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...I understand from reading previous posts on this and other threads that the second wire from the top is the power supply that parks the wipers when the switch is turned off. In a document someone posted years ago (thank you) called Bosch Terminal Designations the wire that parks the motor is described as "Wiper (+), self-parking switch off". I am trying to determine when this wire is supposed to be energized.
I don't know about your wiper motor specifically, but normally there are 3, or 4 terminals:
1) Ground (-) - This may be the motor frame itself, grounded thru the vehicle steel, not necessarily a terminal.
2) Self parking (+) - This should always be connected to the accessory power and live when the ignition switch is in the "on" and "accessory" positions. This supplies power to the motor when you switch off the wipers and is internally interrupted when the wiper returns to the park position. If you just applied power to this and the wiper is already in the park position nothing will happen. If the wiper is anywhere else the wiper will cycle to the park position. (Sometime on newer vehicles this is the actual and only power supply, 3/4 are just signals to start.)
3&4) Low speed/High Speed/Intermittent/Wiper (+) - Varying names and attributes, but these all start the wiper in motion and should be connected to the appropriate wiper switch position.
 

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Thank you for the great explanation choprboy. To elaborate a bit more on the Unimog motor wiring.

There are 4 wires:

1. Ground: I know this is working as the wiper motor works when power is applied.

2. Power (+): I know this is working as the wiper motor spins when switch is set to "on" and when set to "interval".

3. "Wiper (+), self-parking switch off": I have no power here when the wiper is in any position on the windshield and the accessory switch at the key is on.

4. "Return line to negative battery terminal or ground, via switch or relay (switched negative)": I don't know the purpose of this line and I am unable to test it as the linkage to the wiper arms knocks my probe off the terminal when I activate the wipers. Could this be what allows the wipers to have an interval setting by cycling the ground instead of the power? Or do you think it has something to do with the park function and the source of my issue?


Thanks again,
BWSwede
 

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Hmmm... I think you have me a bit stumped on #4 BWSwede. I have never seen one like that and I am at a loss to explain its function from the description. I have no idea why there would be 2 grounds, one of them switched.
 

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Well... Now you have got me all confused.... After a bit of research I've stumbled onto another wiring setup, which seems to have been used on British (MGs, Lucas, etc), older Fords (pre 80s), VW, etc. that would have 5 terminals. 1) Parking (12V input from the battery), 2) Parking switch output (power out from #1 when in any position but park), 3) Low speed, 4) High speed, and 5) Ground.

This setup required a 3 position 4 terminal wiper switch that in the "off" position connected the #2 output to #3 low speed input. Or alternately in wiper "low" or "high" it connected the #3/#4 to a separate 12V source.
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Could your #4 "Return line to ground" be a mistranslation of some sort and it is actually the output from the park switch in the motor and you only have one speed? Something like this?
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Apparently you should ignore everything I said in the post yesterday... cause I am an idiot. Looking at a few examples of modern wiper motors, it shows the parking terminal connected to power only when switch is in the "off" position. That is not what I remembered...
2617713
 

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Thank you for posting the schematics, unfortunately I am unable to understand them. I'll look up the symbols and see if I can determine how the switches function.

The descriptions of the terminals are from a Bosch electrical device number decoder document. Perhaps it doesn't apply to this motor.

To clarify, the wipers may be called two speed by some but they are actually a single speed (the motor always runs the same speed) but there is a about a 3 second delay between the wipe cycles when set on the delay position.

The switch has 3 wiper positions, off, continuous, and delay (and actually a fourth position if you count the washer pump activation).

Between the switch and the motor is a relay. I think this is where the delay function is performed. I don't know how the relay would know to operate the motor for exactly one revolution when on the delay setting. It seems to me instead that the relay would briefly power the wiper motor every 3 seconds and a park feature in the motor would end the cycle when the wipers are at the bottom of the windshield. If this is the case, I don't understand why the park feature wouldn't work when the wipers are on the continuous setting?

I have attached a schematic from the shop manual that shows the wiper relay and wiring (this option is not shown on the electrical schematic on the blue glove box size manuals that I have). Hopefully the schematic diagram on the motor means something to you.


