Second try at 230TE rear wash not working.

[Brian23]

I have re submitted this as there seems to be some confusion over the problems. Also I do not see the need for others to hi-jack the thread with their own problems when there is plenty of forum space.

Original Thread

Hi, I have eventually tried to find out why my rear wash does not work. when you press the button the wiper goes but the wash will not. i connected the motor to the battery and it works ok. When I put a circuit tester (light type) it glows on and off in rhythm with the wiper. Any ideas

Brian

Then I wrote.

I think that there is a bit of confusion to the symptoms. When the wash wiper button is pushed and held in, and a neon type circuit tester is applied to the power line for the washer motor, the light goes on and off as the wiper goes across the screen and back. The button is not released, so I would expect the power to be continuous so that the water is continuous.
Brian

 

[Number_Cruncher]

I think that by using a tester which draws only a small current, you may be confusing yourself a bit. Try using a test lamp with a decent sized (12v 21W type 382 indicator bulb say), to draw some current, and I very strongly suspect that you won't see it light.

If so, the symptoms point to a chafed barely connected wire in the hinge area, or, much less likely, a bad connection at a terminal block. That you can see some correct function with a lamp which draws but a tiny current is encouraging - it means the systems is fundamentally working, but, with a high resistance.

 

[television]

Always test using a meter or load otherwise its meaning less, a bad ground is just as likely

 

[Number_Cruncher]

>>Always test using a meter or load otherwise its meaning less

I'm going to be pedantic - please forgive me Malcolm.

It's very easy to mislead yourself taking voltage readings with a meter - the high resistance of the voltmeter means that it draws very little current, and can behave just like the high resistance test lamp used by the OP.

It's OK if you measure the voltage across the still connected device, because the device will have a low resistance compared with that of the meter.

If the dis-connected wires can light up a 21W bulb, usually, that's enough on most circuits (obviously, you have to do something a bit beefier to prove circuits like glow plug supplies).

So, there's a distiction on how you might best test the circuit, depending upon whether the load is connected or dis-connected. Brian, were you testing across the dis-connected wires with your tester?

(Sorry Malcolm - I know that you know all of this backwards - it's for the OP's benefit)

 

[The Crooner]

Brian

I'm sorry if we hijacked your thread - it was mostly related and no malice was intended.

Since we've started again, let me reiterate what I know with the benefit of experience.

The washer fluid does not pump continuously onto the rear screen when activated.

Rather, the control of the washer pump is delegated to the wiper circuit, and for each complete iteration of the wiper - ie there and back, the pump will be on for only half of that time. The result being an intermittent voltage applied to the pump, which it looks like you are getting.

If you have water coming from the jets then your washer is working as MB designed it.

If you have no water from the jets you have other problems.

Can you clarify exactly what happens at the minute and we will try and help further.

Tony

 

[The Crooner]

Brian, do you have two buttons on your dash, one for wiper, one for wash?

Tony

 

[Brian23]

Thanks again

Thanks again for the replies and I did not think that there was any malice intended by talking on other subjects.

1) Ok there are 2 buttons on the dash. 1 for wipers and 1 for wiper/wash.
2) There is no water at all and the motor does not run at all, but will run when connected direct to a live power supply.
3) On connecting a stop/ tail light directly to the power plug (Disconected) for the motor it will light the duller light, but not the 21w stop light. I have checked that both work.

 

[television]

The washer pump consumes more than 21 watts

I will try and look at the wiring diagram tonight.

 

[The Crooner]

Then it looks like you have a wiring issue from the rear wiper to the pump.

I would take a live from the battery, and a lead from the switch and wire the pump direct to the switch via a relay.

You will then have a permanent spray whenever the switch is activated.

To do the job properly you will need to remove the passenger seat, the passenger rear sear, and various bits of trim/carpet.

Tony

EDIT

You might be able to trace the feed from the switcgh if you can find the colour codes.

If you have a towbar you will also have a permanent live somewhere near trhe spare wheel.

All of the front to back wires run in two ducts, one on each side of the car under the carpets.

 

[Number_Cruncher]

Thanks again for the replies and I did not think that there was any malice intended by talking on other subjects.

1) Ok there are 2 buttons on the dash. 1 for wipers and 1 for wiper/wash.
2) There is no water at all and the motor does not run at all, but will run when connected direct to a live power supply.
3) On connecting a stop/ tail light directly to the power plug (Disconected) for the motor it will light the duller light, but not the 21w stop light. I have checked that both work.

If it won't light a 21W bulb, then, you have a high resistance somewhere in the circuit.

To effect a proper repair, you need to find where the high resistance is, and repair it. To find the high resistance, you need to find where the voltage is being dropped.

Take a voltmeter - or your neon tester; with everything connected as if in-use, pleace the + end of your tester onto a known good positive supply, and the negative onto the positive terminal of your still connected motor (backprobe through the terminal). Work the washer switch. If the lamp lights, the high resistance is in the section of wiring that your tester is spanning. If the light doesn't light up, the fault is elsewhere.

To test the earth side, for example, place the positive side of your tester onto the still connected earth terminal on the washer motor, and the negative side of the tester to a known good earth. Work the washer - if the lamp lights, you have an earth fault. If the lamp stays off, the earth is OK.

The fault is almost certainly in the hinge between the body and the tailgate, and it's almost certain that there will be more than one damaged wire.

 

[The Crooner]

To effect a proper repair, you need to find where the high resistance is

He is right, I suggested a bodge.

Best of luck with the wires going through the rubber hose from tailgate to interior, its in there they will be broken, just as my screen wash hose was.

Tony

 

[television]

One snag with using a meter is that you must know what you are measuring.

Take the pump as an example, if the pump has 12volts on one connection, it will have 12 volts on the other terminal if it is not grounded on that terminal, as sometimes the ground is switched.

It is the same as with a light bulb, put 12 volt on 1 pin and the other will measure 12volt too

 

[roofless]

this might help http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1990/300TE/SYSTEM WIRING DIAGRAMS/3641.pdf this is from a post on the same fault by mercedes190e it could help others to help you

 

[television]

Thank you roofless,,,there is nothing on my files