Vis motor

[genpk]

Was doing a repair on a vis motor and pulled it to bits and found the motor seemed to work one way but not the other.
Pulled it out and tested it and it worked fine each way ?
Replaced the diode which was blown but once the motor is back on the circuit board it goes back to only working one way and the diode heats up.
Tested both micro switches , seem fine, only thing left is the relay ??
Any ideas ?

[Reebs]

Stocktake is the guru of the VIS, hopefully he'll be along to comment soon. In the meantime I've moved your thread into the technical help section

[SD1too]

Originally Posted by genpk

... and the diode heats up.

Are you sure that you've connected the diode the correct way around? The cathode should be connected to the +12v supply.



Simon

[stocktake]

If you are testing the motor by removing the the pcb from the casing and simply connecting to a 12v supply and neg then the motor does give the impression of only running one way . I am assuming you have the wiring harness to hand to see which color wire goes to which pin as they are different.

You connect 12v to blue and yellow (BY) and neg to black( B) this causes the motor to run. Pressing one of the microswitches then does nothing when depressed and pressing the other one causes the motor to stop Hence the appearance of the motor only running one way.

To show the motor running both ways on a balance Vis you need to connect a neg to the black and grey (BG) whilst the other two connections (BY & B ) are still made. On a power vis it is orange and yellow (OY) whenever you connect / disconnect the BG or OY the motor will reverse.

The diode IIRC is simply there to protect the ECU. Your vis motor will actually run without it fitted but I would not recommend it, seem to remember the Diode is a 1N 4007 from memory but I am not at home.

[genpk]

Yep, it is a in4007, pretty hefty diode for such a unit, pretty sure I put the new one in it as per circuit .i do a fair bit of electrical tech work so do understand electronics.
Whatever it is,it's almost like the motor is overloaded one way and that appears to have blown the diode , one way sort of just turns over for a few seconds but heats up the diode and the trips out my transformers overload switch.
Remove the motor from the board and it runs freely both ways.
Not much on the board to go wrong, only a relay and two micro switches??

[JerseySteve]

Had to take a deep breath before asking what is probably a very stupid question but what is a VIS motor? I have seen it mentioned many times but never worked out what it actually is

[SD1too]

Originally Posted by stocktake

The diode IIRC is simply there to protect the ECU from a short.

Hi Dave,

I thought it's purpose was to suppress the back emf when the ECU removes the earth to the relay coil. I'm sure that I've seen this in similar relay circuits. The supply to the coil is fused anyway isn't it which would provide short circuit protection.

Originally Posted by genpk

... I do a fair bit of electrical tech work so do understand electronics.
Whatever it is, it's almost like the motor is overloaded one way and that appears to have blown the diode ...

The diode isn't in the motor circuit Peter so I don't see how that can be possible.

... sort of just turns over for a few seconds but heats up the diode and the trips out my transformers overload switch.

I was suggesting Peter that if you accidentally reversed the polarity of the diode, it will conduct in parallel with the relay coil. Since that will provide a very low resistance a large current will flow through the diode, hence the heating effect you've observed. There may also be insufficient voltage drop across the coil to energise the relay, hence the erratic operation of your motor. Just a thought. What do you think?

Remove the motor from the board and it runs freely both ways.
Not much on the board to go wrong, only a relay and two micro switches??

Indeed. Have you checked for continuity in all the PCB tracks? Are any of them high resistance?

Simon

[genpk]

All agreed, your assessment re the diodes purpose re preventing feedback to the relay coils is correct, this type of setup is used a lot in audio circuits when switching channels to prevent the relay getting confused with random current in circuits.
When I get time today go back have another look at it.
As a matter of interest, found a great way of separating the top of the vis without breaking the small tabs, heat gun each tab for a short time, bend them slightly out of the way. Heat the plug pins up with a soldering iron and off it comes !!

Re the vis motors question - the Kv6 engines have two small electronic motors which control a number of flaps inside the intake manifold to optimise the engines power