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Marty
Marty, European Car Expert
Category: UK Car
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Experience:  ASE & Bosch Certified Master Tech. Over 30 years experience.
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190e: windshield wipers come on when headlights switched o

Customer Question

windshield wipers come on when headlights switched on
Submitted: 1 year ago.
Category: UK Car
Expert:  Marty replied 1 year ago.
Hi, and welcome. My name is Marty. Sorry for the wait. If the only problem that you are having now is with the intermittent function the problem will most likely be a faulty N10 combination relay. The relay controls the intermittent function for the wipers. The relay is located in the very back of the fuse box. I've marked the location in the diagram below. I would substitute a known good N10 relay and see if that solves the problem. This problem can also be caused by a bad park switch in the wiper motor but the relay is the more common problem for this symptom. I'm assuming that when you turn the wipers on intermittent that they just wipe continuously. If nothing at all happens on intermittent but the wipers work on low and high the problem could be a bad wiper switch.

Let me know if you have any questions.

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Customer: replied 1 year ago.

no. do not assume " turn the wipers on intermittent that they just wipe continuously"


 


you missed the sequence:


 


-i live in Denmark which requires headlights on night or day


 


-suddenly one day two hours from home, when i turned on the headlights the windshield-wiper started (on continuous low speed)...lights OFF-wiper OFF.....move wiper switch to any position and the wipers just stayed on continuous-low, push for wash and the went to continuous-high for a while.


 


-i pulled fuses until i found the one which killed the wiper but left the headlights on, and continued my trip


 


-friend, shade tree mechanic fought it (with google) off and on for days, checked all grounds and could find none bad...he pulled a 'module' (maybe he called it a 'relay' ?) from a wreck/hulk put it in and then i could have lights ON without the wiper running constantly....but, the wiper would no longer run in the intermittent setting..


 


-some days later when he had time to "fool with it" he replaced the headlight switch (from a hulk) and put back in the original 'module'/relay and everything worked as expected (had full control of all wiper functions with the headlights on or off!!


 


- went like that for _months_


 


-then, suddenly last Saturday night, turned on the lights and wiper came on continuous-low. he worked it for hours on Wednesday, rechecked grounds and finally put in the same 'module'/relay which was known to allow lights ON and wiper OFF, but again (as expected) it now has no intermittent wiper setting. i can almost live with it like that, but we have misty dripping rain here a lot and the intermittent setting is really nice to have!


 


do you think maybe put back in the original 'module'/relay and focus on the "bad wiper switch" of your answer? is that on the steering column or is it one and the same as your answer's " bad park switch in the wiper motor"?? if either might be the cause is there a way to know which?


 


*or* maybe the N10 could still be the cause...and, he replaced one with a fault, with another one with a different fault?

Expert:  Marty replied 1 year ago.
Hi, it sounds to me like the used N10 is the problem. The failure of the intermittent wipe in the N10 relay is a common fault. I would look for another used N10, preferably one that you can test to be sure it works and install it.
Customer: replied 1 year ago.

Marty, i WILL get back to you...may take a few days...


(can't 'rate' until the prescription has been tried)

Expert:  Marty replied 1 year ago.
No worries, I'll be here if you need more help with this.
Customer: replied 1 year ago.

no, you totally missed the most important part, twice:


 


**Problem: the windshield wipers come on when the head lights are turned on, and go off when the headlights are turned off**


 


the intermittent wipers not working 'problem' you have focused on and answered (twice) is _not_ the problem, it is instead intentionally put in the system to allow the car to be driveable--thesequence of actions to try to get the wipers to stay off when the headlights are turned on were:


 


1. the switch on the steering column was ruled out as the problem by unplugging all leads to the stalk (and the wipers _still_ were on/off with the headlights)


 


2. all front, rear and side lights grounds were checked, cleaned bright and set tight. (_still_ wipers on/off with lights)


 


3. headlight switch replaced and several of those easiest to get to grounds under the dash were serviced/checked...(but still wipers on/off with lights)


 


4. to make it drivable, the intermittent circuit in the N10 relay was disabled. (so your last instruction to get a new working N10 is wrong...i have a working N10, and when not disabled the wipers are on/off with the lights..


 


5. drove it like that until he had time to fool with it again and when he again enabled the N10 intermittent relay it was *fixed*, like magic with nothing else done..


 


6. then a few weeks later it started again...i downloaded and studied wiring diagrams and saw a path through the washer reservoir...so i wiggled the electrical connection on the reservoir and it was
fixed again!


 


7. until last weekend and _again_ wipers come on with lights...


 


8. mechanic rechecked grounds, ran out of time and again disabled the intermittent wiper circuit in the N10.


 


this may be hopeless....i know i have already used more of your time than you like . . . but it ain't fixed yet...



if you don't have any advice other than replace the N10 or check grounds i'll move on..


 


i may just sell it, as is..

Expert:  Marty replied 1 year ago.
Hi, sorry for the misunderstanding. I thought the headlight problem was solved and you were only dealing with the intermittent wipe problem. I have a few questions.

When the headlights are off, do the intermittent wipers work with either relay installed?

Which fuse did you remove to allow the wipers to stop and allow the headlights to remain on?

Can you remove any other fuses that will turn the wipers off when the headlights are on (even if the headlights turn off when you remove the fuse). If so, can you list the fuse numbers?
Customer: replied 1 year ago.

the #20 fuse was removed to stop the wipers and lights from being on/off with the headlight switch.


 


the other two questions you asked will require the N10 intermittent circuit to be re-enabled prior to testing..


 


my mechanic didn't have time to work/test it today..(as it *is* driveable it is not his or my highest priority--and Thursday is a religious holiday in Denmark, so it may be some days yet..)


 


additionally! he pointed out to me that my memory was faulty: in fact the lights and wiper on/off together problem was solved immediately after the headlight switch was swapped out (item #3 in my Monday, May 06, 2013 11:53 AM EST input to you) and it stayed 'fixed' for months...and then item 6 occurred, not in weeks, but months later..


 


dd

Expert:  Marty replied 1 year ago.

Hi, sorry for not replying sooner I have been away. Your mechanic needs to be able to duplicate the problem when the lights are turned on. Next he needs to remove the N10 and probe the terminals and see which terminal is getting powered by the headlight switch when this occurs. He should switch the headlights off and on to see which terminal is getting powered. Next he needs to trace that circuit back and look for a short in the wiring or in the fuse box. He also needs to probe the wiring on the wiper motor itself to see which terminal is getting powered.

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