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Smoove1010
 
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87 Carrera Backwards Intermittent Wiper Puzzle

It took some doing (topic for another post) but this weekend I got my wipers to work and park properly! Except, that is, the intermittent wiper function, which never worked, and is still not working.

Today I discovered why: The intermittent wiper potentiometer was disconnected and the leads taped off by a PO. "Aha," said I as I reconnected the three leads only to find after doing so that when re-connected, the potentiometer works exactly backwards! Clearly the disconnection was the PO's way of "fixing" the problem.

So, as it stands, when the knob is turned counter-clockwise past the detent, instead of being off, the wiper motor runs continuously; when turned clockwise, instead of wiping at progressively increasing intervals it instead runs at intervals that are progressively further apart, though it never totally stops.

If something is wired backwards, what could it be? I've searched the forum, checked diagrams, looks like all the wiring is right.

In keeping with this theme, here's the question posed in the reverse: If you wanted to wire your intermittent wiper control knob to work exactly the reverse of how it's intended, how would you do it?

Thanks in advance for any and all wisdom. Please help me solve this backwards puzzle!
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1987 3.2 911 Cabriolet
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Old 03-05-2018, 07:08 PM
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Old 03-05-2018, 07:20 PM
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Quote:
Originally Posted by 540964 View Post
Yes, thatís normal operation. Mine is the opposite. With the knob turned all the way left the wipers run continuously; when the knob is turned to the right the wipers work intermittently - the further itís turned right the further apart the intervals become (though they never completely stop.)

The switch case appears as though it may have been opened at one point - canít be sure - could the switch have been re-wired internally?
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Old 03-06-2018, 03:43 AM
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scumbag
 
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the way i'm reading this article is such.

full anti-clockwise, intermittent off
over the detent, intermittent on...and the pause between wipes increases the further clockwise you turn.

OP, is this not what your car is doing?
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Old 03-06-2018, 05:37 AM
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Here is the schematic if you want to check the wiring.
The potentiometer sb:
Pot term Wire
15 - RED / WHT
15b Ė BLK
15a Ė RED / YLW

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'87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip
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Old 03-06-2018, 07:53 AM
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Quote:
Originally Posted by Smoove1010 View Post
It took some doing (topic for another post) but this weekend I got my wipers to work and park properly! Except, that is, the intermittent wiper function, which never worked, and is still not working.

Today I discovered why: The intermittent wiper potentiometer was disconnected and the leads taped off by a PO. "Aha," said I as I reconnected the three leads only to find after doing so that when re-connected, the potentiometer works exactly backwards! Clearly the disconnection was the PO's way of "fixing" the problem.

So, as it stands, when the knob is turned counter-clockwise past the detent, instead of being off, the wiper motor runs continuously; when turned clockwise, instead of wiping at progressively increasing intervals it instead runs at intervals that are progressively further apart, though it never totally stops.

If something is wired backwards, what could it be? I've searched the forum, checked diagrams, looks like all the wiring is right.

In keeping with this theme, here's the question posed in the reverse: If you wanted to wire your intermittent wiper control knob to work exactly the reverse of how it's intended, how would you do it?

Thanks in advance for any and all wisdom. Please help me solve this backwards puzzle!
Smoove,
I think you might have a "ground loop" problem in your wiring.
I had a very similar problem years ago. Fixed it by cleaning all the
wire lugs in the battery ground wire stack where it bolts to the body
just to the right of the battery. It's worth a try. Here's my post from back then:

Pull off the ground connectors on the ground stud located on the inside of the left front of the hood right by the battery. There's a bunch of brass connecters there. Clean each one with emory paper and reinstall. Bet your problem disappears!
I had the weirdest problem ever on my '80SC, some times when I honked the horn or used the blinkers, the wipers would take a swipe, HUH! Then when at night I turned on the headlights, the wipers would turn on and stay on! Checked everything I could think of, and in my checking of the wiring diagrams I noticed the wiper intermittant relay had a voltage path running thru the wiper switch to the washer motor. I pulled off the wires on the washer motor with the headlights on, and the problem disappeared! Got out my Hi Tech Techtronix meter and "read" ground connection to the washer motor. When I turned on the headlights I read 1-2v on the ground connection! The small voltage was running thru the washer motor windings and was apparently enough to go thru the wiring and "pick" the intemittant relay!
Cleaned all the afore mentioned ground connectors and Voila! problem fixed.
Ground loops can do incredible and amazing things!
___
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Long gone but still miss them all:
'77 911 Targa, '72 BMW 3.0CS Coupe(finest car I ever had!)
'71 911T Coupe White, '70 911T Coupe Blue
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Old 03-06-2018, 09:15 AM
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Thanks for the response and the diagram.

