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how do i diagnose this ?

how do i diagnose this ?

Old 10-30-2010, 09:48 PM
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Default how do i diagnose this ?

tues and fri practice...no issues
friday heat 1- 8 laps in throttle hangs wide open(with return spring on )
found receiver pack to be pretty much discharged(reedy 1600 mah) charged pack and only took 600 mah but i thought that was enough to get me through a 7 minute heat. hot laps ok..2nd lap throttle hangs wide open again. found heat shrink on receiver pack blistered and very hot. at this point i replaced the receiver pack. hot laps in the main, ok then 1st lap on the race throttle hangs heading into a jump. car leaves the track and runs about 50 or 60 yards and parks itself in the barn on the property.
after each failure the steering servo worked fine,the throttle did not work at all. i turned off the switch and tuned it back on and it worked fine.
receiver/radio is new(m11x) installed on thursday. servos are high tech 5990 tg.
how do i properly diagnose this problem?
ps : i spent about 2 hours on the bench today tapping on different parts of the car unable to duplicate...

Last edited by bpalmer; 10-31-2010 at 10:15 AM.
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Old 10-30-2010, 09:51 PM
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Originally Posted by bpalmer View Post
tues and fri practice...no issues
friday heat 1 8 laps in throttle hangs wide open(with return spring on )
found receiver pack to be pretty much discharged(reedy 1600 mah) charged pack and only took 600 mah but i thought that was enough to get me through a 7 minute heat. hot laps ok..2nd lap throttle hangs wide open again. found heat shrink on receiver pack blistered and very hot. at this point i replaced the receiver pack. hot laps in the main, ok then 1st lap on the race throttle hangs heading into a jump. car leaves the track and runs about 50 or 60 yards and parks itself in the barn on the property.
after each failure the steering servo worked fine,the throttle did not work at all. i turned off the switch and tuned it back on and it worked fine.
receiver/radio is new(m11x) installed on thursday. servos are high tech 5990 tg.
how do i properly diagnose this problem?
ps : i spent about 2 hours on the bench today tapping on different parts of the car unable to duplicate...


ethier the throttle spring went weak which happen to me before and that happen or the carb is sticking try to look at that.
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Old 10-30-2010, 09:54 PM
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maybe the servo is just bad are you on 2.4, and what he said about the carb sticking.
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Old 10-30-2010, 10:03 PM
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Originally Posted by RUNNINONMT View Post
maybe the servo is just bad are you on 2.4, and what he said about the carb sticking.
these servos have 400 oz of torque...if carb was sticking it would rip the slide right off. and when i cycled the on/off switch it went back to normal. yes it is 2.4
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Old 10-30-2010, 10:04 PM
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I had this happen when my on/off switch went bad. Throttle servo was all over the place when driving. Tried to bench test and nothing was wrong. Went back out, hanging RPM's. Direct plugged my receiver and it quit. The whole time the steering servo never glitched. I know that sounds weird but I haven't had a problem in months since it happened. Just something to check.
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Old 10-30-2010, 10:05 PM
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Originally Posted by bpalmer View Post
these servos have 400 oz of torque...if carb was sticking it would rip the slide right off. and when i cycled the on/off switch it went back to normal. yes it is 2.4
You posted this while I was typing. Yeah I think it could be your switch. Try to direct plug it in.
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Old 10-30-2010, 10:15 PM
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i had that happen to me three times. once it was a bad cell in the battery, once was the on/off switch and the other was receiver. try replacing the switch first and set it on your living room floor and play with the steering and throttle and see if it does it again. if it still does, try new battery and if it stilll does, re-bind your radio and receiver and set fail safe as full break and repeat. i did this for probably an hour one night on the floor trying to figure it out. it was the safe way of doing it since you dont have the engine running, but make sure its on the floor because it makes the steering servo work hard which pulls more power.
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Old 10-30-2010, 10:15 PM
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I have had 2 7955 do the same thing, after sending them back to hitec, they informed me the amps were on there last leg. hitec has awesome customer service. send them in and they will hook you up, and also that rx pack sounds like its smoked, which also indicates the amp may be going bad on you servo.
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Old 10-30-2010, 10:23 PM
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I had pretty much the same problem at a GCS race...Instead of going wide open, it would shut itself off. Checked the charge on the battery, seemed ok...I finally yanked the harness and found the connection between the battery and the harness was toasted....changed the harness and the battery and all was good.
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Old 10-30-2010, 10:25 PM
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Originally Posted by Do-Over View Post
I had this happen when my on/off switch went bad. Throttle servo was all over the place when driving. Tried to bench test and nothing was wrong. Went back out, hanging RPM's. Direct plugged my receiver and it quit. The whole time the steering servo never glitched. I know that sounds weird but I haven't had a problem in months since it happened. Just something to check.
I to agree with the bad switch problem. Had something similar happen at the last race that i was at.

Something more to think about. Did you possibly reverse the throttle servo after you went through the binding process with the receiver.

Just a thought, but you may want to at least rebind the receiver to the Tx with the breaks engaged so that the run-aways are minimized.
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Old 10-30-2010, 10:32 PM
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Thinking that the M11 2.4 might have a bug somewhere. Had a racing buddy have the same problem. Cost him 3 engines. Wondering if the amp draw from the servos is causing the rx to lose signal. I'd say re-bind and check and recheck your endoints. And ALWAYS have a fully charged battery.
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Old 10-30-2010, 11:50 PM
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Reminds me why I don't run a switch...
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Old 10-31-2010, 03:48 AM
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I have had similar problems but for me it was the servo that shorted out and draw HIGH CURRENT from the battery. The DX3S said the battery was empty right away. Disconnected it and it was fine again. As soon as the servo was connected the alarm went off again telling me the RX battery was empty.
You could have a short of some sort...
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Old 10-31-2010, 06:23 AM
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Originally Posted by mblgjr View Post
Reminds me why I don't run a switch...
same here took that crap off
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Old 10-31-2010, 08:28 AM
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Originally Posted by bpalmer View Post
these servos have 400 oz of torque...if carb was sticking it would rip the slide right off. and when i cycled the on/off switch it went back to normal. yes it is 2.4


Not true, A sticky carb can and will lock up if the carb goes sticky....Seen it before and had it personally happen a few time's dealing with a particular brand of motor's with shoddy carbs.....Check the linkage AT temp and at room temp and see if you feel anything.
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