I really appreciate your help.

BWSwede
 

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Ah, OK, that helps a lot, and my first instinct was correct, the park should be connected to power.

In my diagrams above, the wiper switch is the dashed box in the upper left (I didn't realize or understand that you also had a relay installed). The bottom dashed box is the wiper motor; the motor is circle in the left of the box with motor brush top and bottom (and a third low-speed brush at 10 o'clock) and the motor cam that activates the parking interrupt switch is to its right.

In the wiring diagram that you provided, you can see the parking interrupt switch built into the assembly, just without the cam shown. Similar to the first and second circuit diagrams above. The wiper is in the parked switch position in the diagram.
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The diagram is very helpful (if correct) as it shows both the terminal designations (standard relay terminal markings) and the wiring colors. If I am reading the diagram correctly, there are actually 3 different options for the wiper control shown (unfortunately is doesn't have the part key to confirm). There is possibly a 4th option for a remote switch or signalling, but it is cut off the diagram.:
  • The most basic would be using only part #12, a one "on" position switch for the wipers.
  • The second option would replace #12 (I believe) with #6 and #7, a switch and relay for "on" and "intermittent". The intermittent function would be provided by the relay turning on/off at a regular interval. The internals of the relay are not shown.
  • The third option would be #11, a time delay relay to continue wiper option after activating the washer pump.
I think the 3rd option could be used with the 1st or 2nd, but the 1st and 2nd are exclusive of each other. I believe your wiring diagram for the switch/relay would look like this:
2617743

  • A 1.5mm green/red wire should run from fuse #8 to terminal 53a (parking) on the wiper motor, this will power the motor whenever it is not in park. Note the diagram shows a second optional green/red wire coming off terminal 53a which has no endpoint, it is unclear to me if this is disconnected from the fuse or not when option 6/7 is in play (I think the primary wire should always be connected to the fuse).
  • A 1.5mm brown wire runs from terminal 31 (ground) on the wiper motor to a frame ground.
  • A 1.5mm black/green wire runs from fuse #8 to the dash switch (the switch also has a brown wire to ground.
  • Unfortunately the switch is not marked: - a brown wire runs from the switch to terminal 31bS on the relay (this is probably ground for the relay coil), - a black/red wires runs from the switch to terminal 53b on the relay (this is probably the intermittent-timing-enable signal), - a black/purple wire runs from the switch to terminal 53 on the relay (this should be wiper "on")
  • A black/purple wire runs from terminal 53 on the relay to terminal 53 on the wiper motor (this should be the run signal).
  • A black/brown wire runs from terminal 31b on the wiper motor to terminal 31bM on the relay.
There are a couple different ways to do it (hard to know because of the missing relay internals and cutoff stuff on the sheet) but I think this is the way it works:
  • Terminal 53a on the wiper is always connected to power via fuse #8. If the wiper is not in park, it will cycle and stop at park (where the internal switch breaks the motor positive lead from 53a). When parked the internal switch effectively grounds terminal 31b (that weird "switched negative") via the motor winding. This serves as a ground reference for other relays/timing devices.
  • Power from fuse #8 is also supplied to the dash wiper switch. When the dash wiper switch is "on" it supplies power to terminal 53 on the motor (jumped thru terminal 53 on the relay) to run continuously until power is removed (at which point the motor will park via 53a).
  • When the dash switch is in the intermittent position it supplies power solely to terminal 53b (not 53) on the relay. If the relay senses ground on terminal 31bM it will start a timer and then connect terminal 53b to terminal 53 internally when the timer expires. This sends power to the wiper motor and it starts a cycle, which removes the ground reference from terminal 31bM, reseting the timer. When the wiper motor parks again, ground on 31bM will be reasserted and a new timer cycle starts.
If you have the #11 washer option, when you activate the washer pump (regardless of whether the wiper function is on or off), it also activates the #11 time delay relay. This relay connects power from fuse #8 (via a 3rd black/green wire from the fuse to the relay) thru to terminal 53 on the wiper motor (via a 2nd black/purple wire). The wiper motor will continue to run until the delay relay turns off, sometime after the washer pump is stopped. (Edit: looking at it again, #11 might be a separate time-delay push button as well).
2617744

I think I can give diagnostics instructions to test/measure the point if you need.
 

