[macnore]

I had my wiring harness replaced ( I had no rear wiper or backup lights) turns out the wiring harness was the problem. Once replaced all works fine; except

My problem now is the wiper won't automatically return to the bottom of the rear window. If I use it on intermittent it returns to the base of the window, but not if I turn it on any other setting.

Can wiper system be reset by disconnecting both battery post.(like rebooting your PC or router) I know this works to reset a check engine light. I am thinking this because the wiper blade stops where it was when the wiring harness broke and shorted out. I can just try it but wanted to share this because the service manager said the motor was wearing out. This I doubt I have a 1995 legacy wagon and the wipers all work fine. Subaru makes a better car than most. (I have owned Subaru since 1978) and someone else might have a different idea as to this problem.

 

[plain OM]

Did the problem appear right after the harness was replaced? If not, then how long was it between the harness being replaced and the problem first being noticed? (I'm wondering if perhaps the wiring has failed, once again.)

I'm not certain about the way the wiper is controlled, but from the wiring diagram there are several fuses that power the wiper system that should be verified. These are:

Fuse #8 in the engine compartment fuse panel;

Fuse #7 and fuse #23 in the in-cabin fuse panel (to the left of the steering column).

Fuse #23 powers the wiper as it returns to the parking position after the switch is turned off, and it also powers the rear washer pump -- have you tried the washer? If it doesn't run, fuse #23 might be blown.

(See the Owners Manual for fuse panel diagrams with fuse #s.)

 

[CNY_Dave]

Wiper motors usually always get +12V and the switch/intermittent circuit grounds the other (-) side of the motor, and then a commutator keeps the motor (-) side grounded until the wiper is in the park position.

So, of anything is funky with any grounds, the wipers can do odd stuff. there is a ground lead right at the wiper.

 

[plain OM]

Wiper motors usually always get +12V and the switch/intermittent circuit grounds the other (-) side . . .

Perhaps on some makes, but it appears to not be the case with Subaru. Attached is the 2005 wiring diagram for the rear wiper where the negative side of the wiper motor goes directly to ground and the 12 V supply is switched. I also checked a number of Subaru wiring diagrams from 1995 to 2011, and they're all the same ground side configuration.

In the attached diagram, FB-23 and FB-24 (at the top of the diagram) are switched 12 V lines that are powered when the ignition switch is at ACC or ON. When the wiper switch is turned to ON, pin C6 of the BIU is grounded. The BIU then connects 12 V to the motor from connector pin B1 to wiper motor connector pin 2. As the motor begins to turn, the internal switch moves from the Off or rest position (as in the diagram) to the other side, connecting the 12 V at motor connector pin 5 to motor connector pin 4, and from there to the BIU connector pin B8.

The motor internal switch remains "On" whenever the wiper arm is away from the parked position. Consequently, there's 12 V at BIU pin B8 whenever the arm is off park. Now, although I'm not sure how this works internally inside the BIU, as long as the wiper switch itself is at ON, the BIU continues to provide power to the wiper motor. However, when the wiper switch is turned Off, the BIU senses whether or not there's 12 V at BIU pin B8, and as long as there's 12 V there (coming through the motor internal switch), it continues to power the motor. But as soon as the wiper arm reaches the park position, the motor internal switch will toggle over to the Off side, opening the circuit from motor connector pin 1 (12 V) to motor connector pin 4 (to the BIU) and grounding BIU connector pin B8. At this point, the BIU cuts the power to the motor thereby stopping the arm at the park position.

In intermittent operation, BIU connector C18 is grounded by the wiper switch and the BIU powers the wiper motor, but in this case only for one cycle. Again, it uses the motor internal switch to signal when the wiper arm is back at the rest position after the first sweep at which time the wiper motor stops running. The BIU then waits a set time, and starts the single cycle over again.

The stopping point for the wiper arm is determined by the motor internal switch that's mechanically connected to the wiper arm shaft drive mechanism, and it's the same whether the wiper had been running with the wiper switch in the Intermittent or On position. (This makes the OP's description somewhat puzzling to me, as it should be the same. See http://www.subaruoutback.org/forums/66-problems-maintenance/20718-rear-wiper-does-not-return-park-home-position.html for a previous case.)

