Exhaust Valve Actuator Dissected - MVAgusta.net
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post #1 of 6 (permalink) Old 07-02-2019, 10:38 AM Thread Starter
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Red face Exhaust Valve Actuator Dissected

Since I had a MV exhaust valve actuator that would not function, I dissected it for evaluation. I tend to do this kind of thing when I get the chance, just for personal education....and sometimes I can fix whatever I am taking apart.
Unfortunately, the internal base is plastic welded so can't be easily reinstalled, therefore no way to repair.

Common faults with other brand actuators involve stripped gears or shorted electricals (water entry usually).

Found nothing like that here, but the potentiometer sensor is just a carbon wiper and that appears to be the component the ECU was having problems with. Can't see anything with my magnifying glass, but I bet there is some damage there from being stuck in one position for an extended period (cables were rusted and stuck tight).
I found it interesting that the wiring to the harness connector is molded into the casing...pretty sure that can't be the source of the problem.
DC bi-directional motor gets a 12v signal from the ECU to open/close the valve. Sensor gets a 5v reference voltage from the ECU to the center ring with the outer ring being ground and signal back to ECU.

Not much that can fail, and well sealed against water entry. Most exhaust valve problems and fault codes are likely caused by the cables (at least initially, like this one).
Anyway, thought I would share the photos for those members who might be curious about what's inside that box.
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post #2 of 6 (permalink) Old 07-02-2019, 11:52 AM
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Such a cheap little DC motor...the stuck cables probably killed the motor, they are not very robust.

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post #3 of 6 (permalink) Old 07-02-2019, 02:17 PM
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I read the title of this thread and instantly knew who posted it
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post #4 of 6 (permalink) Old 07-02-2019, 02:33 PM
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When I had mine replaced a couple of years back they said the main fault is the plastic gears get stripped which is usually a result of the cable/valve sticking or getting stuck. The motor trying like the little engine that could and the weak point gives way. They told me to keep the cable and any external valve pieces parts well oiled and it should be good. I'm not sure they are right but so far so good.
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post #5 of 6 (permalink) Old 07-02-2019, 02:50 PM Thread Starter
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Quote:
Originally Posted by falcn View Post
Such a cheap little DC motor...the stuck cables probably killed the motor, they are not very robust.
Nope, the little motor is just fine.... Looks just like the motor in all the other brand's actuators I've dissected. Surprisingly strong little slot car motors.

Quote:
Originally Posted by fingertight View Post
When I had mine replaced a couple of years back they said the main fault is the plastic gears get stripped which is usually a result of the cable/valve sticking or getting stuck. The motor trying like the little engine that could and the weak point gives way. They told me to keep the cable and any external valve pieces parts well oiled and it should be good. I'm not sure they are right but so far so good.
That is what I was used to seeing on the other brand's actuators. Also caused by mechanics loosening the pulley screw without holding the pulley, but mostly ham-fisted cable adjustments too tight in one direction or another.

But not so in this one. Applying 6 volts to the motor would open and close the valve just fine, but when the ECU was connected it would start to move and immediately stop and throw the fault code. I think it couldn't tell where the valve was (sensor reading) so it stopped.

My sensor ohmmeter readings on this one were kind of erratic compared to the replacement.

At any rate, yes....periodic cable maintenance and correct adjustment are a good idea. Actually, adjustment should be a rare occasion, but cable lube should be routine as they are not sealed.

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post #6 of 6 (permalink) Old 07-10-2019, 02:57 PM
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Quote:
Originally Posted by esq'z me View Post
Nope, the little motor is just fine.... Looks just like the motor in all the other brand's actuators I've dissected. Surprisingly strong little slot car motors.



That is what I was used to seeing on the other brand's actuators. Also caused by mechanics loosening the pulley screw without holding the pulley, but mostly ham-fisted cable adjustments too tight in one direction or another.

But not so in this one. Applying 6 volts to the motor would open and close the valve just fine, but when the ECU was connected it would start to move and immediately stop and throw the fault code. I think it couldn't tell where the valve was (sensor reading) so it stopped.

My sensor ohmmeter readings on this one were kind of erratic compared to the replacement.

At any rate, yes....periodic cable maintenance and correct adjustment are a good idea. Actually, adjustment should be a rare occasion, but cable lube should be routine as they are not sealed.
Encoder issue then.

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