Cause: Could be a number of things, however, the common points of failure are the headlight wash/wipe control unit and the headlight wiper motors.
How to fix: Working headlight wash/wipe systems are the exception. They’re not well understood or documented which can lead to difficulties troubleshooting. Because they’re not essential they are often not fixed and the moving parts degenerate further.
This FAQ is a troubleshooting guide, fixing generally involves replacing failed components. For me, troubleshooting was a time consuming voyage of discovery over a period of months and, based on the experience of others I have discussed it with; it may well be one for you too. However, it’s worth it in the end. If you haven’t done any electrical troubleshooting before then read the Bentley manual for general tips.
I don’t guarantee success in every circumstance – for obvious reasons I only carried on troubleshooting until I found the cause of my problem. However, I did devise tests for every part of the system – I just didn’t use them all in anger. I have, nevertheless, checked that they do work as expected.
1. Firstly rule out the simple and obvious.
Check for operator error. With the ignition on and headlights on press the button on the end of the right hand stalk on the steering column. This button operates what is known as the service wash.
The service wash squirts a short burst of undiluted screen wash from the small fluid reservoir nearest the cabin followed by a longer squirt of diluted screen wash from the larger fluid reservoir next to it together with the operation of the windscreen wipers. Then it squirts a burst of diluted screen wash on the headlights together with the operation of the headlight wipers.
The headlight wash wipe system will only work when the headlights are on. If the headlights are off then only the windscreen wash will operate. Some owners report that on their cars the headlight wash/wipe operates every third press of the button. It is worth ruling this out on your car by operating the service wash for five times, pausing for say 10 seconds between cycles. If it still doesn’t work then you have ruled out operator error and you can move on to the next step.
Check fuses. The wash wipe system is protected by the same fuse as the horns. If the horn works then the problem isn’t the fuse. If the horn doesn’t work then check the fuse. You may coincidentally have problems with both the horn and the headlight wash/wipe independently of the fuse, but it’s unlikely. If the horn works then move on to the next step.
2. Approach to troubleshooting
Having ruled out the simple and obvious, my approach is to check the common points of failure first. To be honest my actual testing was more random than this but having gone through it I have come up with an easier and more systematic approach that will save you time and possibly money. The systematic approach is to split the testing of the system into three parts:
a) The system downstream from the headlight wash/wipe control unit to see if the problem lies with the wiper motors or wiring from the control unit to the motors.
b) The headlight wash/wipe control unit itself
c) The system upstream from the headlight wash/wipe control unit to see if the problem lies with the service wash button, the wash interval control unit or associated wiring.
You will find it helpful to familiarise yourself with the components of the system by studying the wiring diagram near the end of this FAQ.
3. Check the system downstream from the headlight wash/wipe control unit.
The headlight wash/wipe control unit is fastened to the washer fluid container in the left front of the engine bay. The control unit looks like this…
Disconnect the wiring connector. Testing will be easier if you unscrew the control unit from the washer fluid container. There is a connector diagram on the control unit but it shows how the terminals are arranged on the control unit itself. This is the mirror image of the wires when looking at the top of the connector. The terminals look like this when looking down on the connector:
Operating the motors is fairly easy. With the usual care, connect a fused lead from the +ve battery terminal (12 V) to terminal 53 on the connector block. Then touch terminal 53a with another fused lead from the +ve battery terminal (12 V) for 2-3 seconds only. This should operate the headlight washer pump and cycle the headlight wipers for about 30 seconds, then shut off. If this works then move on to checking the system upstream from the headlight wash/wipe control unit otherwise check the wiper motors and the pump as follows.
Note: If you got fed up with the whole thing and wanted to operate them manually then you’d wire it up this way with a toggle switch on the wire you use to touch 53a.
Remove the covers over the headlights in the engine bay.
Disconnect all the connectors going to the headlights and the headlight wiper motors.
Remove the wiper blades and the front grills and then remove the headlights.
You can leave the wiper motor mounted on the headlight frame when testing.
Note that the right hand (facing the car) motor has 3 output leads (R, BL, BR), and the left has 4 output leads (R, BL, BR, and BL). The red is a 12 V (+ve) momentary on; the black is a 12 V (+ve) constant on; the brown is ground; and the blue on the left hand motor is an output signal to the washer pump.
To test each motor, connect a fused lead from the +ve battery terminal (12 V) to the black lead and a ground to the brown lead. With another fused wire from the +ve battery terminal, touch the red lead for 2-3 seconds only. The motors should cycle on for about 30 seconds, then shut off.
