'87 Pathfinder-Rear wiper won't turn off

[Fbanks]

I finished the tailgate switch- it was not effectively shorting when the door was open due to corrosion and bad contact. I cleaned it up real good, and bent the contact down a little until I got a good, consistent short, but still got an open when depressed. The mechanism itself seemed to be fine, and I could see it open the contact gap when pushed in, giving an open. It just wasn't getting a good short when in the released position. While I had it unplugged, I went ahead and tested the cargo lamp by jumpering the connector. Even with that, the only way I could get the cargo light to come on was by turning it to the "ON" position. I thought maybe it was the cargo lamp switch itself, but when i checked at the connector, I had 12v across Red/Grn and black, but 0v across red/grn and red/wht. So something else is off there. 

[Slartibartfast]

The Terrano is just what they called the Pathfinder in some other markets.

 

I may have one off my parts car. I'll dig around later and see if it's got a part number on it.

[Fbanks]

Many thanks, I appreciate it, and all the help you've provided! 

[Slartibartfast]

I found it, but I can't guarantee it'll work in yours. The sticker says 28510 83P00 ('89-'95 according to NPD). Replaces 28510-83G00 (also '89-'95). Not listed with yours. The one that replaced yours (B8510-42G85) is listed for '87-'94, suggesting that there wasn't a design change in '89. 43G85 also replaced 28510-30R00, '89-'95 Nissan Axxess (a model that I didn't know existed until just now), which is not listed as fitting an '87 Pathfinder, which makes me think their compatibility check is whether it's original equipment, not whether it'll work. I would be kind of surprised if the 83P00 didn't work in yours--but at the same time, not that surprised that Nissan found another dumb thing to change for no obvious reason. I'll dig out the '87 manual later and see if the wiring diagram looks the same.

 

It might be worth seeing if you can get yours open. If it's like the door lock timer, the plate where the plug is should sorta pry out where it's snapped into the box around it, and then the whole circuit board and plug should just slide out. Might be something obvious and repairable. Relay welded shut, cracked solder joint, capacitor dumped its guts, something like that.

[Fbanks]

Thanks for checking! I'm pretty sure I tried to pop mine open, as I did see a tab there. When I pushed on the tab though, it broke off and fell inside, so I quit there rather than force the issue. I'll pull it out again and give it another try. I left the panels off for now so should be quick. 

[Fbanks]

I did manage to get it apart. There are small retaining tabs top and bottom, and if you get a small screwdriver between the plug and the casing, it pops out. The "tab" I thought Iwas pushing on was a retaining bracket for the plug pins. I don't think it's all that necessary, but I glued that back into place, and it should hold fine until I can get a replacement. Upon inspection, I did not see anything obvious on the board. All the solder points still looked nice and shiny with no obvious breaks, and no obvious burns anywhere on the board.

 

I began to doubt my earlier test results, so I connected it back up again per the diagram in the service manual. When I connected the voltmeter across pins 2 & 7, I forgot that I still had the meter set to ohms. When I applied the power, a couple of the leads I was using for power/ground were quickly smoked, and the insulation burned back (kinda like my fusible link, though these were very thin alligator clip jumpers I had laying around). I quickly removed power, and set the meter to the DCV setting, and tested again. As before, I was still reading a negative ~3V. I plugged the amp back into the truck to test the function, and it still functioned just as it had before, so I guess no harm done with my mishap. 

Edited May 31 by Fbanks

[Slartibartfast]

I dug out the '87 paper manual. The diagram looks the same, but the test is not. EL-89 in the '87 manual wants the test light across 2 and 4, not 2 and 7 like the later manuals. Give that a shot and see how it goes. Unfortunately it's got the same head-scratching description. (And it calls the box a relay rather than an amp, despite using the same drawing.)

 

 

I don't know why the test procedure is different. The wiring for pins 2, 4, and 7 goes to the same places in either diagram. In fact I can't find any difference between the '87 and '89 rear wiper wiring diagrams. The '90 diagram has some routing/plug differences but looks like a different organization of the same bits. '95 complicates things by moving from a nine-pin switch to a four-pin switch with a diode and another relay making up the difference, but the wires from the amp all appear to go to more or less the same places. So, again, I can't say with any certainty whether the '95 amp on my bench would work in your '87.

