Very Frustrated. Electrical experts required please.

DJB · 01-04-2003, 07:33 PM

I have been chasing an annoying problem on my 86 Cab with my wipers and washers for a few weeks.

Basically everytime I turn on the ignition, my windscreen washers squirt and the wipers wipe in intermittent mode.

I have checked out the column switch and replaced the very expensive intermittent wiper control unit - no joy.

I am now thinking that it may be either the windshield washer relay or the additional washer fluid switch. I am looking at the electrical diagram on page 970-89 of Bentley, but my limited electrical knowledge is not good enough to determine if a failure in one of these components would cause these symptoms.

I have disconnected the intermittent wiper control module as a temporary solution.

Any thoughts or assistance would be greatly welcomed. Also maybe could tell me if the washer relay is the same as any other in the car to enable me to perform a test.

Thanks

Speedy1 · Speedy1's Garage

OK this only from experience and possibly not related but I had a new 90 Chevy blazer that had almost the same problem when I turn ignition on the windshield wipers would swipe once. It turned out to be the control module. Voltage is supplied to this device every time the ignition is turned on I'd try a new or a borrowed control unit next.

Kevin Stewart · 01-04-2003, 08:51 PM

I have had relays get stuck in the past, try using a test light to check the relays, Kevin

jeff m · 01-04-2003, 09:56 PM

When something operates when it shouldn't it is very often a missing ground.
It's similar to the headlight that flashes dimly in sympathy with a turn signal.
Check on the diagram to see if they are on the same ground run. (ignition and washers)
Then get a length of wire with croc clips at both ends, one end to ground the other end to were you think the missing ground may be.
The ground wires are brown. Then switch on ignition till washers don't op.
Jeff

DJB · 01-05-2003, 03:32 AM

Thanks Guys,
Speedy - I have already replaced the control module with no joy.

Kevin - Dumb question but how do I know the state of the relay when I test it ???

Great idea Jeff will do this in the morning.

Thanks - Some new things to try.

john70t · 01-05-2003, 04:02 AM

Electrical circuits are quirky in that bad grounds will cause backfeeding (and activate) through another circuit to get back to that battery negative.
If it happens all the time, you are lucky in that it's not intermitent. Try putting extra jumpers to ground to see if that clears it up.

autobonrun · autobonrun's Garage

Quote:

Originally posted by DJB
I have been chasing an annoying problem on my 86 Cab with my wipers and washers for a few weeks.

Basically everytime I turn on the ignition, my windscreen washers squirt and the wipers wipe in intermittent mode.

I have checked out the column switch and replaced the very expensive intermittent wiper control unit - no joy.

I have disconnected the intermittent wiper control module as a temporary solution.

Any thoughts or assistance would be greatly welcomed. Also maybe could tell me if the washer relay is the same as any other in the car to enable me to perform a test.

Thanks

I'll start with the second question. To check relays and other components (eg. fans, etc.) I would get either a small 12v battery (or 2 six volt batteries and put in series). You'll need a bag of leads with alligator clips on each end. I find this setup is good to keep on my work bench for testing various electrical components regardless of whether its needed for this particular fix.

First, the relays in the tech books are shown in what's called shelf position. They are shown with no power applied to the relay. If you pull one of the relays in the front of your car( say the power window relay) and look on the bottom, the numbers coincide with those on the drawings. Typically 85 is plus and 86 is negative. If you apply 12 volts to these points, you'll hear and feel the relay pick up. Again using the power window relay as an example, the contact 30 to 87 show as normally open. So using a voltmeter, when you apply power to 85/86, you should see the
ohms between 30 and 87 go to zero. If the relay does not change state, or the contacts don't change resistance, the relay is bad. This could be a result of welded contacts or an open coil in the relay. I think the wiper relay is a different type but the principle is the same.

As to your specific problem, the only book I have is through 1983 so you'll have to check a couple things. My book shows the windshield washer circuit bypassing all the intermittent wiper circuitry and being direct connected to the windshield wiper switch contact 53c. See if your setup is the same. You did not say whether when you pulled the intermittent relay the washer motor still operated.

If so, since the intermittent circuit gets its power from the same
point as the washer, it appears that the 53c contact of the wiper switch is not opening up as it should. I know you say you checked it but make sure that power is being removed from 53c when the wiper switch is in the off position. If not, the problem is with this switch. Using a voltmeter, verify 12v is NOT on 53c when the switch is in the off position. This is the very first check you should make.

DJB · 01-07-2003, 01:45 AM

Thanks to all especially to Autobonrun for such a detailed answer.

The problem turned out to be the relay, thanks for the test procedure. All is now fixed for the cost of a relay.

You guys are the best.

Thanks

car911 · 01-07-2003, 08:56 AM

Quote:

Originally posted by DJB
Thanks to all especially to Autobonrun for such a detailed answer.

The problem turned out to be the relay, thanks for the test procedure. All is now fixed for the cost of a relay.

You guys are the best.

Thanks

Quick question. Which relay are you referring to? On my '84, the washer circuits are on a fuse and no relay is involved from what I can see.

car911 · 01-07-2003, 09:01 AM

Quote:

Originally posted by jeff m
When something operates when it shouldn't it is very often a missing ground.
It's similar to the headlight that flashes dimly in sympathy with a turn signal.
Check on the diagram to see if they are on the same ground run. (ignition and washers)
Then get a length of wire with croc clips at both ends, one end to ground the other end to were you think the missing ground may be.
The ground wires are brown. Then switch on ignition till washers don't op.
Jeff

I have a situation where my wipers turn on by themselves when the motor is running. Is it possible for a ground to go faulty only when the motor is running? Where would I look for such a fault? Appreciate any insights.

jeff m · 01-07-2003, 12:10 PM

It's possible but when you have a missing ground or intermittant ground the two "things" that are operating are "sharing" the voltage.
That's the reason the bulbs only glow dimly.
In your case the wiper moter takes a bit of "umph" to operate, so it is more likely to be a faulty switch. That's assuming the wiper moves at normal speed. Or Chaffed wiring behind switch.
Jeff