Hi Everyone, I'm new here so please forgive a topic which may have been done to death.

 

My background is field service engineering, so I am used to finding obscure problems and repairing them without the benefit of all the spare parts!

 

The rear screen wiper on our Mk2 Scout became intermittent and then stopped all together a while back, and I think I've round the solution!

 

In this case though its not obscure at all - it's a very common issue with any system where a printed circuit has solid connections to the outside world, especially where these connections are the mechanical anchors for the board.

 

The rear screen wiper drive assembly contains a small PCB, with connections to a 4 pin connector (earth, +12, and two control pins). Internally, here are two connections to the motor which are made via soldered pins within the assembly - and that's the problem. In my Skoda Scout, the soldered joints on these connections were "dry" where either due to poor soldering at manufacture or vibration induced fatigue failure of the solder, the joint looses integrity.

 

It's simple to fix if you're handy with a small soldering iron - and a breeze if you have prior experience as a hobbyist in electronics.

 

Getting to the assembly inside the rear door is the hardest part - popping the cover off - but I'll leave that for you to look up  how to do this on this site and or any number of others!

 

I removed the whole drive assembly - unplug the cable, take off wiper arm, and remove three 10mm head bolts, but if you're a contortionist you might be able to do the job without assembly removal.

 

You will see a small rectangular cover (about 35mm X 25mm) on the front (/back?!) face of the assembly near the connector - use a fingernail to get it off, a screwdriver is not required.

 

You'll see the PCB as in the attached picture (sorry about focus but its good enough!). I have arrow-ed the two offending connections. If you use a decent magnifying glass youll see that the solder around one or both the pins looks like its cracked and crumbly - that's classic "dry joint" appearance!

 

Ideally, remove the existing solder (with solder wick or a "solder sucker") and then carefully re-solder those two joints. If you can't remove the existing solder, though, just apply a minimum amount of quality resin-cored (electronics) solder and apply enough heat to allow the solder to flow around the pins. Inspect the joins to make sure the surface is nice and shiny with no cracks. Incidentally, the joints on that board look too shiny to be ROHS compliant non-Lead solder, so you might find old school lead-tin solder if you have any, will be easier.

 

Clip the cover back on, reconnect the cable and give it a test - in my car (2l Diesel Scout) the engine has to be running for the rear wiper to work (that had me tricked for a while! (-: )

 

Respond with any comments or questions! As a newbie, I welcome constructive input!

 

 

 

 

Edited 28 July, 20205 yr by john999boy
Updated title

A very informative first post. 
Welcome to Briskoda.

 

Thanks for sharing.

 

Too complex a design.

 

It used to be water ingress past the wiper shaft bush when the grease no longer sealed and the gear mechanism would rust to a standstill.

Thanks for the observation about water ingress. Micmac. I had seen mention of that problem on the site.

 

Maybe they fixed that or else in Australia the seal is not as stressed (not much ice where this car lives!). Certainly no sign of water in the gearbox (I looked!). IMHO, the mechanism seemed very nicely engineered.

 

Given that there are many stories of such intermittent behaviour followed by total failure, I’m sure the problem is as I described. The repetition production of such things means the problem would be duplicated and widespread. 

Lead free solder joins, car vibrations and Ozzy temperatures=failure.

Does get a bit warm here, but it does elsewhere.

 

Do ROHS systems exhibit lower numbers of dry joints? That’s an interesting point!

I think you mean non RoHS compliant lead/tin solder.

 

Lead/tin solder is mostly only permitted in aerospace/specialist industry as lead free is known to cause dry/brittle joins.

 

Electronics fail worldwide but more so with extremes of temperature, often not due to component failure but the crap solder.

 

Resolder adding flux for a factory repair or do it properly with lead/tin solder.

Thanks for pointing that out MicMac,

 

On reading your earlier post more carefully, I see I misunderstood it first time round, and that in fact you pointed the finger at non-lead solder. My gut feel was that that would be the case, totally agree with you.

 

Watching molten non-lead solder cool, you see the surface go from shiny liquid to frosted solid - nasty brittle-looking stuff indeed! Certainly not eutectic behaviour. I don’t think the original solder was ROHS, the solder was shiny, but cracked around the pins.

