Mystery Glitch Driving Me Crazy!

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MonsterAir

MonsterAir

Lone Racer 🤠
Messages
2,369
Location
Long Island NY
What's up guys. I'm hoping someone can help me out before I jump out a window here. I have an FG Marder and keep experiencing this random/intermittent glitch that locks up my servos causing runaway type of issues. For the most part my super bee will kill it right away but sometimes the kill switch won't catch it and off it wants to go. Again it does it kinda when it wants to, I've have times where it doesn't happen like in my recent vid but then days like yesterday it just wouldn't stay running without an issue. Ok so that's the story and this is what I have done about it so far......

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Problem seems to be an engine interference issue because it only happens when the motor is running. So I've raised and shrink wrapped my throttle linkage and put a fuel line over the brake linkage because they do touch the engine. I've lined my throttle brake servo w/ electrical tape so the servo isn't sitting on the alloy plate. I've also got a cap run to one of my aux for my power hungry Savox.

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Here are a few pics of the mess of wires I have running into my radio box. The throttle servo's wire is run on the backside of plate zip tied. Could this birds nest be the culprit?

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Lastly is the super bee. I have it tucked behind the pull start cover. Not being hit by any fins or in the way of anything but def touching the engine. My thought was it's protected by that interference filter but now I'm starting to rethink that.

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If anyone has any insight into what might be causing my nightmares I'd be so grateful. Thanks
 

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I was just thinking back to my last few runs. Ran on dirt with no issues 2 or 3 times then brought her down to the beach and began experiencing the issue more frequently. Different day diff beach no issues (vid I posted) then diff day diff beach full of glitching issues after about 10min and now she's glitching at start up or when I give throttle it will lock up. This last beach run I didn't hose her down with air, could sand be causing this? I guess I'll wipe her down and find out.
 
Hmm. Sand was a bit softer but I would think my cap should be preventing any sudden voltage drop from glitching the servo plus that wouldn't explain why yesterday she was doing it on start up. When I could get it to idle without shutting off it would glitch when I gave gas. Battery was at 4.05v per cell.
 
Al, you got me thinking...... Those dirt runs were on a fresh battery and I haven't charged since. Being my voltage is higher then 4v per cell I didn't think I had to. Ya think my new Savox is sucking the voltage down? I'm running a 6000mah killer rc 2 cell lipo and usually charge when each cell hits under 4v, my charger says it puts around 1200-1500 mah into the battery after completion.
 
I am unfortunately running a spektrum dx4s and the servos are Hi-Tec 7980th and Savox 0241mg. Trebor I have tried changing plug more then once. I have also recently changed the ignition thinking that was the reason but nope just wasted $40
 
I guess I'm gonna fully charge the battery and if it keeps doing it unplug the savox to see if thats the culprit. Will report back with a video when it cools down a bit later on in the day. Yanking that cord under the 85deg sun we have here today doesn't sound all that fun lol.


Oh ya..... nitrocat, if you stop in for a look. I tried turning the wheel hard back and forth while holding full brake and no glitch. This was while the motor was off. Which again makes me believe it's a motor interference issue.
 
Turns out the avc function on my sr4210 receiver is busted. Called specktrum support and the guy walked me through disabling the avc function. Apparently even though avc is technically inactive on the transmitter it is actually on unless you have a second bind plug in the disable port. I'm sure it says it in the manual somewhere but then why have the setting on transmitter to disable it? At least I didn't have to wait on hold, they have a nice call back option. Every company needs that feature!
 
Any suggestions guys? I'm about to give up and switch over to electric here. I could really use someone to help me go over every possible cause of interference. I'm lost as where to start next. KillerRc says the way I have the kill switch is fine but I went ahead and ordered an extension pack anyways to try running it around the motor. Servos seem to be fine, no glitching when motor is off and everything functions as it should. Turn the damn motor on and it starts to dance. I've gone all summer with 10min runs if that. Never even gone through a full tank. Car runs great otherwise.
 
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MonsterAir said:
Any suggestions guys? I'm about to give up and switch over to electric here. I could really use someone to help me go over every possible cause of interference. I'm lost as where to start next. KillerRc says the way I have the kill switch is fine but I went ahead and ordered an extension pack anyways to try running it around the motor. Servos seem to be fine, no glitching when motor is off and everything functions as it should. Turn the damn motor on and it starts to dance. I've gone all summer with 10min runs if that. Never even gone through a full tank. Car runs great otherwise.
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Faulty insulation on plug wire ???
 
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I'm using the ngk cr7hix and cr8hix. But I''ll give that plug a shot. Is there any way to ground the plug to stop interference? I was searching the web and noticed the airplane guys seem to get this problem a lot. One guy said he sodered a wire to the plug and cnnected to the engine and it stop the issue for him.
 
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So it seems that my problem lies in the throttle brake linkage. I removed servo horn and disconnected brake and throttle linkages and now no more glitching in the servo. Battle won but the war goes on! My new try is going to be fitting a antennae tube over the throttle linkage but if anyone has another idea I'm all ears.
 
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