Problem With My Fron Wipers

[gazknight]

Hi All

I have been a member for some time, but not posted any questions yet as I have always found the answers I needed using search.

 

My current problem has me stumped; and I have searched through the forums and not found any matches.

 

I have wipers that work perfectly well most of the time, but sometimes do not work at all.

 

This has happened twice now, the first time I was on my way home from work and the heavens opened; turned the switch on for the wipers and nothing happened.

I sat at the side of the road for a while scratching my head and looking for blown fuses or loose wires etc. but could not find anything and so set off the 9 miles home at a snails pace.

Next day, got in the car and the wipers worked perfectly and have done ever since.

 

Haven't thought about this since then, until driving home from the coast yesterday and the same thing happened again. This time I had to drive 80 miles in the rain; and to add to the frustration, the blooming things had been working in the morning on the way to the coast! Again, next day they are working pefectly.

 

I have searched through the forum and found a number of threads suggesting that the mechanisms seaze up, but I dont seam to have the symptoms of this happeneing; there is no juddering of the wipers, the shafts dont heat up when in use, and when they are working they work perfectly.

 

Other symptoms; when the wipers are not working, the screen wash and rear wipers still operate as normal.

 

I find this very difficult to diagnose because the problem is no longer there to find; so I am hoping someone out there has some ideas for me to start looking into. I suspect that there is an electrical fault somewhere, but I need some advice about the system, I have no workshop manual as I dont think one is available. Please correct me if I am wrong I have a V reg 2.8 V6 ghia.

 

Gaz

[gazknight]

Hello All,

Seems I have got everyone stumped with this one;

Further symptoms have emerged: I have used the wipers everyday this week with no problems both morning and evening.

Except Friday, on the way home it was not raining but tried the wipers just to check - nothing and they have not worked since.

 

I have had all the fuses out and checked them with a meter.

I have removed the wiper motor assembly and the wipers move freely.

I have had the switch off the steering column and checked it with a meter.

I have checked that there is power to the motor assembly and that switching the motors on changes the voltages on the input to the motor PCB.

I have put 12V directly to the motor and it turns.

 

My diagnosis is that there is a problem with the PCB that controls the motor.

Does anyone agree and can anyone advise me on how to check this or about replacing it.

 

Thanks,

Gaz

[veedyf]

id just replace it (it is the wiper ecu your on about aint it ) most common problem as it can get damp easyly... i have sold 2 recently ....for 30-40 quid each on ebay

[Mirez]

I would tend to agree, there is a load measuring circuit within that PCB that will shut off the wipers if the current is too high. If you have no obstructions, the wipers move freely and they are the right size (ie not coliding with each other) then I would assume the PCB is failing. You could take it apart and examine for dry joints as I'm sure its going to be something along those lines.

[gazknight]

Hi Thanks,

I have the PCB off now and it deffinately looks like water damage.

Cant see any dry joints, the PCB is coated in a prtective barrier - is this normal?

Gaz

[seatkid]

Yes, I think the PCB is conformally coated with some kind of lacquer. This is usual practice where water/moisture is expected.

 

IIRC the failure of this module is due to

 

1. A stalled motor leading to overheating of one of the power mosfets, which fails either sort circuit (wipers permanently on) or open circuit (wipers not working)

once blown this is a permanent fault. An electonic engineer may be able to replace the faulty mosfet. Check the fuse in the fusebox is of the correct rating as this should blow first.

 

2. Water getting under the lacquer coat and corrosion/moisture leading to the module intermittently not working or permanently stuck on. In this case, drying out the module and cleaning up the corrosion using solvent based cleaner, may solve the problem. After you get it working, relacquer the board to prevent reoccurence. There is a chance that the corrosion/moisture leads to a condition where 2 mosfets are on at once and one of them blows (see 1)

 

New modules are horrendously expensive.

Edited August 19, 2008 by seatkid

[gazknight]

Update on progress:

 

The module is definately at fault, I have borrowed the same unit from a friends car and that works as expected.

 

My best efforts with the conformal coating on the PCB have just made a mess; one on the surface mount resistors came off as I was doing this.

With the resistor remounted and the board dried out with a heat gun, the unit still refuses to work.

 

I think I will have to bite the bullet and get a replacement.

 

Gaz