 

I’m sure the joints failed due to mechanical vibration. Being bolted to  the back door which is routinely slammed shut would probably be the source of the vibration.

Welcome. Thanks for this.

 

As you may know the estate version is not quite as susceptible to failure as the hatch version due to the routing of washer pipework through the shaft on the hatch. Which is usually a recipe for failure.

 

Nevertheless, as with yours, my estate version became intermittent then non functional after about 8 years. I pulled it out cleaned and lubed gears and used contact cleaner on the commutator and brushes. Also made sure there was brush length left and they were holding the brushes against the commutator. Reassembled, it worked slightly better but still intermittent then shortly after same again. 

 

In the end I got fed up and bought a aftermarket magenti morrelli motor which, while not genuine price was still £40 or £50.

 

I've still got the original genuine in the shed I may go and have a look at those contacts! . Thanks for the post.

 

 

Thanks MicMac, if you do check your old one and find my diagnosis correct, it might be helpful to others who battle with this to hear corroboration.

 

Cheers,

 

Robmel

Ooppps sorry, TheClient!

@Robmel

 

That's okay we'll make allowances for all the blood going to your head!

 

You being upside down 'n' all 😄

Hello,

 

I had the same issue on Skoda Yeti, so I hope it helps someone.

Bad I didn't find this post earlier. It would save me hours as I thought issue was with plug connectors behind left boot trim cover panel.

 

The problem was the same as described here, bad joints on PCB powering the motor.

 

Cheers

 

 

Glad it was helpful!

 

Almost certainly the problem will be widespread through the whole VW manufactured range.

 

Question to moderator:

 

Can this solution be more widely associated with other vehicle models?

Hello,

 

I had the same issue on Skoda Roomster, rear motor 5j7 955 711.

Cheers.

I had the same symptoms and it was the brushes sticking in the brush holders. The pressure from the brush springs reduces as the brushes move down the holders with brush wear. It gets a to point where the brush spring cannot overcome the stickiness of the brushes in the holders.

Clean everything and scrape the sides of the brushes. Check they can move freely.

How bad a job is it to remove the inner boot cover get to the motor? I'm going to guess a fair amount of fiddling?

2 hours ago, sandspider said:

How bad a job is it to remove the inner boot cover get to the motor? I'm going to guess a fair amount of fiddling?

 

From what I remember on the estate, it is just a matter of removing the rubber pull-down strap then unclipping the trim all the way round. The hard part is clipping it back into place. 

Perhaps others on here can provide a guide or a video?

 

An update...

 

We're selling the car (it cannot tow the small caravan we have bought because of weight restriction). Murphy's Law has caused the problem to return ... And it was caused by the same soldered joint failure. Easy and effective fix. I considered adding some hot melt glue to support the board, but since I'm selling to a friend, I'll let him do it next time!

Well, I've finally got around to looking at this. Got the boot liner off, with only a clip or two broken, but the solder on those two pins looks fine. I went to unbolt the wiper arm to pull the motor off, but it's jammed / rusted solid - if i try any harder I'm pretty sure I'll break the motor mounts or the rear window! Left it soaking in penetrating oil but fear it may be a garage job - or I'll just live without a rear wiper.

54 minutes ago, sandspider said:

Well, I've finally got around to looking at this. Got the boot liner off, with only a clip or two broken, but the solder on those two pins looks fine. I went to unbolt the wiper arm to pull the motor off, but it's jammed / rusted solid - if i try any harder I'm pretty sure I'll break the motor mounts or the rear window! Left it soaking in penetrating oil but fear it may be a garage job - or I'll just live without a rear wiper.

 

What about using a windscreen wiper removal tool? That's what I used on the front wipers on my car.

I don't have one. Also I dismantled everything else I could, cleaned it out, removed corrosion, lubed it etc. and it still doesn't work! Darn.

I got mine from Machine Mart, only £5.99 but they don't appear to have it at that price anymore.

 

Ebay or Amazon do them cheap.

Just to say, I seem to have finally fixed this! And it was soldering the pins as mentioned long ago by Rob.

Thanks Rob! 😁

No worries! We ended up with a Subaru Outback which seems a fine car. I really miss the scout though! That sweet little Diesel was a joy! Pity Dieselgate sealed the fate of European manufactured Diesel cars ... Curse you VW!