2 hours ago, SteveJ said:

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.

Actually, that is a discolored plastic insulating washer.

5 minutes ago, jfa.series1 said:

Actually, that is a discolored plastic insulating washer.

Okay, I took a closer look. At first glance it looked like tarnished copper.

I took the switch off and cleaned up the contacts with vf sand paper and contact cleaner spray. 

I'm still getting the voltage readings: ~12 volts on both connections when the button is NOT pressed, and ~3 volt difference between the two connections with the button pressed. If instead, one of the two contacts dropped to zero and the other stayed at 12 volts, it would work.

One more question, should the wipers start wiping when I press the sprayer button because they don't. 

This is not a major issue since I don't intend to drive my car in the winter but its just one of those things that's on my list of things to fix.

Edited July 28, 20231 yr by Jeff Berk

Looking at the switch design suggests each of the contact blades is completing an independent circuit - one for power and one for ground. I recommend you run a continuity check for each circuit to verify each is working correctly. If so, that will take the switch out of the problem. As to the wiper question, the answer is no - the wipers do not come on when the washer is activated.

14 hours ago, jfa.series1 said:

Looking at the switch design suggests each of the contact blades is completing an independent circuit - one for power and one for ground. I recommend you run a continuity check for each circuit to verify each is working correctly. If so, that will take the switch out of the problem. As to the wiper question, the answer is no - the wipers do not come on when the washer is activated.

Looking at BE-64 of the FSM and how the switch's stationary contacts are mounted, one of the circuits is a ground. I might have to connect the battery and turn the ignition on and probe around with a multimeter to figure out what's going on.

I'm still confused as to why there is 12v going to both contacts on the sprayer when the sprayer button is not pressed. It seems like one contact should be a ground and the other only showing 12v when pressed. 

 

 

Edited July 29, 20231 yr by Jeff Berk

Actually, from 73 on, the wipers should single swipe with the washer. (If you hold down on the button, they should keep swiping.) It's probably the same with the 70-72, but I'm not sure if that's a function of wiper amplifier.

While there looks to be 9 wires going to the amplifier, there are only 7 in reality as there is only one 12VDC+ (B terminal) and one ground (E terminal) on the amplifier. 

So as the notes say in the picture, when you press on the washer button, you are completing the ground leg on the washer motor. At the same time, you are grounding the W terminal on the amplifier and providing 12VDC+ on the I terminal. That should get the wiper motor to swipe.

I attached a PDF where I highlighted the wires going to the I (Blue), B (Red), and W (Green) circuits.

Now for the final testing.

The car should be off for this test. Plug in the combo switch and unplug the LW wire from the washer motor. Have someone hold the washer button. While the button is pushed in, measure resistance to ground from the LW wire at the wiper motor. It should be less than 1 ohm. (Note the scale if you have an autoranging meter.)

Now for the more PITA test. With the car still off, get up to the relay panel on the passenger kickpanel. Unplug both connectors on the amplifier. Have someone hold the washer button while you measure continuity between the LR wire on one connector to the blue wire on the other connector. That should be less than 1 ohm.

1974 Wiper Motor Circuit.pdf

I stand corrected on the question of the wiper activating with the washer. Sorry for the bad info. 1973 introduced the intermittant wiper function so that could make a logical tie-in to the washer circuit.

 

4 hours ago, jfa.series1 said:

I stand corrected on the question of the wiper activating with the washer. Sorry for the bad info. 1973 introduced the intermittant wiper function so that could make a logical tie-in to the washer circuit.

 

I went back and confirmed. The wiper function isn't on the 70-72. The nice thing is that you got me thinking more about how the wiper switch works since I'm trying to adapt the Sentra wiper amplifier to the 73-78.

With the combo switch plugged in and the LW at the washer unplugged, I get 0.7 ohms when the switch is pressed.

With the two connectors on the amplifier unplugged, I get 0.9 ohms between the two washer pump wires when the switch is pressed. 

Okay, so if you haven't cleaned up the contacts, do so and try it again. The good news is that there are no breaks in the wires, and the switch is functioning. 

I'll have to think of some more diagnostics later to verify what's working and not working.

I found a spare intermittent wiper relay in my parts bin but substituting it didn't correct the issue. 

I noticed that if I press and hold the washer button, the wiper will wipe a couple of times so it looks like the washer is charging the capacitors in the wiper relay. Also, if I hold it too long, I blow the 20 amp fuse.

I unplugged and cleaned the contacts for the wiper motor and all of the D-shaped color-coded connectors under the glove compartment. I used contact cleaner spray and a small-diameter nylon brush to clean the female and a small nylon brush wheel on a Dremel to clean the male contacts.  I've seemed to have picked up about a volt so that I'm getting 4.0 volts at the washer motor contact when the button is pressed.

I'm wondering if I should check resistance between wire segments or turn the power on and check voltage at various points?