 

Speaking of head-scratching, the test does not specify whether it's for the front or the rear wiper amp. Both amps use an eight-pin plug with one pin missing, but the front amp is missing #4, and the rear amp is missing #8, and the test diagram clearly shows a plug missing #8, suggesting it's gotta be the rear amp. There does not appear to be a test diagram for the front amp.

 

On 5/31/2024 at 9:08 AM, Fbanks said:

these were very thin alligator clip jumpers I had laying around

 

I bought a set of cheap jumper leads a while back, and was surprised to find that they were made with iron-core wire. I've taken apart some cheaply-made junk, but that was a new one. I could pick up the wire with a magnet, and they melted really easily. But, yeah, better to smoke a cheap jumper than blow up the meter, or an unobtanium wiper amp from the '80s. My usual trick is forgetting I had the meter on amps and blowing the fuse trying to test voltage.

 

What's on the board? Any obvious relays in there? If you can work out which pins should be open/closed when the relay isn't energized, and test across those, you should be able to work out if one of them is stuck on.

[Fbanks]

Hey, thanks for digging that out. I retested the amplifier module again, this time with the voltmeter across terminals 2 and 4. Before connecting the power, the voltage was floating around 0.2v. When I connected the power, I could hear at least one relay clicking, and the voltmeter went to a solid 0v. 

 

11 hours ago, Slartibartfast said:

I

What's on the board? Any obvious relays in there? If you can work out which pins should be open/closed when the relay isn't energized, and test across those, you should be able to work out if one of them is stuck on.

 

Mostly there's capacitors and resistors on the board, along with a diode or 2. There are 2 larger boxes on the board with the following markings- Omron G8S-1117P-CUK. They look very similar to these relays on Ebay, that have the same part number, but without the "K" on the end (mine also have the number 24Z6DK underneath this part #, instead of 1180D6)

 

https://www.ebay.com/itm/142203152250

 

Whereas these appear to have only 4 legs, mine have 5 solder points, so I'm assuming they would have 5 legs as well, though I have no idea why? I thought maybe they were just socketed in, and that I could just pull the body of the relay out, but that doesn't appear to be case, and it looks like the legs are soldered directly to the board. 

 

 

[Fbanks]

Looking at the back of the board where the solder points are, and with the 3 terminals on the top, and assuming the layout is the same as that 3rd picture in the ebay posting above, I made an attempt to energize the relays. I assumed the coil would be across terminals 1 and 2, with terminal 1 being the top middle, slightly offset pin. Terminal 2 should be the pin to the right of it (looking at the underside of the board. When I put power across these terminals, I hear a buzzing (but no clicking, like I did from the test above) from one of the relays, but not the other. If I reverse the power/ground leads, and do the same, then I get a buzzing from the other relay, but not the first. I don't know why this would be, as the relays appear to be identical, and appear to be put in the exact same way. 

 

Anyhow, I have no idea what that means, as I made a couple assumptions- 1) I assumed the pinout matched that in the ebay posting, and 2) I assumed that the coil was across 1 and 2. Either of these could be bad assumptions.

[Slartibartfast]

I think you've got the pinout wrong. This datasheet for a similar-ish PN shows the same pin arrangement as the eBay listing (except that the #4 pin that's stumpy on the eBay ones is full-length). Looks like 2 and 5 are coil, 1 (at the end, between 2 and 5) is common, 4 is normally closed, 3 is is normally open. 2 and 5 should make it click, 1 and 4 should have continuity when the coil is not powered, 1 and 3 should have continuity when the coil is powered. Worth noting that testing components in the circuit can be confusing as hell, as other components and connections do things you don't expect. It may be necessary to desolder the relays and test them off the board. Probably safer for the other components on the board as well.

 

The buzzing sounds like you're energizing the coil through the normally closed contact. Coil gets power, contacts open, coil loses power, contacts close, repeat however many times a second. Same as how a horn works.

 

Clicking suggests at least one of them works. Hopefully the other one is the problem. The amp failing both versions of the test suggests that you're looking in the right place.

