wipers halt half way (sometimes)!

chrismpw

chrismpw

New Member
I had a search before posting this, but didn't spot a similar issue. Apologies if it's been done elsewhere.

The ONLY thing not working perfectly (at the moment) on my '72 P6 are the wipers. When first on they often work fine, but after several minutes at low speed, or on intermittent they halt half way across the screen.
Switching the wipers off sometimes springs them back into life and they auto park.
Sometimes to get them moving I have to switch them into high speed.
They always work perfectly in high speed mode.

I've had the wheel boxes apart for each wiper and made sure they are all properly lubricated. I suspect it's an electrical issue, or something wrong with the wiper delay unit. Possibly an issue with the brushes, in the motor.

Has anybody posted anywhere how the wiper delay units work, so I can go about trouble shooting this system?
Does anybody have any suggestions where I should start looking to fix the fault?
Is it a common fault?

Cheers and beers
C
 
I don't know if it's that common, but I have the same problem with mine (also 1972) in as much as I sometimes have to switch them to fast to get them moving, but once I've done that, they're usually fine. I don't usually have a problem with them stopping across the screen, though.

I haven't done any delving to see what it could be yet - I was thinking along the lines of dodgy contacts within the motor unit. I don't know how the delay system works at this stage, other than it utilises vacuum in some way, so don't know if that would have an impact.

I'd be interested to hear what you find.
 
Have a look at the wiper delay device. If it's not working correctly it can affect normal wiper operation. IIRC if the wiper delay device operates too quickly, ie the plunger goes straight back, in the wipers can stick mid-sweep. Worth a look.

Dave
 
Thanks, Dave
Where is this device? Is it by the motor, or are you referring to the knob by my steering wheel?
 
My Rover too has experienced this type of problem, but in my case the problem was the actual switch. I checked the motor and the delay, but doing so made no difference. It was only when I replaced the switch was the problem cured!

If you can obtain a spare, undo the 4 screws securing the panel and ease forward. Disconnect the wires from the switch and attach to the spare, then test. If the problem is immediately sorted, then you have your answer. Remove the old switch and fit the replacement.

Ron.
 
I am waiting to see if it's the switch, Ron!

One other observation I made was that the halting NEVER happened without a load on - ie when I removed the wipers, they operated perfectly (apart from doing anything about cleaning the screen that is). When I put the wipers back on and used dusters under the rubber to protect my dry screen - back came the halting - always in the same place.

My current theory is that there is an issue caused between the delay switch and the parking system. Perhaps the wipers aren't getting far enough over for the power hand over.

At the weekend, then I stripped the entire motor assembly and replaced 40 year old grease, which had started to turn into wax. This waxy grease COULD have been impeding the movement of the parking switch plunger, revealed below (and operated by a cam on) the big cog inside. I cleaned all the electrical contacts I could find, and stripped the vacuum delay unit - being careful to de-oil my fingers first to stop oil attacking the rubber membrane. Inside the vacuum switch are some contacts that were my chief cultprits so these were cleaned up too. There was some signs of water ingress here - possibly condensation over the years.

When the wipers first sweep, the action lifts a white plastic slider/follower up the top plate f the wiper motor assembly up towards the cab, and the follower lifts the vacuum switch plunger (photoed above). First I cleaned the follower up, because its action looked sticky - but to no avail. ( I think there should have been a spring on the follower too - for its return path - but mine relies on gravity). While being pushed up, the air from the vacuum switch escapes from a valve on the top of the vacuum unit. Having been evacuated, the diaphragm and plunger stay where they are put, unless air is allowed to enter (at varying rates) from the control knob on the steering wheel.

On re-assembly I had a very intermittent vacuum delay - so I had disturbed the valve at the top. I gently prized away the small rectangle of stainless steel that holds a small rubber disk in place and was surprised to see that there was nothing else to encourage the disc to stay in place. Having first cleaned the valve, I then cut a tiny piece of neoprene to fit between the metal rectangle and the rubber disk, which provides a little positive pressure to hold the rubber disk in place.

Using the dusters again, it APPEARS that the problem is fixed ... no halting now under load. So it was either the waxy grease, slowing switch operation or dodgy contacts. All I have to do now is a rain dance, to test them out properly.

Cue drought.
 
Done! They work beautifully after this work. I think the main culprit, as has been suggested, is the delay switch. So inspired was I that I also gave a good service to one of the wiper motors on my 1959 Land Rover, last weekend.

