Wiper Motor Diagnosis Question
11-01-2004, 09:53 PM
#1
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Thread Starter
Wiper Motor Diagnosis Question
The wipers on my 1986.5 928S do not work. I tested the fuse and it seemed to be fine. After a mighty struggle, I pulled the wiper motor (and assembly) off tonight. What do I do now? I would like to ensure that the motor is receiving power. I'm looking at the Body Wiring Diagram and see the wiper motor and the six inputs/outputs, but which ones should I put my multimeter on to test for proper input voltage? I can read the numbers 1-6 on the female power connector that goes to the motor. Also (dumb question coming here) what would that voltage be? 120VAC?
Any help would be much appreciated.
Any help would be much appreciated.
11-01-2004, 10:36 PM
#2
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With the key on Acc., there should be 12v DC between the ground (larger brown wire) and one of #53 [green/black], #53b [green/yellow, or #53i [black/blue] with the wipers turned on.
Yes, only 12v - and be sure to set the meter to DC : test between the battery hot terminal on the passenger side fender well and chassis ground. Not sure how you tested the fuse - but if in doubt, swap it out for a trial).
Yes, only 12v - and be sure to set the meter to DC : test between the battery hot terminal on the passenger side fender well and chassis ground. Not sure how you tested the fuse - but if in doubt, swap it out for a trial).
11-02-2004, 12:26 PM
#4
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It also may be the relay which is not sending power to the wiper motor . On your 86.5 it is the third form the left on the second row of relays. part number 928 615 101 00 . When you turn on most switches in a 928 all it does is send a signal (low amp 12 v) to a relay . The relay is an electromagnetic switch and the relay switches on the power (high amp 12) which makes the motor or device actually turn on. That particular wiper relay has the delay intermittent function inside which means it has the ability to decide if and when it will power the wiper motor also even after you turn off the switch the relay continues to power the motor until the wipers return to the REST position. That is why there are several wires to the motor to tell the relay when the motor is in the correct rest position so it then turns off the power.
11-02-2004, 12:47 PM
#5
Burning Brakes
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My wipers stopped working awhile back on my 86. I pulled the plug from the motor and figured out that the motor was getting power, but wasn't moving the wipers. I thought the motor was dead, but it turned out that the bolt that connected the motor gear to the wipers was binding and not letting the wipers move back and forth...no movement at all. I did begin to take the motor out before I checked that bolt/nut, thinking that the motor was shot. Luckily, it was an easy fix.
11-02-2004, 08:19 PM
#6
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Thread Starter
Again, thanks Jim & John for the tips.
I found the proper voltage on the electrical connector (12VDC) and it moved to a different pin when I switched it to intermittent. I went ahead (don't know if this was smart or not) and connected the motor directly to the car battery with some cables. It made a very faint sound almost like a bug moving inside or a metal spring being crinkled. It didn't work. A bad coil perhaps? The wiper assembly seems to move fine. So, am I safe to assume it's the motor? Do those fail very often? Should I try to take it off and look inside? (Those screws holding the motor to the assembly are impossible to remove!)
On another note, I got the rear hatch release adjusted today using some tips from the Nichols page. Yeah!
I found the proper voltage on the electrical connector (12VDC) and it moved to a different pin when I switched it to intermittent. I went ahead (don't know if this was smart or not) and connected the motor directly to the car battery with some cables. It made a very faint sound almost like a bug moving inside or a metal spring being crinkled. It didn't work. A bad coil perhaps? The wiper assembly seems to move fine. So, am I safe to assume it's the motor? Do those fail very often? Should I try to take it off and look inside? (Those screws holding the motor to the assembly are impossible to remove!)
On another note, I got the rear hatch release adjusted today using some tips from the Nichols page. Yeah!
11-02-2004, 08:30 PM
#7
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How long has it been since the wipers have been in use? If a long time, the most likely culprit is oxidation on the brushes and stator of the motor. It sounds like the motor is trying to move, making a kind of UUUUUrrrrrrrrrrrrrrrr, hum noise. It can get juice to the windings, but not enough to set them in motion. first, try accessing the motor without the conommitant drive mechanism, and put the shaft in a drill and spin it for a while. Try to follow the correct direction of rotation. Then, apply 12V again to the plug and ground the ground line.
If the motor spins slowly, it's getting cleaner, if it doesn't spin on it's own, you must disassemble the motor and clean the brushes and stator (round, copper thing, with multiple segments) with 800 grit sand paper.
As per a previous post, lock for any binds or drive kinks that may stop up the works. I've had this problem on several old cars, and it's just from lack of use in most cases. Once cleaned, the drive will work fine.
If the motor spins slowly, it's getting cleaner, if it doesn't spin on it's own, you must disassemble the motor and clean the brushes and stator (round, copper thing, with multiple segments) with 800 grit sand paper.
As per a previous post, lock for any binds or drive kinks that may stop up the works. I've had this problem on several old cars, and it's just from lack of use in most cases. Once cleaned, the drive will work fine.