 

 

Edited June 3 by Slartibartfast

[Fbanks]

Thx for that diagram- I tested the relays according to the diagram, and both relays acted just as expected. I had continuity from 1 to 4 when not energized, and when I applied 12V across terminals 2 and 5, I could hear the relays click, and I had continuity from 1 to 3. I also checked the other contact in both energized and non-energized states, and while not a complete open, I had something in the megaohms range on the open contact.

 

I did not bother to desolder them from the board since I got the expected response. Just to be sure, I retested the amp again according to the service manual, and once again obtained the 0V across terminals 2 and 4. 

[Slartibartfast]

Sounds like the relays are ruled out then. How are you with troubleshooting circuit boards? My next step would be trying to draw out as much of the circuit as possible, to see how power should be moving through it when it's wired up for the test, then go through that path with a meter to see if you can find where power (or ground) is getting hung up.

[Fbanks]

I wouldn't say I'm a great free-form troubleshooter. Give me a schematic and I can maybe figure a few things out, but I'm not sure if the traces on the board are even visible for me to follow. I'll take a closer look when I get a chance. I could try ohming it out, but that might not be that easy since I can't isolate the components easily, not to mention very tedious. I feel like I'm just close enough now to solving the problem that I hate to quit, but far enough away still to question if it's worth the effort. I might also try investigating some more junkyards, to see if I get lucky. I am concerned that if there are a bunch of different (and relevant) variations of this amp according to model year, it could prove to be a very difficult search, as I'd basically be restricted to '87-'88 pathfinders vs. '87-'94

 

On 6/2/2024 at 2:24 AM, Slartibartfast said:

The '90 diagram has some routing/plug differences but looks like a different organization of the same bits. '95 complicates things by moving from a nine-pin switch to a four-pin switch with a diode and another relay making up the difference, but the wires from the amp all appear to go to more or less the same places. So, again, I can't say with any certainty whether the '95 amp on my bench would work in your '87.

 

I was initially a little confused by this, but when you're talking about going from a nine-pin to a four-pin switch, I think you mean the switch on the dash, right? And the pins on the amp connector (and the wires  are the same? If so, do you think performing the fucntionality check in the service manual on your module using pins 2 and 4 would suffice as a compatability check? 

[Slartibartfast]

The switch, yeah. Square-dash has a rocker switch on the dash, round-dash moved it to the end of the wiper stalk. The wiring to the amp looks mostly the same, but it's hard to say for certain given the different switch and the stuff they added to make that work.

 

12 hours ago, Fbanks said:

If so, do you think performing the fucntionality check in the service manual on your module using pins 2 and 4 would suffice as a compatability check? 

 

That's a good idea. I'll have a poke at mine later and see if passes one or both tests. Might also be a good sanity test for if we've got the test procedure right.

[Slartibartfast]

So I had a poke at mine, and didn't have any luck with the test either. Then I looked at the diagram again, and the wording that made no sense, and I think I may have worked out what it's actually supposed to mean. I think the lead from battery ground to #6 is another test light, probably the screwdriver-with-a-bulb-in-it type, judging by the picture. You're still grounding #6, but through resistance, I guess? When I tried it this way, I started getting results.

 

So that's 1 and 3 to ground, 5 to +, 2 and 7 or 2 and 4 to the test light they bothered to label (which I assume is a dummy load for the wiper motor), then clip the screwdriver test light's lead to ground and touch the tip to #6 to trigger the amp.

 

The amp clicked when I set it up. If the dummy load light was hooked between 2 and 4, like the '87 manual says, when I triggered the amp #6, the amp clicked and the dummy load light lit up and stayed on until I disconnected power. If I wired the dummy from 2 to 7, the relay clicked when I triggered #6, but the light did not come on, and the amp clicked again a moment later, like it could tell that there was no load hooked up and it was going back to sleep.

 

I never saw the bulb in the screwdriver light up.

 

If my current understanding of this really poorly documented test is correct for a change, then this amp tests good by the '87 manual, and bad by the '95 manual--which is bizarre, because it came out of a '95 with a working rear wiper.

 

Try the test with two test lights, see if that makes yours do something. I won't get to it for a few days, but I'm thinking I'll try plugging the '95 amp into my (square-dash)

'93 to make sure the amp is compatible with the earlier controls.