I've got a pal who's an electrical guru looking at this schematic right now to see if he can reverse-engineer making it work backwards. I'll work on that ground-loop suggestion as well.

Thanks and keep those troubleshooting ideas coming!

GK
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Old 03-06-2018, 11:35 AM
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Mystery mostly solved! Problem caused by bad garage lighting: I mis-read the red/yellow-striped wire vs. the red/white-striped wire and reversed those connections on the potentiometer, hence there was always voltage being fed to the black wire (terminal 15b.) Once I swapped those connections the intermittent function works properly. I did learn that the pot works the opposite of what I expected, i.e., the intermittent speed starts off high and decreases as the knob is turned clockwise.

Turns out my wiper dysfunction was due to two things:
1) The spade connector for the green lead was pushed down into the the plastic plug on the wiper motor - fixing this restored the park function and wiper low speed;
2) Discovering that the potentiometer was disconnected, reconnecting it, and reconnecting it again properly fixed the intermittent function. The only mystery left - why was the pot disconnected and taped off? Only the PO knows...

As my mom always says, "it's usually something simple..." Next challenge: figure out why the windshield washer isn't working...

Thanks forum friends!
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Old 03-07-2018, 04:48 AM
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Great job tracking down the problem!

For the windshield washer problem, do a simple test of the pump motor with wire leads directly from the battery. I wouldn't be surprised at all if the pump motor is seized. The VDO pumps are good pumps (they can pump a lot of fluid really fast and can run a long time w/out overheating) but they tend to get seized with age. Not to mention the crimp fittings on the hoses tend to leak a lot.

You may wonder why would anyone know or care if the washer pump can run a long time and not overheat? Only reason I know that is because one of Grady Clay's cool inventions was the "Rubbermaid Solution" where he used a collapsible camping water jug, a Rubbermaid tub, some bungee cords, a series of resistors to throttle down the pump speed and a windshield washer nozzle to spray the engine cooling fan with a shot of water mist. The water mist provides a significant amount of added cooling to the engine

Water vapor cooled 911 - the Rubbermaid Solution
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Old 03-07-2018, 01:42 PM
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And if it turns out you need a windshield washer pump I have one that turns out wasnít needed that you can have cheap...send me a pm.
Old 03-07-2018, 01:53 PM
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Cool - congrats and thanks for letting us know.
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'87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip
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Old 03-07-2018, 06:37 PM
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Smoove1010
 
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Quote:
Originally Posted by KTL View Post
Great job tracking down the problem!

For the windshield washer problem, do a simple test of the pump motor with wire leads directly from the battery. I wouldn't be surprised at all if the pump motor is seized. (snip)

You may wonder why would anyone know or care if the washer pump can run a long time and not overheat? Only reason I know that is because one of Grady Clay's cool inventions was the "Rubbermaid Solution"...

Water vapor cooled 911 - the Rubbermaid Solution
Hey KTL - I loved reading that thread of Grady Clay's - I'm a big fan of low-tech solutions like that and an even bigger fan of the geniuses that dream them up. I've spent hours reading Grady's posts - they could be assembled into a great book.

I had already done what you suggested when I saw your post: The washer motor when jumpered wouldn't turn. I parted the pump section from the motor section and the motor worked beautifully while the impeller was indeed seized, but that was readily solved by spraying some WD40 in the ports and working the impeller back and forth.

There was a second part to this fix though: A plastic plug with a brown and a white/green wire was attached to the ww pump while the correct yellow and brown wires were taped off and set aside. I have no idea what that other mis-applied plug is for. I also noted that my car has a headlight washer relay though I don't have headlight washers!

With the pump un-seized and the correct wires in place, I began testing my re-install of the wiper motor to check for the proper "park" position when - more joy - fluid squirted from the washer nozzles onto the windshield! I had assumed that the lines or tank would be clogged or fouled but it looks like I just need to add some blue stuff to the tank and I'm ready to go!

Next up: Figure out why my fog lights don't come on (whether the headlights are on or off.) Might as well do this now before re-installing the air handler just in case a PO disco'd something else...
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Old 03-08-2018, 12:58 PM
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Quote:
Originally Posted by Ctopher View Post
And if it turns out you need a windshield washer pump I have one that turns out wasnít needed that you can have cheap...send me a pm.
I got mine running again but I don't yet know if it leaks. If so I may give you a pm. Thanks!

