75 280z Washer pump blowing fuses

[Dave WM]

Been down this road before, cropped up again. Intermittent blowing of fuse to wiper only when using the washer pump push switch on the combo switch.

1st I disconnected both the pump AND the wiper motor, it will still sometimes want to blow the fuse (I can see it on the amp meter, so I release quickly to save the fuse). It will sometime work fine, other times there will be a 30amp looking surge per the amp meter (and blow the fuse if I don't get of it instantly). Since it does it regardless of the wiper motor or washer motor I am going to hope its not the wire harness (its all in real good shape from what I can see) and assume its either the combo switch or the intermittent wiper relay. On the switch I can see a battery lead think it was B and I that connect with the switch is activated (for the wiper action anyway) I think the pump was just a ground so I don't think a problem there could blow a fuse.

As for the relay, I can see a capacitor from the lead that connects batter voltage thru the switch to the ground. Maybe the cap is starting to short? its a major pita to get at the relay and I would think its a less likely candidate for the problem (shorting cap) so will start with the combo switch. Being intermittent will make it a challenge to find the issue, will start by unplugging it and seeing if I can get a tone by connecting one hot lead at a time to the ground and pushing the button. Or I could try testing my spare 1st and see if it passes the various continuity and ground fault test, if it does just install it.

wondering if anyone else has experienced this failure mode (fuse blows ONLY when using washer and ONLY intermittently).

[JSM]

Hey Dave, might want to unplug the washer motor itself first and try the wipers and push the button without it connected.   Maybe the motor is going bad for the washer pump. 

[Dave WM]

did that, in fact had both washer AND wipers unplugged, still draws massive amps just pushing the washer button, sometimes...

 

[SteveJ]

Do a visual inspection, looking for damaged insulation or signs of melted tape on the harness. If the problem is with the switch, you should be able to see it grounding out either against the switch body or the ground wire (orange arrow in the attached image). The pins that have color are the only ones that should not be grounded during normal operation.  If I understand you correctly, you should check the pins at the green and blue squares for continuity with the ground wire and switch body when you press the washer button. You can disconnect the 9 wire connector and ground wire to test.

[Dave WM]

Yes Steve that is the exact plan I have. I check the B&1 (green and blue) on my spare combo switch just to make sure neither should ground during operation. I did look closely at the donor to try and see exactly how that could happen, too look for a weak spot, trying to better under stand the possibility. I plan to give it a go later today, will report back on the test. IF it test out the next test will be to unplug the intermittent amp from the body harness and see if it still causes the momentary short. If it does (and if the combo switch test ok) then I can assume I have a harness issue between the combo switch and the intermittent amp.

[Dave WM]

dumb dumb dumb.

Ok when I 1st got the car, the combo switch headlights were jammed so that the wiper would not go to the off position.

I must have taken it apart and got that fixed (the rotation part) and apparently when I reassembled I goofed a insulator that ls used to mount the wiper switch (BLUE on Steves diagram) by mounting it in such a way that theinsulator did NOTHING to insulate the blue wire from ground. Got it all back together and looking good. Thanks Steve!

video to follow..

 

 

Edited August 14, 2017 by Dave WM

[SteveJ]

Nice breakdown in the video. Good diagnostics starts with a good problem description. When you had it isolated to the switch, you and I could both see how it needed to be tested. Once you isolated the component, you could find the root cause. That's exactly how it's done. Not once did I notice you wanting to "throw a part at it" to fix a problem. Hell, even I have been guilty of that many times.

[Dave WM]

What really gets me is self inflicted wounds. I should have premised my problem with "I worked on it once to fix the wiper motor switch". Its those kinds of clues that rarely (like my case) get stated. That is just the kind of thing that would then follow up with "are you positive you put it back together right" anyway I am thrilled it finally nailed down. It's odd that it would not blow the fuse EVERY time I used it, perhaps there was enough resistance in the points of the switch to

• not blow the fuse
• not drop the voltage below the threshold of being able to activate the wiper motor.

I prob did some damage to the points, but I did not use the switch much so hopefully not a big deal.

[jkeese01]

I did the same exact thing on my 1977 280z. 

Thanks for the video.