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11-02-2004, 08:36 PM
#8
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i had a similar problem with my front wipers not working - in my case it was the motor.i swapped it out with a good used one...not hard at all.
v-tach
1986.5--928
v-tach
1986.5--928
11-06-2004, 01:52 AM
#10
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Thread Starter
TONIGHT, FOR THE FIRST TIME IN A COUPLE YEARS, I HAVE WORKING WINSHIELD WIPERS! I CAN ACTUALLY DRIVE IT ON SOMETHING OTHER THAN A PERFECTLY SUNNY DAY!
Thanks to everyone for the suggestions! Doc, you were right about it being an oxidized motor. I had to pull it apart and clean it thoroughly. The magnets and stator were very rusty. And boy was it a pain getting it back into the car! I will try to write a recap later with some tips as reference for other novices.
Thanks to everyone for the suggestions! Doc, you were right about it being an oxidized motor. I had to pull it apart and clean it thoroughly. The magnets and stator were very rusty. And boy was it a pain getting it back into the car! I will try to write a recap later with some tips as reference for other novices.
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mgb63capri73 (08-07-2022)
11-06-2004, 08:19 PM
#11
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Thread Starter
One last post of tips for anyone else who comes across this thread looking for help on non-working wipers. Please note I'm just a novice and this is what worked for me. It's definitely not professional advice.
First, regardless of what the manual (or others) tell you, it is very tough to remove the motor and wiper assembly from the car. The picture in the factory manual showing someone pulling and turning it out with one hand is a cruel mockery of reality. On my 1986.5, I would have had to remove the hood to put it back in easily. As it was, I really had to force it in.
Because of this do everything you can to test for other problems *before* you remove the motor & assembly. Test to see that the motor is getting power. There are very small numbers on both the male and female electrical connectors (numbered 1-6). 6 is ground. With the wipers on -- you can put your probes on 1 & 6 or 4 & 6 and look for the 12VDC.
Also, check the fuse, and maybe relay, before pulling the motor & assembly.
Look to see if the assembly is bound up and/or just needs some lubrication to get going.
Look to see if your wiper arms weren't tight. Did they slip and are they now burying themselves into the trim at the bottom of the winshield, thus appearing not to work? (I did this when putting the arms back on prior to alignment.) When realigned (i.e. moved up the winshield) they'll work fine.
If you determine that odds are the motor is bad, then pull it. Like I said, it was a pain for me. You'll need to loosen the nuts holding the crank drive arm ends onto the "hood." (These are the nuts under the wiper arm caps.) The manual says you need a flat wrench. Since I have no flat wrenches, I was able to remove them by very carefully using hog nosed pliers. This requires extreme care not to damage the paint in that area.
If you're going to clean the motor then remove the wiper assembly from the motor. There's the one central nut and three other screws. Good luck if your screws are anything like mine. Even with lubricant, time and good screwdrivers I couldn't budge them. I ended up using a rotary tool to cut two straight edges on each screw and then grabbed them with a wrench. (Side note: why didn't Porsche use screws with hex nut heads here instead of round screws?)
When separated, do not remove the plate that covers the gears that transfer the motor rotation to the wiper assembly. (This is the silver part of the motor.) There is nothing to be gained from it and there are electrical contacts and grease paths inside. No reason to do it.
To open the motor for cleaning, note the bottom case is black and the top is silver. That's where it splits open. Remove the two screws. Then note that there are two retaining clips on the sides that pass through the silver and black parts. That may not be readily obvious if yours, like mine, is covered in a sealant goop. I pried for a while before realizing how they were held together. (Doh!) Scrape the goop off and then just pull the retaining clips outward. Then the motor can then be pulled open. The black case has two magnets inside that may need cleaning. The silver end will be attached to the brushes and stator (coil) elements. I used a wire brush wheel (on a grinder) to clean the stator elements. I didn't see an easy way to clean the brushes and they looked pretty clean, so I just sprayed them with some WD-40. I also sprayed some inside the black case and wiped a small amount on the outside of the stator elements to hopefully slow down future rusting. When reassembling I used a small tube of gasket sealer (non-hardening) to fill the openings around the side retaining clips and hopefully slow down the re-entry of moisture into the motor.
Putting it back in is tough but straightforward. Just make sure you have all of the necessary wires out of the way so you don't accidently trap something (like the female electrical connector) behind the motor when you finally manage to get the assembly in place. If you find out you have to take it out again after struggling to get it back in, you will be spitting nails. (I actually didn't do this. Really.)
That's about it. Hope it saves someone else some trouble.
First, regardless of what the manual (or others) tell you, it is very tough to remove the motor and wiper assembly from the car. The picture in the factory manual showing someone pulling and turning it out with one hand is a cruel mockery of reality. On my 1986.5, I would have had to remove the hood to put it back in easily. As it was, I really had to force it in.