[Fbanks]

On 6/7/2024 at 4:39 AM, Slartibartfast said:

You're still grounding #6, but through resistance, I guess?

When I tested before, I had pin 6 going directly to ground. I totally missed the screwdriver looking thing in the diagram, or took it for a banana plug jack or something. That's a good catch!

 

I was also just using my voltmeter in place of the test light, across 2 and 4, or 2 and 7. I think I have a couple of inline spark testers around somewhere that I guess should work. I'll see if I can dig them out and give the test another try. 

[Fbanks]

I went to test the amp module again according to your post above, but I immediately noticed something was off. I had left all the wires connected to the amp module, with the clips to the marine battery I was using for test purposes just clipped to the battery case, next to the terminals. But, I noticed the positive and negative terminals on the battery were in reverse order of where I thought they were. This means the previous testing I did when I went to replicate my first test, except now to measure across terminals 2 & 4, were invalid. I must have used the marine battery and put it back differently in between my original test, and the retest. 

 

I corrected my error, and tested again as I had previously. When I connected power to pin 5, I could hear the relay click, and I never heard it disengate. When reading across terminals 2 and 7, I got -2.3V, which is close to what I had gotten in my original tests (I did have different leads, so this seemed reasonable). But now, when I read across terminals 2 and 4, I got a -12.5V. It did not seem to matter whether I had pin 6 going to ground directly, or going to ground through one of my inline spark testers, or completely disconnected. The -12.5V was with the positive lead from the voltmeter going to pin 2, and the negative lead going to pin 4. 

 

Maybe the behavoir above with the disregard for pin 6 connection is consistent with what my rear wiper is doing (never cutting off)?

 

Side note-I don't think those inline spark testers work as DC test lights, as I could not get mine to light up even going directly across the battery terminals.

[Slartibartfast]

Spark testers use neon bulbs designed to work at high voltage, so, yeah, no good for 12v. You can make up a test light pretty easily with a 12v light bulb (194, 1156, whatever's handy), a test lead you don't mind cutting in half, and a soldering iron.

 

And yeah, I had assumed that was a banana jack or something too. Nice that they couldn't be bothered to label it.

 

Mine clicked once when I hooked up power, then clicked again when I triggered pin 6, and did not click off until I disconnected power. If yours has power across 2 and 4, when you haven't triggered pin 6, I'd call that a smoking gun for the amp.

[Fbanks]

I agree. I'm going to take a closer look at the board when I have some time to see if I can find anything defective that I can fix myself. I'm not real hopeful on that, but I figure it's worth a shot. 

[Fbanks]

I did some more inspection and poking around on my board tonight, but failed to uncover anything. I think I'll have better success putting my effort into finding another amp unit, unless you want to part with yours? From your post above, I do believe that I should be ok with Pathfinder models from '87-'95. 

[Slartibartfast]

I want to test the spare amp vs the one that's in mine to make sure it's good before I box it up. But, yeah, it's not doing me any good gathering dust on the bench. PM me and we'll sort it out.

 

Might be worth checking the diodes on yours, if your meter has a test mode for that. They can fail open or closed (or fail closed and then burn open), and I imagine either condition would play hell on whatever logic circuit they were part of.

[Fbanks]

I do have a diode mode on my VM, so I took a look. If I'm right, there are 4 diodes on the board, 2 oriented at right angles to each other toward the front of the board, and 2 oriented at right angles to each other toward the connector side of the board. I'm not sure that the diode test is valid with them still being soldered on the board- only on one of these diodes (the one just in front of the connector) did I get the expected 0.7V in what I think was forward-biased condition. When I reverse-biased, I got 0.5V. For the diode beside the connector, I also got 0.5V when reverse-biased, but 2.0V when forward-biased. 

 

For the front-most diode toward the front of the board (the only one laying horizontal), I got 0.2V in both forward- and reverse-biased states, while I got 0.1V in both states for the other.

 

I note that when in diode mode on my VM (Fluke 79), and the leads are totally open, the VM reads 2.4V. That doesn't seem normal

Edited June 17 by Fbanks

[Fbanks]

I decided to check the diodes with another meter, since my diode test on my meter seemed questionable. First, I should note that for all the readings I reported above, the forward- and reverse-bias notations should be reversed.  The voltages listed were correct, at least according to that meter. 