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Choprboy,

Thank you very much for the detailed explanation on how the wiper system works and the various options available. I believe the dashed lines are for the optional equipment and in this case (the intermittent wiper) my truck is so equipped.

Following the dashed lines it looks to me that with the intermittent wiper option the power to run the motor and the power to park the wipers goes from the fuse to the switch, to the relay (where the power gets split) and then to the motor. It also looks to me that a good way to bypass the relay is to wire it like you show in your schematic where you run power directly from the fuse to the park tab. From what you describe above I gather that if I temporarily wire it like you have shown and the wipers park, then I know the relay is bad.

My questions:

1. Should the power to the park tab always be hot when the key is in the accessory position (regardless of the switch position)?

2. Should the power to the park tab only be hot when the key is in the accessory position and the switch is off?


Thanks again for the thorough lesson on wiper motor wiring. I think I am getting close to understanding how it works and hopefully getting it to work properly again.

Best,
BWSwede
 

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Yes, I agree... I think the dashed lines indicate the optional components. Since they include all the options at the same time, it kind of hard to know if solid lines to the standard components (that get replaced by the optional ones) are completely removed or not.

I think there should be 2 power wires from fuse 8 to the wipers (plus possibly other wires to other accessories). One wire should go directly to the park terminal on the wiper. I think it should be hot to park the wiper whenever there is accessory power, regardless of the switch position. (It should internally disconnect from the motor when the wiper reaches the park position). The second wire should go to the dash wiper switch.

I think this is the way to test the wiper motor:
  • 1) Disconnect all 3 power/signal wires from the wiper motor (leave the brown terminal 31 ground connected to frame ground).
  • 2) Use a jumper to connect fuse 8 (or something else fused just in case...) to the park terminal, 53a. If the wiper is not parked, it should cycle to park.
  • 3) Use a second jumper and connect fuse 8 to wiper terminal 53. The wiper should start running continuously. Disconnect the jumper and the wiper should run until it reaches the park position and stop. You can then "test" intermittent by momentarily pulsing terminal 53 again (~.5sec or so, until the wiper starts moving), then disconnecting terminal 53. The wiper should complete 1 wipe and stop.
  • 4a - optional) If you disconnect the jumper to park terminal 53a and connect wiper terminal 53 only to power, the wiper should cycle but immediately stop in place when you remove power. Reconnect 53a to cycle back to park.
  • 4b - optional) With the wiper parked, remove all power from the system. Use a multimeter to measure resistance between the ground terminal (31) and park terminal (53a). The circuit should be open (many Mohm). Measure the resistance between ground and the "switch negative" terminal (31b). It should measure a couple ohms (resistance thru the motor windings).
If all that works the motor is good. If it doesn't run and park as expected... then either the park switch is damaged or we've got something wrong in the wiring diagram. If you do not have continuity between ground and "switched negative" 31b when parked (#4b)... then the park switch may be bad (and intermittent wouldn't work).

To test the relay I think you can do the following:
  • 1) Reconnect the wiper motor terminals to power/relay per the drawing.
  • 2) Disconnect all wires between the relay and the switch (leave the wires between the relay and wiper motor).
  • 3) Connect a jumper from terminal 31bS on the relay to ground.
  • 4) Connect a jumper from fuse 8 to terminal 53 on the relay (this should already have a wire connected going to terminal 53 on the wiper). The wiper should start cycling normally. Remove the jumper and the wiper should return to park.
  • 5) With the jumper from #4 removed and the wiper parked, connect a jumper from fuse 8 to terminal 53b on the relay. The wiper should run intermittently until the jumper is removed.
If #4 doesn't work, there is some problem between the relay and motor. If #4 works, but #5 doesn't, I think the relay is probably bad. (NOTE: There is another possibility here, but it is complicated, so I'm going to pass on explaining it for the moment). If #5 works, then the problem may be in the switch or switch wiring.

