71 240Z High Beams Work Low Beams Don't

[Richie G]

@SteveJ My first attempt was to actually disconnect everything and test (but I did leave it connected to the stalk.  Testing the switch from the sodder points gave me 0L readings in all scenarios across all wires except the initial YG - YB which had a .0000 OHM reading for continuity in the off position.  When i saw that I thought i was doing it wrong so then connected it again to retest with above results.  I'm not an electrician, but wouldn't that be expected if the harness is open and disconnected?  I would think I should be checking from the harness side so there is a completed circuit when testing in various conditions.  Also, since I know the switch works in low, when I was getting all those 0L readings in the low setting when unplugged I really thought I was doing it wrong.

 

 

[SteveJ]

If the black wire is either OL or 47+ ohms to the other wires, that is a problem. The circuit operates by grounding the YG (on the switch) wire in low and high. That is for the relay in the motor to spin it in the correct direction. (The opposite direction is for the park function.)

Then, the low speed wire (YB on the switch) is grounded in low. It should have low resistance to the black wire. (I would want it to be as close to zero as possible.)

Next, the high speed wire (RL on the switch) is grounded in high. Again, it should have low resistance to the black wire.

The reason for disconnecting the switch is to prevent confounding results. I have not tested a wiper motor separate from the car, so I didn't know if it could affect measurements.

I have a couple of wiper switches that do not appear to the functioning properly. I may take one apart soon to make a video of it. That may shed some light on what is wrong with your switch.

[Richie G]

@SteveJ Thanks for all the help.  I'm going to go back and test again with it completely out to avoid anything weird.  Something must be working for the switch to get them going in low, or I'm incredibly lucky that what's broke broke in a good way 🙂

[Richie G]

@SteveJ OK, embarrassing brain fart alert now that i have it pulled from the car.  Ashamed to say it but i retested and realized as I was doing it that the first time I tested i was actually moving the headlight from off to low/high and not the wiper twist! 😞

With correcting that dumb mistake my results exactly matched your projections (ones in yellow).  I also tested the YG - YB connection when switch engaged which i don't think you mentioned and see how the high is different from the low.  maybe in high YG - YB should also have continuity?  Could that be my issue?

 

[SteveJ]

These results make a lot more sense, and it mirrors my testing. Your switch is functioning properly. The next step is to connect the switch, disconnect the wiper motor and test the grounds out there. I'll write up the procedure soon.

[Richie G]

Thanks. So loss of connectivity between yellow wires in high position not an issue?

[SteveJ]

3 hours ago, Richie G said:

Thanks. So loss of connectivity between yellow wires in high position not an issue?

Nope. It's designed that way. The ground for Low drops out when you go to High.

[Richie G]

Great.  Then at least I can put it all back together unless your next testing steps anticipate needing access to it again?

[SteveJ]

Nope. The next test will require the switch to be installed. We know it tests good, so now we will use it to test the wiring.

[SteveJ]

So for this test, you can disconnect the battery negative. In the engine bay, disconnect the 6 pin connector (with 5 wires) for the wiper motor. It's on the fire wall. For this testing, ignore the LR wire. That is the positive.

Testing:

1. Put your meter on resistance.
2. Have the wiper switch in OFF.
3. Measure L to LW. It should have low resistance.
4. LW should not have continuity with LY or B. LY and B should not have continuity.
5. Put the wiper switch in LOW.
6. You should have continuity between B, L, and LW. LY should not have have continuity with the other wires.
7. Put the wiper switch in HIGH.
8. You should have continuity between B, LW, and LY. L should not have have continuity with the other wires.

Ideally you should see this:

Report your results

[Richie G]

OK not so great results.  About half match as indicated in yellow.  The white cells were the opposite of yours.

After a bit i was going cross eyed trying to see everything and keep the colors straight but double checked the results.  I'm sensing there is a pattern here, maybe one of more of the blue wires are in the wrong spot or crossed?  Thinking back to under the clam shell I'm thinking I saw a repaired connector or two, maybe PO pinned them wrong?

I took this pic of under the clam shell.  Look at B harness.  It looks to me that the L-LW and L-LR might be in the swapped position assuming this is the harness running to the wiper motor.  If those were swapped then the "top row" of the B connector would match the "top row" of the harness in the bay having L, L-Y, L-W in sequence and then on the bottom row L-R would be in the bottom right position.  I guess the Greens are the washer?  Or maybe the pair of greens and the L, L-W need to be swapped?

[SteveJ]

So depending upon the build date, you could see some variations in wiring. Here are the connectors for a late 71. The dash to engine harness has a stacked 3-pin connector for the grounds coming from the stalk. For the wiper motor connector, the one I think you have labelled as B, you look at it facing the side that connects to the wiper motor. The indents are at the top.

Top row:

L LY LW

Bottom row:

empty B LR

From the manual:

And here's from the 70 manual in case you have an early 71: (Note that the wiper grounds from the switch are in a 4 pin connector with only the 3 wires coming from the switch.)

IIRC, the wire layout for the motor itself doesn't change from 70 to 73.