I'm hoping someone with some electrical background can help me diagnosing what's what with the intermittent wiper circuit on an 84 944. The FSM wiring diagram (page 97-43) shows the circuit with all of the connections between the wiper switch, wiper motor and the intermittent relay. Confusion sets in on the operation of the relay. Terminals S1 and 31 are supposed to power the transistor (or whatever it is) and it appears that 31 goes to ground while S1 should get 12V when the wiper switch up pushed down (the 3rd position - in opposite direction from slow/fast). It's pretty clear that 53S and 53M complete the homing circuit and terminal 15 supplies the 12V to the wiper motor. The switch diagram seems to indicate that when the 3rd position is selected, switch terminal S1 should connect to 53a to receive 12V to power the transistor. However, after having pulled out the switch out and under close examination with a VOM, I find that the only way S1 will connect to 53a (and receive 12V) is when the switch is pulled back which also activates the windshield washer circuit. Now it doesn't make much sense that you could only get intermittent wiper action while running the washer (and having to keep pulling the stalk). After closely examining the switch contacts, I am reasonably sure that nothing is wrong with it and all other connections check out properly (i.e. low and high speed wipers). I have to wonder: does anyone out there with an early 944 actually have working intermittent wipers? I can scan in this part of the circuit if nedded.

 

diagram....

 

Do you mind if I take a SWAG at this one? The transistor has power only when the stalk is pulled back <to wash the windshield when you get something on it> Is this right?

FWIW: I think it may be a bad transistor...silicone can break down over the years. Here's a cool article I found explaining stuff: http://www.repairfaq.org/sam/semitest.htm
I was looking up stuff to remember my component electronics training. It's been a while and it left my brain :-). But my gut says it is your transistor. I'll leave out the theorizing about biasing currents and such ;-).

 

I agree the transistor is most likely bad Alexis but I'm still puzzled as to how it would receive power independent of the washer circuit. What I didn't mention in my first post is that I intend to hook up a wiper delay kit (w/variable delay) that I bought from a place in Canada for only ~$20 incl. shipping. (https://store.qkits.com/) I was hoping to hook it up as a replacement for the orignal ($$) relay and so this is why I'm digging into the details. I had planned to plug spade connectors into the vacated relay's socket and wire it up like that. This is when I found this apparent error in the intermittent circuit (as far as I'm concerned). But it was easy enough to hook it up since terminal 15 on the relay socket supplies the 12V when the key is on and 53S and 53M are correct for the homing circuit. A ground wire to chassis and it works fine. Luckily it has it's own on/off switch so I don't have to use the wiper stalk. I'm still curious if anyone has the original relay in there that works properly.

 

bump.

 

That transistor is used to drive the coil of the relay. This cuts down on the shock that the switch in the wiper arm has to endure when you choose an intermittent wipe. If the relay isn't closing, then either the relay is bad or the transistor is bad.

 

Mike C.,
Unfortunately I don't have an answer but I do have a question.
I just picked up an '84 and am puzzled as to the operation of the wipers. On mine if you push the handle all the way down towards the ignition switch, I get intermitent operation. Go up one and you get low speed. Go up one more and you still get low speed...no change. Go all the way up and it stops????
With the handle all the way up it partially blocks the view of the tach. I can't imagine that is the correct off position.
Can you help clarify this?
Thanks!

 

Mike,

From the factory the intermittent wiper can operate three ways.
1. Push up lightly and this triggers it to wipe once.
2. Push into down position and goes into intermittent mode. I think every six seconds.
3. Pull back on the wiper stalk to get the washers, you trigger the relay to intermittent wipe for three swipes and spray. This gives the washer time to spray.

I have a somewhat similar problem with my early 85.
After I swapped my tach around, the wiper fuse kept shorting out everytime I hit the intermittent wipe, either all the way down or pulled back. I pulled the whole assembly apart and hooked up the VOM and the switch turned out to be bad. I ordered a new brown wiper stalk from PP and an original parts box arrived with a Genuine Porsche part in it. I dropped this in (along with a new relay) and now all that works is #3 (the three swipe wipe) or a slight push up will wipe once. However, if I put the stalk all the way down to #2 (intermittent wipe), it stays on all the time. Got me. I have to look at the diagram you posted and get after it this winter.

Thompson
1985 944.1 Club Sport targa
1995 S6

 

Aribop, The switch should have 4 positions, Off, low, hi, intermittent. Low is one notch up from off, high is 2 notches up from off. The switch should stop here (you should not be able to move it up to a third position). If you push it down from off, this is imtermittent. If you are able to move the switch to get more than 4 positions then I would say there is a problem with it. It sounds like the spring loaded clicker is screwed up and unfortunately, there doesn't seem to be any way short of grinding to take this thing apart to fix it. One pin holds it all together that is mushroomed over.

 

My First call- Transistor went south. replace it.

IIRC- Ohm's law electricity seeks the least path of resistance.

FWIW- Make sure your grounds are clean and do a continuity check before replacing anything.

 

Mike is right with the 4 pos. switch arrangement. I too am having problems with my intermit wipers. All positions work as stated above except the lower position for intermit. In this position I get a slow wipe. I would guess the intermit. relay would be the culprit here, but what puzzles me is when I return the stalk back to the off (one up from lowest) it stops arms immed. and they don't return to the lower prtion of windshield. I basicaly have to time the movement of the wiper arms with turning off the switch to stop the wiper arms in the off position.

This is a pain if you are in traffic and there is a mist or light sprinkle.

Any ideas? Could it be a same relay? or maybe the motor itself?

 

Rain - X. I have had no wiper washers since I GOT the 924s- never needed them.

If only one dentent wont work it's an internal switch or a relay- system wont work as a whole- check your grounds first before digging in on the electricals.

HTH.

 

Hi Dean,

Terminals 53M and 53S on the intermittent relay connect the homing switch (in the wiper motor). When the intermittent relay is in the off position, 53M and 53S are connected. If you pull out the relay or it has bad contacts for these connections, your wipers will not home (they will stop wherever you turn them off). To test this, you can pull the relay and then jumper these connections on the relay socket (the terminal ID's are shown on the bottom of the relay).

 

I'm replacing the intermittent relay with this nifty little board which also provides delay adjust 3 - 30 seconds. Since I don't smoke, I thought the ash tray would be a good place to hide it.

 

Thanks Mike

Thats a nifty idea for your intermit. delay. Very cool.

Let us all know how it works out.