to the point, I took the heat sink off a computer CPU I had laying around, milled it down, and installed it on the servo to help it cool during runs.
Ultimately the right thing to do was change to a different steeting tie-rod, ditched the 3-piece steering, and went to a smaller arm on the servo.

Just for grins, I might change out the BEC and see if that makes a difference. That is the only thing you haven't changed, correct?
Is the servo on the axle or CMS?

[Mtbingdrew]

Ive just bought a brand new berg v3, built it up with a HS-7950TH High-Voltage 7.4V Mega Torque Digital Servo and castle bec set @7.4v wired with the bec connected directly to the servo's red and black cable with its yellow cable connected to the rx.
I've used it for one 12min the first time (didn't pay attention to the servo) then ran it in my house over some cushions for 4min and notice the servo was very hot (measured with my ir gun @ 54 degrees Celsius) I believe you were talking in fahrenheit which would be 129 degrees. After reading this thread I'm lead to believe that this is likely normal. Probably why the heat shrinks on the servo are so pronounced.
With no servo connected my steering moves freely and my voltage from the bec is a constant 7.4v