Auto 2.1 Bosch Starter Motor Solenoid Test

[937carrera]

Good reading and thanks. Yes lve read brushes act as earth. As does small end cap held by two screws.
Also all outer body connections must be free of corrosion too. In this case, front part, centre case and end case with small cap.

Those screws are screwed into the body on the solenoid, no ?.......... so body should be earth

Lastly the wire from solenoid to starter should be isolated by a rubber grommet in the casing? The one on this starter is a bit manky.

Manky wires are the common fault mode for slow starters as they cannot carry the current

Manky insulation = current can flow to the body of the starter instead of to the motor ? If so much sparkiness can ensue, as you are effectively creating a battery short ?

I think this is your problem

[bigherb]

Stu, to test the solenoid you need to have a 12V cable connected to the main solenoid battery terminal and then connect 12v to the solenoid trigger terminal obviously the body has to be earthed. These motors work by the trigger terminal turning the motor slowly while it engages with the flywheel before the solenoid contacts close and power the starter motor. If you don't have a 12v feed to the main solenoid terminal you will just be testing the throw in part of the solenoid but it will rapidly overheat the solenoid windings.

This is how the pull in works as you can see it needs 30+ amps to pull the starter in. That's why it is a good idea to fit a starter relay.
https://www.youtube.com/watch?v=5z4By7XR5sI" onclick="window.open(this.href);return false;

[maxstu]

Thanks to both above l now have two spare working auto starter motors.
On both l changed the wire from solenoid to starter. Cleaned everything with clutch cleaner, both have good carbon brushes, and used on the one in discussion above gasket sealant to isolate newly made cable from casing. That did the trick.
For the new cable I used a bit of 16amp camping cable. Stripped back all the sheath to bare cable. Then put three same size pieces in a vice and made this by winding the three strands in a plaid? Plat? Whatever its called
Soldered to solenoid and starter contact plates. Bolted up solenoid plate and all good.
However l dont think this is beefy enough for a permanent repair.



Running up both starters gave me a chance to compare performance.

One is very quick and spins up well, yet has a slight rattle near nose cone...bearing?
The other fired up then stopped after a second. Then started sparking as before. Bummer. So l gave the shaft a quick turn by hand. Added voltage and its been fine so far.
Who knows? Im going to test both once a week for a month then if all good put one up for sale.
Thanks to all
Regards
Stuart

[937carrera]

That's great news, glad I could help along the way.