Is this one of / the answer to the throttle actuator problem - BMW M5 Forum and M6 Forums
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post #1 of 14 Old 22nd June 2016, 01:03 AM Thread Starter
gmak
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Is this one of / the answer to the throttle actuator problem

1. TA-1 with the circuit board off. Returns to starting point rather rapidly, no?
2. I've put small wire probes into the two connections on the circuit board. I then attach the alligator clips to the big flat connectors (to the motor) in the TA-1
3. I do the lever / gear thing AND LOOK HOW SLOW THE GEARS RETURN TO STARTING POINT.

All I can think of is that the capacitor in the circuit board cover has a charge and that it is affecting or activating the motor somehow - with the results that cause the errors on start up test due to the slow return.

[YOUTUBE]https://www.youtube.com/watch?v=Ayekf_xSDCY[/YOUTUBE]

Now, can someone tell me how to pop the motor out? Why, if it's getting power, does the motor slow down the return? Is this more of a circuit board thing?

Will anyone answer this? Can anyone replicate this?

Last edited by gmak; 22nd June 2016 at 01:05 AM.
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post #2 of 14 Old 22nd June 2016, 01:20 AM Thread Starter
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Hmmm. A bunch of views and NO COMMENTS, no ideas, nothing? Don't you think that this is new and evolutionary information that could lead to an inexpensive solution to the Throttle actuator problem - especially if replacing gears doesn't work?

Even if this is the stupidest thing you've ever seen and I'm wrong wrong wrong with the idea that this is the cause of the problems (is this normal operating behaviour? Is this something that changing the gears will fix? (spoiler: no) - TELL ME.

C'mon give me an opinion.

Last edited by gmak; 22nd June 2016 at 01:22 AM.
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post #3 of 14 Old 22nd June 2016, 01:29 AM
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The reason for the TA to return to rest position slowly when connected to the (powered) PC board is that the H-bridge implements a short through the back gate diodes of the MOSFET. When the motor is shorted the back EMF generated in the motor as result of the spring driving it, causes a current to flow (which is shorted out). Rotational potential (spring) energy is converted to heat in the motor windings. Moreover it creates a magnetic field which slows the motor down. That is the reason for the slow return. Expected behavior. If you do not believe me, short the motor out on its terminals and you will see the same behavior.

Last edited by rt7085; 22nd June 2016 at 04:16 AM.
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post #4 of 14 Old 22nd June 2016, 01:36 AM Thread Starter
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Quote:
Originally Posted by rt7085 View Post
The reason for the TA to return to rest position slowly when connected to the PC board is that the H-bridge implements a short through the back gate diodes of the MOSFET. When the motor is shorted the back EMF generated in the motor as result of the spring driving it, causes a current to flow (which is shorted out). Rotational potential (spring) energy is converted to heat in the motor windings. Moreover it creates a magnetic field which slows the motor down. That is the reason for the slow return. Expected behavior. If you do not believe me, short the motor out on its terminals and you will see the same behavior.
I believe you. I tried it on TA-1 and not only is it slow return, but it is very hard to move the gear. SO what you're saying is that I have a short on that circuit board? Because I get the the throttles just springing back on TA-2 and it does the flickering when ISTA tests it.

How come my TA-1 works one minute and not the next? If this is indicative behaviour when the circuit is complete than how does the TA ever pass the pre-start test?

Last edited by gmak; 22nd June 2016 at 01:37 AM.
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post #5 of 14 Old 22nd June 2016, 01:54 AM
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Is this one of / the answer to the throttle actuator problem

No, MOSFETs block current only on one direction. There is an unintentional diode across them (internally) that causes the 'short'.

The intermittence is a result of the internals of the TA not passing some kind of self test. If it fails it throws an error status in the CAN response and turns into a vegetable until the next power cycle.

Last edited by rt7085; 22nd June 2016 at 04:19 AM.
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post #6 of 14 Old 22nd June 2016, 01:57 AM Thread Starter
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You're probably right, but on my TA-1, when I short across the motor (no circuit board involved), it blocks/ slows down (huge resistance) in both directions.
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post #7 of 14 Old 22nd June 2016, 02:00 AM
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If you want to remove the motor in the TA just remove the two screws that hold it in and put it face down and hit the back with a dead blow hammer or similar several times and it will fall right out.
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post #8 of 14 Old 22nd June 2016, 02:08 AM Thread Starter
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Quote:
Originally Posted by mattcon View Post
If you want to remove the motor in the TA just remove the two screws that hold it in and put it face down and hit the back with a dead blow hammer or similar several times and it will fall right out.
Thank you. I'll give it a try.
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post #9 of 14 Old 22nd June 2016, 02:13 AM
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You want the motor to resist in powered (but closed) mode. The butterflies have to stay closed out of fail safe considerations. If you open the butterflies you would accelerate.

Last edited by rt7085; 22nd June 2016 at 03:57 AM.
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post #10 of 14 Old 22nd June 2016, 02:46 AM Thread Starter
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Still. I have 2 TAs behaving differently. What you are saying is that the TA-2 which has no resistance is not working properly. Don't the throttle valves get held in position by their own springs? They're not going to pop open unless the motor is activated. And they have to return to closed fast - or else you would not have proper control when the foot comes off the pedal.

Maybe you should explain everything to me in baby steps, because clearly I am confused and don't understand.

TA-1 which is out of the car, shows no resistance when the circuit board is off. When the circuit board is on, it shows only resistance to returning to rest (throttles closed). When I short across the motor terminals, with no circuit board, it has great resistance in both directions. Resistance here being of the mechanical kind, not electrical.

TA-2 which is in the car - when I open all the throttles manually, they spring back closed instantly when I release the lever. (Unlike TA-1, which when in the car would see the throttles on that bank close slowly - twice as slow - when opened manually like I ddid for TA-2. Different behaviour from the two throttles in a shut off cold car.

In any case, I've ordered a new one (VDO) from Spareto.com (european) for quite an attractive price given the cost over here in NorthAm.

Last edited by gmak; 22nd June 2016 at 02:50 AM.
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