To test the switch:
  • 1) Disconnect the wires between the switch and the relay. Leave the switch ground and power from fuse 8 connected to the switch.
  • 2) Using a multimeter, with the switch in "on" you should read +12V (or is yours +24V?) on the switch terminal that would go to relay 53. No voltage should be on the switch terminals that would go to 53b or 31bS on the relay.
  • 3) With the switch in "Intermittent" you should read +12V on the switch terminal going to relay 53b. No voltage should be on the switch 53 or 31bS terminals.
  • 4a - optional) With the switch in "Washer" you should read +12V on the terminal to the washer. You may also have +12V on either or both 53 and 53b (no switch details so guessing...).
  • 4b - optional) Remove all power from the system. With the switch in the "Intermittent" position, measure resistance between ground (the brown wire) and the switch terminal to 31bS. You should get 0 ohms.
  • 4c - optional) Repeat the above measurement with the switch in the "On" and "Off" positions. You may get 0 ohms or open circuit (related to the possible complications noted above).
If #2, #3, and 4b check out, then the switch is probably just fine. If #4b doesn't work then uggg...

[Butt covering section] Take everything I'm saying with a grain of salt... I'm learning/guessing/intuiting from the circuit diagrams and past experience too... Never laid hands on this particular setup. [/Butt covering section] phew...
 

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I was about to start Choprboy's test procedures to see if I could determine where the fault lies. To test the park function I reached in to the area with my longest needle nose pliers to disconnect the fitting. When I pulled it sort of jerked off and it pulled two other connections with it. I looked at the schematics and Choprboy's notes and tried to determine the best I could where each wire went. I then went around the front of the truck and removed cross bay corrugated duct work and the rubber hose from the snorkel. I was able to reach my arm in there and with the help of a long screw driver was able to push the fittings back onto the tabs.

Once I was sure I had everything back in place in the correct order I tried to the wipers to see if any fuses would blow due to the connections and to my surprise the wipers became fully functional, including the park function. I don't know if there was a wire that was disconnected (very difficult to see the connection points once the motor is installed) or whether something was hooked wrong. Per a PM Choprboy thinks it may have been that the switched ground (not visible from the cab) may have become disconnected while wrestling the motor into the mounting bracket.

The only thing left for me to do on this project is to index the linkage attached to the motor shaft so that the wipers park at the bottom of the windshield.

Thanks again for all the help provided by the forum members.

BWSwede
 

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I had the same problem on my 406 after I pressure washed it one day, it was the relay had a burnt terminal. the relay is located up above the air filter closer to the side wall of the dash, I bought a spare at the time, but ended up just running the wiper on a normal switch when I got rid of the multi function key switch.

if you want the new relay I still have it in the Mercedes box, ill sell it for like half price lmk

Otherwise you can also use the wiper motor with no relay it basicly works the same, just no auto reset to center...
 

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Thanks Snow mogg. As it turned out my relay was good. It was the motor that was bad. It has been replaced and everything is functional again.
 

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I've had one of my wiper arms stripped off of the post when heavy wet snow crashed down on it when I was not around (before snow I typically swing the wipers out to assist with snow removal later on IF I'm around). So I unplugged and insulated the park terminal and now just have to time when I shut off the wiper switch to get them to stop where I want them.

Typically this is in the up position. Stopping them when pointed up also helps cut down on the amount of crap that builds up on them, such as pine needles, which come with sap. I have had my wipers glued down before after sitting for awhile in the down position. Also lots of debris builds up on them (wood chipper chuff, sawdust, plain old dirt, tree droppings, etc.) and they don't work well when actually needed due to the crud on them. With them up, stuff can't build up on the shelf and the rain washes off anything that does attempt to hang on.

Of course my truck lives in the woods so not all parties may care about these problems.

Just sharing in the event that some one lives the same dream I do.
 

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That's not a bad idea. Fortunately my truck is able to stay indoors until its use is needed. For those rare times it does stay outside during winter it sure would be nice to be able to switch the park function off.
 

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Park is constant power on so you could just install an in-line switch in the wire and be able to have it park when you want it to and not when you don't. Best of all worlds!

Someday my truck will live at least under cover if not actually indoors. Barn construction is in progress now.
 
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