Because of this do everything you can to test for other problems *before* you remove the motor & assembly. Test to see that the motor is getting power. There are very small numbers on both the male and female electrical connectors (numbered 1-6). 6 is ground. With the wipers on -- you can put your probes on 1 & 6 or 4 & 6 and look for the 12VDC.
Also, check the fuse, and maybe relay, before pulling the motor & assembly.
Look to see if the assembly is bound up and/or just needs some lubrication to get going.
Look to see if your wiper arms weren't tight. Did they slip and are they now burying themselves into the trim at the bottom of the winshield, thus appearing not to work? (I did this when putting the arms back on prior to alignment.) When realigned (i.e. moved up the winshield) they'll work fine.
If you determine that odds are the motor is bad, then pull it. Like I said, it was a pain for me. You'll need to loosen the nuts holding the crank drive arm ends onto the "hood." (These are the nuts under the wiper arm caps.) The manual says you need a flat wrench. Since I have no flat wrenches, I was able to remove them by very carefully using hog nosed pliers. This requires extreme care not to damage the paint in that area.
If you're going to clean the motor then remove the wiper assembly from the motor. There's the one central nut and three other screws. Good luck if your screws are anything like mine. Even with lubricant, time and good screwdrivers I couldn't budge them. I ended up using a rotary tool to cut two straight edges on each screw and then grabbed them with a wrench. (Side note: why didn't Porsche use screws with hex nut heads here instead of round screws?)
When separated, do not remove the plate that covers the gears that transfer the motor rotation to the wiper assembly. (This is the silver part of the motor.) There is nothing to be gained from it and there are electrical contacts and grease paths inside. No reason to do it.
To open the motor for cleaning, note the bottom case is black and the top is silver. That's where it splits open. Remove the two screws. Then note that there are two retaining clips on the sides that pass through the silver and black parts. That may not be readily obvious if yours, like mine, is covered in a sealant goop. I pried for a while before realizing how they were held together. (Doh!) Scrape the goop off and then just pull the retaining clips outward. Then the motor can then be pulled open. The black case has two magnets inside that may need cleaning. The silver end will be attached to the brushes and stator (coil) elements. I used a wire brush wheel (on a grinder) to clean the stator elements. I didn't see an easy way to clean the brushes and they looked pretty clean, so I just sprayed them with some WD-40. I also sprayed some inside the black case and wiped a small amount on the outside of the stator elements to hopefully slow down future rusting. When reassembling I used a small tube of gasket sealer (non-hardening) to fill the openings around the side retaining clips and hopefully slow down the re-entry of moisture into the motor.
Putting it back in is tough but straightforward. Just make sure you have all of the necessary wires out of the way so you don't accidently trap something (like the female electrical connector) behind the motor when you finally manage to get the assembly in place. If you find out you have to take it out again after struggling to get it back in, you will be spitting nails. (I actually didn't do this. Really.)
That's about it. Hope it saves someone else some trouble.
11-06-2004, 09:12 PM
#13
Rennlist Member
Great writeup! 
FWIW, removing the motor from my OB was a piece of cake... I removed the crank and the hoseclamp, then the three nuts where the shaft comes through, and I had to remove one bolt on the mounting bracket, way down at the bottom right of this pic(hidden).
I only removed it to get a better angle at the expansion valve. Took maybe 5 minutes to pull it. YMMV
FWIW, removing the motor from my OB was a piece of cake... I removed the crank and the hoseclamp, then the three nuts where the shaft comes through, and I had to remove one bolt on the mounting bracket, way down at the bottom right of this pic(hidden).
I only removed it to get a better angle at the expansion valve. Took maybe 5 minutes to pull it. YMMV
11-06-2004, 10:55 PM
#14
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i have a 1986.5 and im not a mechanic - changed my wiper motor fairly easy the only tricky part i thought was getting the wiper arms off the motor.
regards
v-tach
regards
v-tach
11-06-2004, 11:43 PM
#15
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Thread Starter
Sharkskin & V-tach,
I think a lot of my problems arose because I couldn't get the motor off the wiper assembly while still under the hood, so I had to remove the entire assembly so I could then remove the motor on the workbench.
Removing the motor alone wouldn't have been hard if the three screws weren't stuck so bad. Removing the entire wiper arm assembly and re-installing the wiper arm assembly was what gave me such trouble. Re-installing the motor (by itself after the arm assembly) was pretty easy.
Of course, maybe there's an easier way to get the arm assembly out and I'm a dummkopf. Wouldn't be the first time.
I think a lot of my problems arose because I couldn't get the motor off the wiper assembly while still under the hood, so I had to remove the entire assembly so I could then remove the motor on the workbench.
Removing the motor alone wouldn't have been hard if the three screws weren't stuck so bad. Removing the entire wiper arm assembly and re-installing the wiper arm assembly was what gave me such trouble. Re-installing the motor (by itself after the arm assembly) was pretty easy.
Of course, maybe there's an easier way to get the arm assembly out and I'm a dummkopf. Wouldn't be the first time.