Slartibartfast

It's amazing how much room a parts car takes up once it's taken apart.

If you can work out what kind of plug it is, you may be able to find a pigtail for it, and make up a patch harness to avoid modifying either the truck harness or the compressor. Sometimes the pins in the plug will accept a standard size of spade terminal, but of course you want to make sure it's a tight fit that won't overheat or rattle loose.

No worries! Sounds like a fun build.

Nice two-tone! Check for yourself that the parts are actually bad before taking Les Schwab's word on anything. Check the steering box, too. My dad had every joint in the front end replaced on my '95, and the steering didn't feel any better afterwards, because the slop was in the box. They are technically adjustable, but I killed the box in my '93 by attempting this, so I do not recommend it. I replaced it with a VisionOE/BBB reman off Rockauto, which I also do not recommend, because it's worse than what I started with. I'm planning to replace it with a used one that hasn't been worked over by muppets. A few people have had theirs professionally rebuilt by Redhead--sounds like that's the way to go. The stock centerlink on these is not a great design. If you're keeping the truck at stock height, stock tires, and not wheeling it, then it should be OK. Seemed to hold up OK on the '95. I've got a Grassroots link on the '93, which I don't think I could break if I tried, but it's scared me a couple times from the fasteners working loose (though fine-thread fasteners are supposed to cure this). It's also got a lot more drag than the factory parts. I didn't like that at first, but now that it's worn in to where it self-centers again, I appreciate how the added drag mostly stops the front end from exploring the play in the steering box. Unless they're damaged, the wheel bearings can be repacked and readjusted. There are instructions in the service manual. Cardiagn.com has the '90 manual. Do the seal between the hub and the CV while you're in there. Add the strut rod bushings to your list, even if they look okay. The cups fail, the holes wear oversize, the sleeves wear through, and then the rods wear through. IIRC I tracked down 555 parts through Rockauto when I did mine. Some of the boots haven't held up as well as I would've hoped, but I haven't noticed play in the joints yet. I was told at the time that it was a good brand. Don't know if that's still the case.

From what I've read about what goes wrong on VQs, I'd loctite the power valve screws while it's torn down. IIRC there's a coolant pipe between the heads at the back, with a second thermostat, that's a pain to access normally. Same story with the PCV valve. Valve cover gaskets probably need doing. And you already know the cooler is leaking. The service manual is likely your best bet, but the power valve screws writeup may help for the intake disassembly. Nissan used (and still uses!) the VQ in a few other platforms, so you might find a writeup or even a video for a more popular model using the same(ish) equipment. I wouldn't use this in place of the manual, but it might show some work-arounds for special tools, or other things that you should check while you're in there.

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.

Oil in the coolant is never a good sign. Bizarre that the blue schmoo in the coolant would slow the oil loss, though. I diagnosed a head gasket on a neighbor's Toyota last year. No clouds, plugs looked OK, no obvious misfire, though he said it felt down on power. I got an occasional bubble out of the radiator with the cap off, but wasn't sure I'd bled it right when I'd refilled it, so I wasn't gonna call it just from that. The smoking gun was when I put compressed air to one of the cylinders (like you would with a leakdown tester, except I didn't have one, so I just used the air nozzle) and the air just boiled out of the radiator. The combustion leak test should tell you the same thing. A failed cooler could explain the oil in the coolant, but I don't think it would explain where the coolant is going.

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.

Nicoclub has the '06 manual. Hopefully it's there somewhere. Might find something similar in one of the suspension sections. The GI section has the overall height, if that helps. The bouncing sounds like your struts are shot. Fresh ones should deal with that. Might help with the squatting if the old springs are sagged. I don't know the R51 well enough to know what's out there for stiffer springs or suspension lifts.

