Crystal Cranks

I have had a similar problem a couple of years ago,

https://rennlist.com/forums/964-foru...n-storage.html

Looks like its something that happens after reconnecting the battery after winter storage, this time the down motor is activating on it's own randomly and does not shut off when the micro switch (tested and working) is activated when fully retracted.
When operated by the center console switch (tested working) up is fine but when down is activated it will not turn off.
The motor will only turn off when power is removed from the controller unit.
I have disconnected the drive gear to stop it from getting chewed.

I'm not interested in a replacement as a lot of them will have problems if they have not been refurbished, I want to repair this one.

From reading up on this it looks like it might be a bad transistor or maybe a bad relay.

I'm happy to do a bit of soldering if I'm shown what needs to be done.
Can any of the experts on here help me?
(1990 C2 older two units under seat)

Crystal Cranks

Can't see anything obvious.

klokwerk

Hey there. Sorry you're having trouble.

I worked through issues with my spoiler last year. My car is an 89MY and also has the controller, backup, and relay like yours.
First, there's just one motor. It gets run fwd or reverse to raise or lower the spoiler.
At the top or bottom of travel, the spoiler contacts the micri-switches to tell the controller to turn off the motor and set the direction for when the motor is turned on again.

T​​​he Relay allows the controller to send higher voltage to the motor using a smaller signal from the contoller.

If the motor runs it's because the contoller told it to and if it hits the switch but doesn't stop then either the signal isn't getting to the controller or the controller is busted.

in my case the motor needed replacing. Old one was rusted and seized and the controller was broken.

Now it works like a champ.

Good luck troubleshooting your isse. If you don't have the schematic for this system you should dig it up.

ToreB

First, check end travel switches in the spoiler mechanism. If OK, change the two BC337 relay driver transistors on the top of your PCB picture.
Cheers,
Tore

Crystal Cranks

Thanks Tore, I was hoping you might reply, yes all Limit switches are working, just ordered some bc337's will let you know how I get on.

mojorizing

It sounds like you have a high resistance to ground on two of the wires going from the limit switches back towards the module. Each limit switch has one side going to ground with the other side going to the base of the respective transistor that drives the its relay.

How did you electrically test the limits?

To test the ground connection separate the limit switch plug connector (on the spoiler) and you’ll see two pair of connectors. Each side of the connector pair should go to the car’s ground with no resistance, the other side of the pair should be high maybe 500K. Note: This is testing the circuit going to the module, not to the limit switch side. The ground (pin 5) and the ground from the limit switches are not the same wire.

I have the schematic of the module generated myself – pm me for it.

Crystal Cranks

Thanks,
I will check the grounds on the limit switches on the control unit side of the plug. I had just tested the switches were open and closed circuit at this plug when manually activated.
Where is the ground on the chassis for these wires?

Do you think this could make the control unit send power to the motor randomly?
And also not stop power when the centre console switch is used, the spoiler should stop in any position when the centre console switch is released, in this situation the limit switches should not have any influence on the operation.
Thanks

mojorizing

The workshop manual says that the ground point is at the cross member under seat right. A floating ground could make the module act erratically.

Crystal Cranks

Thanks gents,
Replacing the two transistors seams to have done the trick, hopefully for good I don't fancy burning out the motor and drive gear $$$$$$$$$.