This isn’t easy to do because of the nature of the connector. I was lucky to have a cut off the wiring loom to use, if you don’t you’ll probably find it easier to rig something up to ensure you don’t short across the pins.
Test the output to the washer pump on the right hand motor by connecting a multimeter between the blue lead and a ground. Repeat the motor test to check for a change in voltage (up from the resting 0V) between the blue lead and a ground. It should come on for a second or two. If a motor isn’t working then replacement is the easiest option (Part #s 61631369105 / 61631369106).
To check that any of the pumps are working disconnect the wiring and connect a +ve to one terminal and ground the other. The pump should operate. If the pump doesn’t work then replacement is the easiest option. The headlight washer pump is the same item as the intensive washer pump and the windscreen washer pump (part # 61661368589)
If the motors and the pump work the problem must lie with the wiring. Check and clean all connectors and check wiring for breaks following the circuit diagram.
Reassemble and repeat the test for the system downstream from the headlight wash/wipe control unit at the control unit connector. At this point the system downstream from the control unit is now working. Now see if the system works when operated from the service wash button. If it doesn’t then there is another fault.
4. Check the headlight wash/wipe control unit
Without a working headlight wash/wipe control unit to swap in, the only way I can figure to test it is by simulating the feed from the wash/wipe Interval Control Unit (with the ignition and headlights on) by connecting the connector with the BR/GY wire on the intensive pump to ground. This should trigger the headlight wash/wipe cycle.
If not, then:
1. test that intensive wash pump is working,
2. check wiring and clean all connectors between the pump and the control unit.
If this still fails then the control unit is likely to be at fault. Replacing the control unit is the only option unless you have electronic skills beyond the ken of the author. If you can fix them I have two waiting for you to do.
The Part # is 61311367391. The control unit is about UK£60 from the dealer. Good second hand units are rare but not in great demand so expect to pay about UK£10 if you can find one. Be wary of untested second hand units though. I went through two to find one that worked.
5. Check the system upstream from the headlight wash/wipe control unit.
Check the service wash switch. Remove the lower cover from the steering column and disconnect the wiring connector to the stalk with the service wash button. Pushing on the button should connect TS (BR/BL) and PS (BR/GY). Test this is working by using a multimeter to check resistance, it should drop to zero when the button is pressed. There is no need to remove the stalk or the steering wheel to test. Replacement is the only practical option if it doesn’t work. (part # 61311369932 from 09/85)
Check the inputs to the control unit from the washer switches/button.
Check the Wash/wipe Interval Control Unit in the fuse box. It’s the big black box at the top. If your windscreen wipers work but the headlight wash/wipe system doesn’t then this is unlikely to be at fault but it can’t completely be ruled out.
The only way I know of to check the Wash/wipe Interval Control Unit is to swap in a known working one. I don’t know of any way to test it. If this is at fault then you would probably expect to be experiencing problems with your windscreen washers in addition to the headlight wash/wipe. (part # 61311367391 ).
If you have reached this point and done all the tests and your headlight wash/wipe system still doesn’t work then I stumped. All I can suggest is that you work through it all again. Sorry.
Wiring Diagram:
Even with this wiring diagram it is not immediately apparent how the system actually works. This is my take on it:
How I figure it works (references are to the circuit diagram):
• Terminal PS on the service wash button () is connected to the “Pump – Intensive Cleaning Fluid” (7) and goes to ground via TS to make it work.
• The ground via the TS terminal is through the “Wash/wipe Interval control Unit” (16). There is a timer in there that holds the earth via PS for a period of time to operate the “Pump – Intensive Cleaning Fluid” (7).
• This current through the “Pump – Intensive Cleaning Fluid” (7) triggers the headlight cleaning cycle through the “Control Unit for Headlight Cleaners” (1) which then:
i. Follows the intensive wash period by switching on the screen wash for a timed interval by earthing 85,
ii. follows this by switching on headlight wipers,
iii. which triggers the headlight wash,
You’ve probably already realised that I don’t really know what happens in the control units and that this is only what I think happens!
Reference Links:
Two topics on http://www.bigcoupe.com relating to E24 headlight wipers with similar electrics (but differing mechanisms)...
those pesky headlight wash/wipe bits....
Those pesky squirters II -revenge of the squirter...
Four topics on http://www.mye28.com on headlight wash/wipers…
Headlight wash/wipe troubleshooting (fixed)
headlamps cleaned up and wiper motors fixed!
Woohoo! Working headlight Wi/Wa system.
Headlight wipers -- 1985 535i US
Headlight wiper system
ETM Wiper/Washer and Heater washer jets (no headlight wash/wipe)
