I’m troubleshooting my windshield washer circuit and I’m stuck:

1)      The wipers work but the washer motor has not run since I got the car ~5 years ago.

2)      Voltage measured between the two wires when unplugged from the washer motor reads 3.8V when the washer button is pressed.

3)     At individual wires I’m getting around 12V to relative to ground (11.97V and 12.31V) when the washer button is NOT pressed.

4)      On one washer motor wire I’m getting around -0.56V to ground and +3.2V to ground on the other wire when the washer button IS pressed.

I’m assuming that there should be +12V going to each contact when the sprayer is not used and then drops to 0 volts on ONE contact when the sprayer is used. However, when I press the switch, voltage difference between the two wires is only 3.65V which is not enough to operate the pump.

I’m finding the wiring diagram a little confusing so can anyone offer me a starting point on my trouble shooting.

BTW: I was at the Pittsburgh Vintage Grand Prix last weekend which had 4 Z's in their > 2 L sports car class. It was a lot of fun to watch and to check out the Zs and other cars in the car show lot.

Possibly the motor windings have deteriorated and not passing on enough current.

2 hours ago, Yarb said:

Possibly the motor windings have deteriorated and not passing on enough current.

I have a new sprayer motor installed so no. Also, all the voltages I provided were read from the two wires that power the motor with the motor disconnected from them.

Check the voltage with a 12v bulb in place of the pump. then you know if the new pump is good. Put a voltmeter over the bulb's contacts and if the voltage is to low say 5v or so than you need to replace or clean your switch.

use a 12v 23 to 60 watt or something like that.. for the bulb. (It's possible that a 55-60 watt bulb will draw so much current through your switch it "cleans" the contacts.. haha 🙂 )

Motor is prob rust/shorted out, excessive current draw, corroded wires, etc... Those motors are not well sealed from the pump. Clean the bullet connectors and get a test lamp like a tail light bulb. if that light up then your supply is fine, next apply voltage from a 9v battery, to the motor, that should spin it. if not then forsure the motor is bad.

I'll need to figure out how to get to the button on the end of the wiper stalk to clean up its contacts. I might need to table this issue until fall when I attack other issues with the dashboard. 

As for the sprayer motor, it is new and will spray when I power it directly from the battery. 

32 minutes ago, Jeff Berk said:

I'll need to figure out how to get to the button on the end of the wiper stalk to clean up its contacts. I might need to table this issue until fall when I attack other issues with the dashboard. 

As for the sprayer motor, it is new and will spray when I power it directly from the battery. 

You don't need to remove the button. The switch contacts are at the other end of the switch.

Here's a short video showing the contacts.

You'll need to get between the copper arms and tabs to clean those surfaces.

There are 3 screws that hold the parts together. Be careful removing the screws on the side because there are small plastic washers that insulate the circuit. Once you have the contacts removed, you can polish them with a dremel w/wire brush, emery paper, or dip them in vinegar for a short time.

Edited July 27, 20231 yr by SteveJ

By the way, create a signature and put the year of your car(s) in it. There can be other diagnostic information developed if we know the year. 

At least put the year of your Z in this thread.

One more clarification, last night's instructions for disassembly were for a 77-78 switch. This is why the year is important. The 73-76 has four screws on the side that need to be removed. I haven't tried to dig up an earlier switch to look at it.

Edited July 28, 20231 yr by SteveJ

I think it should be possible to service the washer circuit contacts by removing only the screw that holds the contact spring blades in place. Open the wiring harness support bracket to allow movement of the wiring before loosening the screw. Several tiny parts in this area, be careful not to lose anything - do the work over a soft towel to avoid runaway bits! Going this route avoids a much more complex disassembly involving the switches.

I didn't realize there was a switch to view signatures let alone a way of generating one. I've written a short sig for now.

3 hours ago, jfa.series1 said:

I think it should be possible to service the washer circuit contacts by removing only the screw that holds the contact spring blades in place. Open the wiring harness support bracket to allow movement of the wiring before loosening the screw. Several tiny parts in this area, be careful not to lose anything - do the work over a soft towel to avoid runaway bits! Going this route avoids a much more complex disassembly involving the switches.

 

Exactly what I was trying to say.

By the way, Jim, the switch I have handy this is of a similar vintage to the one in your photo has a plastic washer where yours has a metal washer.