GK
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Old 03-08-2018, 12:58 PM
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Grady's stuff is great reading indeed for all of us. Reading his stuff is like reading a professor's summary of an issue from both a textbook/technical side as well as the real life in-practice side. What a wealth of knowledge that man was. RIP always Grady!

Great to hear you got the pump going. Impressively simple, aren't they?

Some of the wiring is placed in cars even though they weren't equipped with certain things. Your car may also have some wiring in there for the high intensity windshield washer system which is basically another small pump and reservoir for extra windshield cleaning.

High Intensity Windshield Washer Tank

I just saw yesterday someone pointed out that the Euro side marker wiring harnesses were installed in all cars. So it doesn't surprise me if you've got stuff in the car for headlight squirters that aren't present. Crazy!

Fog lights are pretty straightforward. There's some wires in the trunk area at the front wall of the chassis. They use the weird clear plastic connectors. There's also a relay for the fog lights too. How funny/ridiculous is it that the fog lights have a relay but the primary headlights do not??????

While you're messing with the fog lights, maybe take a look at the headlights too and see if this interests you. One thing I find weird is the running lights can be on w/out the key on but the headlights are not. This can cause a dead battery, especially if you accidentally bump the turn signal switch to an "ON" position. These threads show how you can rewire the parking light activation

Running/Park Lights On All the Time, and Off with Key

LED Brake Lights
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Old 03-08-2018, 01:20 PM
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Quote:
Originally Posted by KTL View Post
While you're messing with the fog lights, maybe take a look at the headlights too and see if this interests you. One thing I find weird is the running lights can be on w/out the key on but the headlights are not. This can cause a dead battery, especially if you accidentally bump the turn signal switch to an "ON" position. These threads show how you can rewire the parking light activation
The right or left running light staying on with key off and turn signal
activated are a very common thing in European cars. It's meant to
provide a right or left warning lite to oncoming traffic when parking alongside narrow streets. If you are only in the restaurant or beir stube for a couple of hours it shouldn't run your battery down. LOL
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'80SC Widebody 3.6 transplant Anthracite "The Rocket"
Long gone but still miss them all:
'77 911 Targa, '72 BMW 3.0CS Coupe(finest car I ever had!)
'71 911T Coupe White, '70 911T Coupe Blue
'68 911 Coupe Orange, '68 911L Soft Window Targa
Old 03-08-2018, 01:54 PM
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Yah no German has EVER hung out in a pub for more than a few hours and would NEVER drink & drive?

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Old 03-08-2018, 02:11 PM
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Quote:
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Yah no German has EVER hung out in a pub for more than a few hours and would NEVER drink & drive?

HaHa! Maybe it's an anti DWI thing, if you stay way too long in the bar
it could leave you with a dead battery and prevent drunk driving. LOL
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'80SC Widebody 3.6 transplant Anthracite "The Rocket"
Long gone but still miss them all:
'77 911 Targa, '72 BMW 3.0CS Coupe(finest car I ever had!)
'71 911T Coupe White, '70 911T Coupe Blue
'68 911 Coupe Orange, '68 911L Soft Window Targa

Last edited by uwanna; 03-08-2018 at 02:50 PM..
Old 03-08-2018, 02:16 PM
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Quote:
Originally Posted by KTL View Post
-snip-
Some of the wiring is placed in cars even though they weren't equipped with certain things.
-snip -

-snip-
Fog lights are pretty straightforward. There's some wires in the trunk area at the front wall of the chassis. They use the weird clear plastic connectors. There's also a relay for the fog lights too. How funny/ridiculous is it that the fog lights have a relay but the primary headlights do not??????
-snip-
Fog lights are fixed! Went through the basics, discovered almost by accident that the fog lights would work when the high-beams were on but not the low beams (that opposite theme again) and determined that there were wires switched around on the fog light switch itself. So glad I decided not to re-install the air handler before I fixed this!

Discovered another bundle of 4 wires up near the fog light switch, determined that those were for the rear fog lights - another feature that's not on this car, so I do believe you are right about cars all getting the same harness regardless of the option package.

Now that I'm putting the car back together I found that the clips that hold the center vent in the dash are all broken off - topic for another post...

Thanks for the input!
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Old 03-10-2018, 12:26 PM
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