WW Intermittent Failure - '81 Datsun 510

The Intermittent function on my '81 Datsun 510 windshield wipers has extended the delay time to infinity, and I don't want to wait that long - particularly when it is raining.   

Both the full-time low and high-speed settings still work, but the wipers usually won't 'home' properly when I cut them off without timing it right.  Heck, the car ain't but 22 years old - I haven't got all the good out of it yet! 

Can anyone help with the diagnosis?

this started happening in my 96 caravan a couple months ago, but it doesn't always happen.  Sometimes the intermittent will work just fine, other times it seems to have amind of its own.  Most of the time it'll do two wipes in a row, and then pause for however many seconds it's set for, then it'll do two more wipes in a row, etc....

One time if I turned them off while they were in the middle of a cycle, they would stop up on the windshield, you know like the way some cars will do it if you turn your car off before turning off your wipers.  But it did that while i was still driving and with the car still on.  So to get them to retract and stay out of my way I had to time it so that I turned them off when they were all the way at the bottom of their sweep.

I have no idea really what the problem is but i've heard of other caravan owners having similar "magical wipers" issues.  Not really sure what to suggest for your vehicle as it's so old i don't know what controls the intermittent function.

E -

I'm happy to report that I have found/fixed my problem.  But not a whole lot of thanks to 'AJAYZ AUTOMOTIVE WIRING DIAGRAMS AND ELECTRICAL SCHEMATICS'.  At least, not so far.  (Do a Google search for 'automotive wiring diagrams' or 'automobile wiring diagrams'.)

I bought a copy of the (supposed) wiring diagram for this 510 wagon for $8.00 (reasonable price), but the first 'copy' was a freakin' nightmare to try to read.  Absolutely terrible; couldn't make out half the wire colors and other descriptors, image blocks staggered and shifted (like I ended up), etc.

I raised Cain, and he/she/it later sent me a copy in 'Greyscale', which image-wise was far superior to the first one.  Only problem then was I soon determined neither diagram matched my cars' (plural) wiring harnesses.  Both images appeared to be from the same reference source but clearly not the same actual document.  The WW circuit didn't come close to what I had in both 510 SW's I (still) have.  Drive one and use the other for a rolling parts bin.

But, Hey, look on the bright side, I said  - at least it was a lot easier to trace the circuits I didn't have!

Now, to the problem.  I found the Intermittent amplifier under the hood by the relay clicking it (sometimes) made when Intermittent operation was selected.   I then gained access to the light/wiper switch (polite way to say I almost dismantled the steering column) & tried (by myself) to trace the wires and check voltages like a good tech would that wanted to learn something (but mostly to spite that bloody @#$% diagram).  Spent too much time running back & forth. 

Finally got aggravated & went to Plan B.  Took the Intermittent Amplifier PCBA out of the case, and found a  corroded, detached capacitor lead, so replaced the cap (I'm in electronics repair).  Put it back in, still didn't work.  I juiced up the 'parts bin' to make sure the Int function still worked on it (and it did), so got it off (in about a third the time for the first one).  Stuck it in - 'Lo and Behold!  Works like a champ!' 

I then compared the two PCBAs, and realized that the relay armature contact arm *button* was missing in the bad board.  I had previously checked continuity thru those contacts, and it measured good.  I've seen contact arms with a hole in the blade at the contact point for cooling, so didn't think anything odd on the first pass.  Live and learn.  There still may be another problem with the PCBA, but I ain't gonna cannibalize the working one to find out.  Not today, anyway.

Now, for your situation.  You didn't say whether the Intermittent action has *always* been for two cycles or not.  My belief is that most WW motors have either an internal 'return cycle' voltage contact surface that is not quite a full 360 degree circle, or a plastic cam-actuated set of contacts.  Once a wipe cycle has started, a contact button rides this surface (Case #1) or the 'In-cycle' contacts close (Case #2), and provides a parallel voltage path to (a) motor winding during the cycle. 

If the wiper switch is cut off midway thru a cycle, then this 'return cycle' voltage path remains engaged until the motor mechanism reaches the 'home' position, at which point the button has passed the end of the contact portion of the circle (or the cam opens the contacts) and thus no longer applies voltage to the winding; the motor stops.

My failure exhibited that same symptom, in addition to eventually never even kicking off the wipers when the Intermittent position was selected, yet the 'full-time' low and high-speed settings continued to function normally.  This is likely a safety issue since they are simply 'hard-wired' connections through the WW switch, and don't involve any fancy electronics.

There are several connections between the motor, the IA board and the WW switch that  interplay in this operation.  For timing delays, the Int Amp PCBA has circuitry that is controlled by the setting of the delay potentiometer (variable resistor) on the WW switch.  Some vehicles have a variable adjustment while others offer one or more fixed delay intervals.  The adjustment or setting of the 'pot' causes the circuit to decrease or increase the length of the trigger cycle to kick off the wipers.

I find it interesting that  you get two cycles out of an operation.  If your Intermittent operation is relay controlled (solid state or other), then the 'pick' signal must be held long enough for the 2nd cycle to begin before it drops, then the normal completion mode takes over (sounds reasonable anyway).

Based on my clearly extensive experience in these matters, I would surmise that the IA in your vehicle is the culprit rather than the WW switch or the motor.  Check your manual for the location of this item.  Perhaps Dodge was kind enough to make it a plugin deal rather than the hidden sidewall mounted rig like I have - and dislodging screws that have rusted peacefully for 20+ years.

Hopefully it isn't a WW switch problem or you might get a chance to remove the steering wheel (a one-piece combination light and WW switch - like mine).  At least the WW motor should be in a somewhat open area - maybe.

Plan A: Try to find someone (smaller than you) with a like make and model, and while they're not looking, swap the modules - just for a test, of course.  No need to unduly worry them with the details. 

Plan B: Call and find out the cost of a new module.  Then try to locate one (preferably two) at a Vehicle Retirement Centre (junkyard), armed beforehand with the knowledge of about what they should charge.  Go get one & plug it in onsite.  If it changes the symptoms (as in it works), Viola!  If not, go to Plan A.