So now I know they're fixed .... can somebody turn off the rain, please?
 
I thought the delay switch simply gave a short burst of current to start the wipers then left them to finish the sweep and park as normal. I.e. it's the same as switching them on for a moment then off again. So I don't see how that could make any difference during mid sweep.
So an electrical issue seems more likely to me. I.e. just a bad connection somewhere that you've managed to cure while doing the above work.
 
The delay unit itself plays no part in the operation of the wipers in either slow or fast speed modes.

I wrote a thread on revitalising the wipers a while back, and is a sticky at the top of the electrics section:

https://classicroverforum.net/index.php?threads/36024/

Towards the end I wrote a section on how the electrical side of the wipers operate, and in the case of a fault with the slow and fast speeds, (during normal operation that is), the primary suspects would be the wiper switch itself, or any of the wiring contacts. The parking switch only comes in to play when the wipers have been switched off, to allow them to.... err... park.

Your initial description seems to support dirty contacts rather than the grease cleanup. It wouldn't take much of a dirty contact to give enough resistance in the circuit to stop the wipers operating properly, but I think the motor would be more likely to not start when first switched on, rather than stop after a few minutes, if it was the grease offering too much resistance to proper operation, which I believe would be unlikely anyway.
 
Willy Eckerslyke said:
I thought the delay switch simply gave a short burst of current to start the wipers then left them to finish the sweep and park as normal. I.e. it's the same as switching them on for a moment then off again. So I don't see how that could make any difference during mid sweep.
So an electrical issue seems more likely to me. I.e. just a bad connection somewhere that you've managed to cure while doing the above work.
Click to expand...

I can confirm quite categorically that if the delay operates too quickly it can stop the wipers mid-sweep ;)

Dave
 
Dave3066 said:
I can confirm quite categorically that if the delay operates too quickly it can stop the wipers mid-sweep ;)

Dave
Click to expand...
Looking at the circuit diagram, (at least for my 1972 3500S), I cannot see how that can happen, unless the parking switch also failed to operate properly. This however would, (should), have also given you an issue with the normal slow and fast speed modes, whereby the wipers would not park correctly once switched off. As I mentioned earlier, the delay governor plays no part at all in normal slow or fast speed wiper modes, (again according to the diagram for my vehicle) :confused:

Under normal conditions, the parking switch changes before the delay governor. If this happens in the opposite manner, (because the parking switch is stuck for example), then you will indeed have the wipers stopping midway. They will eventually start again, once the parking switch operates, or stay where they are if the parking switch has failed.

Beginning to doubt my thinking of how this works, I have just been out to the car and disconnected all electrical connections to the delay governor, and as expected the slow and fast speed modes still work perfectly :)

In delay mode, if the governor failed to switch from it's starting position, then you would get permanent power to the slow speed motor, and the wipers will therefore behave in the same manner as slow speed wipers. If the governor operated but subsequently failed to return to its idle state, then you would get an endless delay, once the wipers had returned to their parked position.

The change of state of the parking switch places power onto the contact of the governor, that will be switched to once the governor has changed from its idle state, thereby allowing the wipers to complete a sweep. When the wipers return to the parked state, the power will be removed from this governor contact, and the wipers will stop. They will only restart when the governor switches back to its idle state, whereby the whole process is repeated.

Which of your vehicles did you have this issue with? Do you have the circuit diagram for it, so I may see if it operates differently :)
 
codekiddie said:
Which of your vehicles did you have this issue with? Do you have the circuit diagram for it, so I may see if it operates differently :)
Click to expand...

Phil

That was also on my '72 3500S. It was bizarre, and I can only talk about what I experienced, but it did affect the operation, and slowing down the delay definitely fixed it. I should add that the delay was not "delaying" at all. The plunger came straight back out again and the wipers stopped mid-sweep. Once I fixed the delay the wipers started working normally. I didn't touch any other part of the wiper circuit.

Dave
 
One thing I forgot to mention ... was one of the motor brushes was a bit sticky and, I reckon, slightly limiting the flow of electrons resulting in a slower sweep. Clearing this up, and cleaning the commutator may have helped too. One thing I haven't touched is the wiper switch in the cab.

I have added - clean wiper motor brushes and commutator to my list of things to do to the car every 35 years.
 
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