Another problem has surfaced with our beloved 91 volvo 240 wagon.
The wife came home last night and informed me the rear wiper acting
funny. It seems that in the constant run position, it operates ok but
will not return to the preset default position. In the Interval position on
the stalk, it will run for about a second or so and just stop. When I
press the washer button on the stalk it will sweep for almost 3 cycles
and stop somewhere other than where its suppose to.
Looking at the diagrahm for the rear washer/wiper , I hold suspect the
rear wiper relay. I have to believe that the diode/cap in the motor
section has to be ok since the motor is cycling ok when in the on
position. Any idea's??

 

Take off the rear cargo gate cover and see what's going on. Probably some of the bolts are loose.

 

the wiper gets two power wires. one is always powered, and the other is powered when you turn the wiper on. inside the wiper motor assembly there's a rotary switch that connects that always-on power to the motor if the wiper is anywhere but in the home position, so for intermittent operation, you give it just a short pulse of juice on the regular wire, that moves the motor past the home position, and then that rotary switch keeps supplying it with power til its back home, where it shuts off.

its possible that always-on wire is broken or disconnected. its also possible that rotary switch inside the wiper motor assembly has gone sketchy (mine is spastic on its way home and herks and jerks til it gets there).

I believe the black wire at the motor is the 'always powered if the car is on' wire, while the green one is the 'powered when we want wipers'. these wires change colors at a connector somewhere in the tailgate (right side I believe) which goes up and over the right side tailgate hinge... up there, its a yellow-black wire for the 'always on', and its still a green for 'on when we want wipers'.

the diode and the capacitor are to reduce electrical interference from the motor and to keep 'counter-emf' from jamming the relay. if that diode dies, the motor doesn't run at all ever.

 

Thanks for the replies. Will check tightness of bolts, along with proper voltage
on the wires back at the motor. The prospect of that rotary switch going faulty
sounds right in the ballpark. Glad this website is around.

 

the most likely place for a failure, IMHO, is at the hinge where the wires have to flex.

 

MIne does the exact same thing. I keep on plying with the wiper til I get it where I want it to be. some times I keep it @ 12o'clock cause it just looks cool.

 

speaking of rear wipers, my son (22) has a 'mcnabb' border collie (thats a shorthair b.c.), hyper spastic dog that he is, barks if he's within a 1/2 mile of a cow or another dog etc.

well, he goes effin NUTS at the rear wiper when he's in the back of my wagon. tries to bite it through the glass, I think he thinks its a stick or something. its pretty funny, except then he starts trying to trash the interior trim.

 

Thanks to all for your interesting input to my problem. The problem with the rear
wiper was a broken wire at the tailgate hinge. The black wire in the 4 wire cable
was cut thru and the gray was about ready to go. Those are the two wires for the
rear wiper. The blue and yellow are for the tailgate lock. Volvo left plenty of cable
in the tailgate to feed back up thru the hinge. I was able to cleanly cut all wires
then solder and apply electrical tape. Also a little clear caulk around connections
helps to keep the solder joints from getting corroded. Rear wiper is working well,
plus the automatic tailgate lock is now working. That had stopped working awhile ago
and always had to go back and use the key in the tailgate lock. Either the blue or
yellow had to have been broken. While I was at it also took care of the left side of the tailgate. The center brake light was always working but the window defogger had not been working for a long time. I now have the window defogger back. Not a bad day.
Thanks again for the assistance.

 

if you spliced the old wires where they broke, I hope you did some really gnarly splices, as that's the place that gets the most stress. and you can't just use cheap ordinary wire there, you'll note the harness that goes over the hinge is made with fine strand wire to be flexible.

 

Because Volvo gave sufficient cabling in the ceiling , was able to pull 4-5 inches out of
the ceiling. I did not want to drop the ceiling. As a consequence the spliced area is
not in the area of stress but rather 2-3 inches past that point. Am planning on ordering
cables from FCP this week. Now there's the matter of finding out how to drop the ceiling in that rear area...

 

Just got this old 245 and it had all 4 wires in right tailgate hinge broken. Pulled back head liner and Replaced wires through hinge, into tailgate to central lock and wiper motor. Lock now works and wiper motor worked for about 45 seconds. I tested intermittent mode and regular wipe mode and both worked for a few cycles then the wiper was irratic and stoped with a puff of smoke. Removed motor and saw diode was burned up and was most likely the puff of smoke I saw. Opened motor and saw the spring that holds the brushes against commutator had fallen off. No other obvious damage. Reconnected spring and tried to get info about the diode but no luck. Read on some forum that any large diode would work. Robbed one off an old power supply and used it. When I activated the wiper switch the wiper motor turned on but only in regular mode and would not shut off until ignition key was turned off. Then turns on every time key is turned on. Had to pull fuse #1 to get it to stop running. I don't know if my problem is the wronge size diode or some thing else. Inspected rear intermittent relay, opened it up, no burnt parts in it, looked like new. Any ideas?

 

any possibility you connected the diode backwards?

or that you connected one or more of those hinge wires wrong?

btw, the wires through the hinge are special high flexibility wire with extra fine strands, if you use some generic hookup wire it may not last very long.

 

Pierce
I didn't know about FCP Euro and the replacement wire harness so I used some 4 wire trailor cable (yellow,green,brown,white) and made a new 4' long harness myself. The old harness used yellow and blue for the central lock and brown and gray for the wiper motor. I had to use yellow and green for the central lock and brown and white for wiper motor. The central lock works fine now so I know those wires are correct. The wiper motor worked for about 1 minute , I tested both the regular and intermittent modes. Both modes worked fine and then the motor became erratic and puffed some smoke. I pulled ignition key immediately , then pulled negative cable off battery. Removed rear wiper motor from tailgate and saw diode was smoked. Opened the bail and removed cover from motor,saw the spring that holds brushes against commutator had fallen off. No other damage to internals so I reattached the spring and closed up motor. Did not know VALUE of the diode so removed and replaced it with a bigger one I had in the shop. I soldered it in with the cathode on 53 and anode on 31b. I checked continuity after it cooled off. AOK, the gray wire (white) is connected to 31b and is the "signal" wire. The brown wire is connected to 53a and has 12 volts at all times. Chassis ground is connected to 31. In this configuration the wiper motor turns on and will not stop until key is turned off. Will resume running as soon as key is turned back on. Only way I can get wiper to RESET is to disconnect battery

 

I checked to make sure ground was good on 31, it is. Just for the heck of it I disconnected brown wire (constant 12v) and found that the rear washer momentary switch at end of stalk turned on washer and wiper motor until I released it, then washer stoped and wiper ran 3 more cycles and then it stoped but didn't park correctly. I know motor works. I'm sure diode is installed correctly (it's physically larger that original diode) and I'm sure it's wired correctly. What I don't know is why it won't stop running when it has the constant 12v applied. I'm thinking the park circuitry is the problem but not sure how to check that.
Jay