3a single speed wiper motor

[dpb]

Hello

Moving on to the next problem, the wipers aren't working. As usual, the wire at the fuse was disconnected,  making me think there was some problem or other anyway.

Various tests,   voltage at wiper terminal correct when ignition switched on. Earth good.  Can move the wipers easily by hand when they are disconnected from the motor.

Battery good.  Switch on motor- with or without the wipers connected, get a large(?) current flow showing on the ammeter. The motor does not move a fraction,  as if it has some short. 

Had it apart, checked brushes and connections,  all seem good. 

I am thinking I need a new motor. They seem expensive.  Any suggested suppliers?

 

Regards

Dave

====

 

[RogerH]

Hi Dave,

did the armature move freely when turned by finger.

Did the brushes look good and sit firm.

The replacement wipers are too rich and still work badly (IMHO).

Have you considered the TR6 14W motor. It looks different but should fit. It is two speed but you only need one of them.

As single speed I think it only needs a simple change over  switch.

 

Roger

[dpb]

Hi Roger,

 

The armature moves when twirled by two fingers with the wipers disconnected,it didnt seem particularly loose though. I did wondered if it was bring fouled by the casing. Should it spin easily do you think?

The brushes look almost new. I clamped them in a bit.

 

Cheers

Dave 

[Lebro]

Check your connections.  in case you did not know (sorry if you did) the wiper motor has 12V from the ignition switch (via a fuse) on it permanantly, & the wiper switch supplies the earth connection. If a previous owner has wired the switch to provide 12V then that could be the reason you get lots of current, as the motor self park mechanism may be shorting it out.

Bob

Edited March 18 by Lebro

[dpb]

Hi Bob,

 

Yep i did know, and the wires seem right,  but i will check again.

 

Dave.

[dpb]

A check shows they are wired correctly. Earth continuity from the terminal when the wiper switch is activated, and the self park wire is removed.

Struggling a bit.   How do you remove the main gear cog?  Just want to make sure that is not jamming up somehow, and that the armature will spin by hand once the cog is removed.

Dave

====

 

 

[RogerH]

Hi Dave,

 take the top hat cover off the motor. The rack can then be disconnected. Then the gear wheel will simply pull out.

 

Roger

[RobH]

I take it this is a single-speed DR3 motor.  The high current is probably due to the motor being 'stalled' - as it runs it develops a back-emf which reduces the current but without that there is only the DC resistance of the armature winding.  

If not mechanically stuck, it could be that the field winding is disconnected in some way.  The armature will still pull a high current but the motor will not rotate.  You could check that by lifting one of the brushes - the high current should drop but there should still be a small current taken by the field. If there is no current the field is open circuit

 

[dpb]

15 minutes ago, RogerH said:

Hi Dave,

 take the top hat cover off the motor. The rack can then be disconnected. Then the gear wheel will simply pull out.

 

Roger

HI Roger

 

the cover is off, rack disconnected,   but the cog seems to be held in, possibly from below.   Won't pull out, but will spin freely once the motor is removed. So I guess there is not much wrong with that.   Put the motor back though,  and it is impossible to move the cog. 

Dave.

[RobH]

1 minute ago, dpb said:

Put the motor back though,  and it is impossible to move the cog. 

That's because it is a worm drive. You can't drive them backwards. 

[dpb]

ok,   so it seems i am left with either a dodgy motor (i'll have a go at the lifting the brush theory, Bob, once my enthusiasm has returned). or a mechanical problem.

Would still like to remove the cog to ensure i can spin the armature in situ, to make sure it is not mechanically stuck. 

 

Dave

====

 

Edited March 18 by dpb

[RogerH]

Hi Dave

sorry, there is a circlip underneath. You need to remove the motor.

 

Roger

[BlueTR3A-5EKT]

Remove the motor from the mounting bracket, remove the drive rack.   Turn the motor over and remove the C clip holding the driven gear into the gearbox housing.   Lift out the gear.   Try to rotate the worm drive of the armature end with your fingers.   Not easy but it should rotate.    Apply power to the two terminals, plus have the earth connected if you want.   The motor should work.    If not loosen 1/2 turn each the slotted screws on the brush end cover.    Re apply power.  Still no go?

Take the cover off that is over the brushes by undoing the two slotted screws completely .   Smell the inside of the motor.   If is smells burnt or ‘hot’ you have cooked either the fields or the armature.  That does not mean they are scrap, but the insulation may be compromised.

This may be because the armature was mot spinning freely in the casing after it was assembled - a common problem 

being able to turn the armature with the brush end cover only means the gearbox end bearing is not seized.

The armature must be supported at both ends.   Try reassembly and applying power again.  You say the brushes are good.  That is meaning the black carbon bites are rubbing on the commutator there is not short circuit from the brush gear to the motor case.
 

If still not go but you continue to have the high current discharge the motor needs internal attention.

Edited March 18 by BlueTR3A-5EKT

[dpb]

HI Peter

 

thanks for the detail.  I will likely get to the testing tomorrow or Thursday,   grandson sitting today.

 

Regards

Dave

====

 

[BlueTR3A-5EKT]

6 minutes ago, dpb said:

HI Peter

 

thanks for the detail.  I will likely get to the testing tomorrow or Thursday,   grandson sitting today.

 

Regards

Dave

====

 

Just one addition to the assessment tests.   Check there is end float on the armature in the casing.  You should be able to move the armature axially by a small amount (upto 1mm or 0.040”).  This is adjusted by a screw and lock nut on some motors and by a screw only on others.   If in doubt slacken it half a turn and recheck.  If it is tight the armature will not rotate easily if at all.   I test by shaking the motor.  You can hear the armature moving and being stopped by the limit screw.

Edited March 19 by BlueTR3A-5EKT

[dpb]

Hello 

 

turns out I had some time while the nipper was sleeping. Anyway,   cog removed - it was a bit stiff in its mounting, but cleaned up and then it was moving freely. I could move the armature ok without the cog in.  Tried it all again - same high current, but no movement.  It does not smell of burning,   The end float was clear,   and the long bolts were loosened.

I can only conclude that there are no mechanical problems but just that the motor is somehow broken.

 

Dave

====

 

[dpb]

To finish this one off: -

I bought a recon unit from one of our forum mumbers for a reasonable price. After some experiments (it wasn't an exact equivalent), i used my old armature in the new casing, and my old wheelbox and all is fine.

Thanks for everyone's help.

 

Dave