I think the four-cylinder trucks got the C200 rear end, which does use a crush sleeve. There's a data plate near the wiper motor that should have the gear ratio (HG43 or HG46) if you'd rather track down a used rear end than rebuild yours. If these were available with the V6 in your market, you may be able to track down the H233B rear end, which does not use a crush sleeve. LSD is marked by an orange sticker that says "use LSD oil only," but you should be able to tell by trying to spin a rear wheel by hand with the rear end jacked up. If it spins the other wheel the other way pretty easily, it's an open diff. I haven't found a full service manual for the diesel trucks, but this manual covers the engine. The '90 US-market service manual from cardiagn.com or the '94/'95 from Nicoclub should get you close enough on the rest of the truck. The PD section covers the rear end. Fog lights are a pretty common option, at least over here. Different bumper inserts, relay near the wiper motor, rocker switch on the console, little added wiring. That harness was bundled with the alarm system on mine, suggesting it was installed at the same time, probably by the dealer. Neither system is in the service manual. The only black and red switch I remember seeing on one of these was a Russian (?) market hazard light switch. If your mystery switch isn't the same style as the rest of the dash switches, I would assume the PO added something. Follow the wires. And yeah, gotta host pictures elsewhere and link them in, unfortunately.

I haven't tried swapping calipers, but I do have some WD21 front brake parts laying around. Let me know if you need measurements.

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. 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.

Haven't seen Pete around in a while. This should have what you're after.

Heat and torque. Aluminum and steel can get pretty stuck on each other. If it won't break free, try turning the other way, then back again. I got lucky on a brake line the other day by getting it hot and melting candle wax into it. Took a while, but came out without breaking anything.

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.

Should be good enough.

Wow. Yeah, that's not right. I'd be interested to see pictures of the insides to see what let go. Make sure your diff donor has a V6 (four-pots got a smaller front diff) and the same number on the data plate by the wiper motor. HG46 is 4.6 gears, HG43 is 4.3 gears. I've worked on a couple of GM 4.3s. Shakes like hell because it's a 90* V6, weird fuel injection. That said, they do have some decent torque. Someone on here had a 4.3-swapped WD21 around when I joined up, though naturally I don't remember their username. I think there was a solid axle swap involved.

NPD lists 92600-57G00. Still available, possibly because they want so much for it. Weird that the thermal protection switch is missing on the aftermarket ones. I wonder if they built it into the coil, or if they just didn't bother with it at all.

Yeah, that could explain a few things. The wire is a good get-you-home fix, but I recommend picking up a replacement ground cable, or at least a new terminal end.

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.

Lots of good info around here for R50s. Download the service manual from Nicoclub if you haven't yet, may come in handy with the engine swap. I don't think I've heard of a power valve screw locking one up before, that's gnarly. Your pictures aren't showing up for me.

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. 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.

Keeping older rigs alive can be a bit like playing whack-a-mole. Hopefully the MAF mole stays down for a while! When my stock 70A alt started making threatening noises, I swapped it for a 90A Maxima alt. Plugged right in. IIRC it was actually cheaper that the 70A. I don't know that the truck needed another twenty amps of headroom, but it's got it now. I don't remember if there's a similar parts-bin upgrade for the R50, but it might be worth looking into if you've gotta get in there anyway.

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.

Mine's needed this done for longer than I've had the truck. I bought gaskets, studs, and a 90 degree drill adapter shortly after we got the truck, and then I never got around to it. My engine is also a little tired, and the rear main is leaking, and I've got a VG33 in the corner waiting for me to get around to it, so chances are I'll keep ignoring the exhaust leak until I'm ready to swap the engine. The VG33 has a little more displacement, larger exhaust manifold studs, a larger crank snout, a better oil filter location, and a couple of other minor improvements. It's mostly bolt-in, and will run off the stock harness/computer/fuel system if you swap a few things over from the old engine. It's also got flat belts, and a different balancer, so there's a little screwing around required there. David Carroll/Mr. 510 makes (made? Don't know that he's still selling them) adapters that replace the balancer so you can run the old V belts and accessories. You will need to modify a VG30 water pump if you do it this way. (Details in Mr. 510's VG34 build thread.) I have read that the Xterra/Frontier accessories and brackets will fit in the WD21 engine bay, but the R50 Pathfinder ones won't, though I think someone managed to make them work with a little modification. I have heard of people swapping the VG30 crank into the VG33, to keep the old balancer, but it sounds like a lot of work to use an inferior part (the smaller snout of the VG30 crank does sometimes have issues). The VG30 cams are supposed to be a drop-in upgrade over the VG33 cams, so hold on to those. The oil pan and pickup may need some screwing around depending on your donor. I've read that VG30/33 heads can be swapped, but the cooling passages are a little different due to the larger bore, so it's not exactly ideal. If I was going to pull a head, I'd just fix the old head on the bench (without a truck in the way!) and then put it back on.