 

With the 2nd meter, I got the following readings:

 

Diode 1 (just in front of connector)- Forward-bias 0.575v    Reverse bias 2.98v

Diode 2 (beside connector)- Forward-bias 0.575v    Reverse bias 1.4v

Diode 3 (farthest from the connector)- Forward-bias 0.5v    Reverse bias 0.58v

Diode 4 (just behind diode #3, next to chip-looking thing)- Forward-bias 0.28v    Reverse bias 0.28v

 

I'm thinking to test these properly, I probably need to desolder/disconnect the cathode end of the diode? Diodes 1,2, and 3 appear to be the same, and have a 6.L marked on them, while diode #4 has a 6.8 marked on it

Edited June 17 by Fbanks

[Fbanks]

Final resolution- it was the rear wiper amp module that failed. I got a replacement unit and tested it, and all switch positions worked perfectly (interval, on, off, and wiper). The replacement came from a '95, so that confirms compatibility of unit from  '95 model with that of '87 model  Whether it was the fusible link failure that initially caused the rear wiper amp failure, or vice versa, we'll never know.

 

Many thanks to Slartibartfast for the diagrams and all the guidance provided, as well as the replacement unit, which got me back fully functional again.

[Fbanks]

I'm adding on to this topic, since it might be related, and could be the reason for the original failure. The original failure started with a fusible link burning up, and the rear wiper started to run continuously after that. Rear wiper issue was resolved with replacement of the rear wiper amplifier unit. Flash forward to yesterday, and the truck was running fine, when a light mist started. I turned on the front windshield wiper, and noticed that the wiper seemed to run the same speed regardless of switch position, and the wiper also would not stop, even with the wiper switch in the off position. I don't drive the old truck that much anymore, but I do recall having this issue with the front wiper not stopping periodically in the past. Also, I recall the intermittent function rarely, if ever, worked anymore. I didn't worry too much about this, since I when I stopped the truck, the wiper would also stop, and would not resume when I started the truck again so long as the switch was in the off position. 

 

So back to yesterday- I shut the truck down when I could to kill the wiper, but when I went to restart, the truck would not turn over. I was luckily on a hill, so attempted to jump start her with the clutch. She did attempt to fire a couple times, but would not stay running. Took a look under the hood and failed to see anything obvious, but when I tried to start again, it turned over just enough to crank, and seemed to be running fine. Continued on my way until maybe 10 miles later going down the highway the truck just died, along with the instrument cluster and all power. You could hear the hazards clicking when I turned them on, but they were too weak to flash. Luckily, my brother was close by and was able to give me a jump, and the truck started fine. Checked some voltages and it appears the alternator has gone bad, and was unable to charge the battery. This behavoir continued as I made my way back home with the truck, having to get a couple of jumps along the way. I paid attention to the voltmeter on the truck on the way home, and noted that just after jumping, it would be at 12 volts and never got above that. At times, but not always, it would begin to drop and when it got down significantly below 12v, the truck would just die. 

 

Long story short-I believe the alternator is intermittently failing, but it made me wonder if this might not have been the cause of my fusible link and rear wiper amp failures earlier? I can't recall if the voltage regulator is built into the alternator or not, but perhaps it was putting out too much at some point and burnt the fusible link and the rear wiper amp? I'm planning to replace the alternator, which hopefully solves my problem, and also the issue of the front wiper speed not changing (i'm guessing it just didn't have enough juice to go faster). I don't expect it will solve my old problem with the front wiper, and I'll probably have to decide if that's worth fixing or not. I'm wondering if there's a front wiper amp, like the rear wiper amp? I'm thinking I recall briefly looking into this before, and hearing that the front wiper intermittent function was built into the wiper motor itself? 

 

I did inspect the fusible link after this episode, and it seems to be perfectly fine. So far as I can tell, there doesn't appear to be any electrical issues outside of the failing alternator. Any thoughts/advice on 1) the alternator being the cause of the earlier failures? And 2) potential causes of the front wiper failure to stop/intermittent wiper not working?