Incidentally, the use of the BIU adds an additional feature -- when the rear wiper is in Intermittent operation, if the transmission is set to Reverse gear, the BIU will run the rear wiper continuously instead of stopping after each sweep.

 

[CNY_Dave]

That pic isn't so clear to me, looks like the switch connects various leads to ground to activate the wiper etc.

 

[Novablue]

There are so many connections there is a lot to go wrong there. It would be nice to see what is actually happening. It almost sounds like the harness got plugged in wrong or is the wrong one.

Don't discount the fact that the motor is going out. It's 17 years old. Personally I too would do more checking before replacing it.

 

[plain OM]

That pic isn't so clear to me, looks like the switch connects various leads to ground to activate the wiper etc.

The diagram shows the motor internal switch in the "rest" position, that is, with the wiper switch Off and the arm at the proper location. In that case, the switch is connecting pin 4 of the motor connector to pin 3 of the motor connector, which goes to ground. This is the only ground connection through the switch, and this is only in the "rest" position.

The motor itself is connected between motor connector pins 2 and 3. As pin 3 is wired to ground, in order for the motor to work, 12 V has to get to pin 2. The motor internal switch isn't connected to pin 2. So the 12 V has to come from the BIU (BIU connector pin B1). As soon as the motor starts to run, the switch toggles over, so that the ground connection in the switch (lower side going to motor connector pin 3) does nothing. But the then continuity between motor connector pins 1 and 4 (through the toggled internal switch) provides 12 V from FB-23 to BIU pin B8.

 

[plain OM]

It almost sounds like the harness got plugged in wrong or is the wrong one.

Indeed. That's why we need to know if the problem appeared shortly after the harness was replaced, or a good time later, with the wiper operating properly in between (although I would hope the operation of the wiper would have been checked when the harness was replaced).

 

[CNY_Dave]

BTW if it is the wrong harness, if the right set of circuits is energized (or de-energized) a short to ground could be created.

 

[wilsonhp]

BTW if it is the wrong harness, if the right set of circuits is energized (or de-energized) a short to ground could be created.

Which should instantly blow fuses....

 

[CNY_Dave]

"Should" doesn't apply to the vehicle I had to fix once-upon-a-time, good chunk of the wiring harness smoked... funky sneak circuits can cross high-amp circuits over to lower-amp ones, high-amp circuit fuse doesn't mind at all!

Hopefully things have improved since then though.

 

[04MSM]

These cars are notorious for breaking wires in the harness where it goes between the body and the rear hatch. I did the repair on mine this summer. I don't recall which wire it was, but it was not at all obvious from the wiring diagram. The park system is more complicated than just a cam breaking the circuit at the right place and the motor stopping. I'm pretty sure there is a computer control module involved in it as well.

If the repair involved a new harness, it doesn't seem likely that it would have a broken wire, but it might be a bad connector at one end or the other. Some time with a jumper wire and a Volt/Ohm meter will probably sort it out, but it is a pain in the neck. You need to take a lot of trim panels off from both the rear gate and the right side rear behind the window, to get to all the connections. If you need to know how to get them off, send me a note and I may be able to find the email I had with the trim removal diagrams.

 

[plain OM]

04MSM

This is one of the related threads with similar, but not identical rear wiper symptoms. You contributed to it:

http://www.subaruoutback.org/forums/66-problems-maintenance/20718-rear-wiper-does-not-return-park-home-position.html#post422486

I'm pretty sure there is a computer control module involved in it as well.

The BIU (a microprocessor/LAN router) is clearly involved, but I haven't found any evidence of it actually having any software-driven control function pertaining to how/when the rear wiper parks that is independent of inputs from the rear wiper switch, the rear wiper motor internal switch, and the transmission control (reverse). Rather, it seems to act only as an on/off switch reacting to those inputs. But I'm always open to learning, and if you have any insights that would help clarify this, it would be much appreciated.

In the meantime I await a reply from the OP; I think we need some clarification of the symptoms and the time frame regarding the harness installation and the appearance of the problem.