Jump to content

Figbuck's 620 AlternateReality Tour


Recommended Posts

1973 620, L16, was stock for 40 years but slowly one thing after another is either failing, failed or else driving a daily driver with broken shit just gets old. I would love to have windshield wipers that work, headlights that aren't dim when I tow a trailer at night, etc.


A long time ago for some reason, my headlight circuit overheated the wiring/plugs to the lamps and melted the upper corner of the fuse block where the 20 amp fuse is. I replaced the fuse block but the wiring insulation and plugs to the lamps are old and brittle. Maybe ten years back I was a long ways from home and my headlights quit. Some guy stopped to see if I needed help and took me back to his garage... took the headlamp relays apart. They were pretty decent inside but the press joint where the wiring tangs on the outside mate with the coil and switch on the inside. Those joints finally made the continuity so sketchy it wouldn't trip the relay. He shot a dab of something to clean the copper, neutralized it and then soldered the joints through the back of the relay.


I would like to clean up the whole headlight circuit with new relays, wiring and plugs. It ain't broke, but shit looks like a short in progress. 


I'm running a stock 35amp Hitachi that was rebuilt at a shop less that 30K, so it's not something that I need to do immediately, because I'm not towing a trailer in freezing driving rain at night every day.  But, I have wanted to upgrade the alternator for years and just keep procrastinating... so maybe if I get all the right stuff collected, I will get it done.


I went to P'nPull yesterday to survey what was actually in the yard and started my AlternatoReality Tour...




So this is not on deadmonkey's list right? Why not? it looks like it will work...






Right down the row was another one...














This second truck looks like a better alternator. Am I on the right track or not?

Link to comment
  • Replies 12
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

That is an LR150 new style. It will work

* fit longer belt

* adapt oval plug to harness

* unplug regulator amd jump two wires at the regulator connector


I would get a 1979-1980 LR135. It is a direct bolt on and only needs the last step (regulator unplug and two jumper wires).


Or use a 1978-1985 LR150 with the stock t-connector.

Link to comment

Couple of things.


The 38 amp alt. you have is a smaller diameter and fits the small space on the front of the 620 truck. All other Nissan alts are physically larger and tend to rub the idler arm grease fitting and/or the bottom rad hose inlet just above it.


All Nissan alternators after '77 had an internal solid state regulator so your electrical system will need to be modified as it had an external mechanical voltage regulator on the fender behind the battery.





Cleary this one is an '85 720 alternator that was also used on the Z24i powered D-21 Hardbody and the WD-21 Pathfinder. It's 50 amp output, a modest increase. The KA alternator for the later Hardbody is much the same, has a Vee pulley still and is 90 amp output.



You will have to join your two wires to the ones on this plug. I did this with my 710. 

Link to comment

Never fails, I get to the last photo and a half hours work crashes. There were 3  720,s  3 '9o's  Hardbodys, 3 early '90s Sentras and 2  '87 Pathfinders in the yard. I'm curious why there are all these different alternators in just a few years fro '85 thru '88. Why are the '87s different than the '88s?






Looks like a reman huh?




The next one was a '93 Sentra. Is this a KA? I don't know this stuff... I'm an L guy. How about this alternator, it's a compact little unit. The 'legs' look kind of long where they bolt to the bracket/pivot, but the width looks right. How many amps? Internally regulated?






Hey how about this coolant neck? I didn't have any tools with me. Looks like it would bolt to the L16 block! Do you think it would work? I swear I have not seen a 280Z or L28 Maxima or any of those swept back coolant necks for like ten years. 






So the last one is maybe the hot set up? The '87 is on the list at 105 amps.










Bueno, no?

Link to comment

I'm curious why there are all these different alternators in just a few years fro '85 thru '88.

Because Nissan was run by the engineers to bankruptcy until they were bailed out by Renault. For example they had four different 2-liter engines that year.


KA is a big four cylinder and was only fitted to larger Nissans. Sentras came with 1.5 to 2.0 liter engines

Link to comment

Yeah I kinda do tow a trailer a lot. And I have a fog lamp that is mounted on a bracket next to the license plate, connected to my back-up lights. The light shines bright so I can look in my left mirror and back in long driveways ways easily, and back a trailer at night. But mostly running at night in the rain, with heater and stereo on is not good. Hit the brakes and the trailer lights dim the headlamps... which are dim enough to begin with.


So is the nomenclature stamped on the alternators?  How do I tell if its and LR135 or LR150?


Is this a 1600cc or 2 litre engine in the Sentra I pictured?






I was interested in this one because it seemed compact and a later model year so it is internally regulated...


I looked it up and its 70 or 80 amp but it has a 4 groove pulley. I don't really want to mess with changing a pulley unless it fits right in there. 

Link to comment

Thatsa GA16DE. It will say on the underhood aluminum plate.



So is the nomenclature stamped on the alternators? How do I tell if its and LR135 or LR150?

Some have it on the metal tag, like on your first pic.


Every Datsun from 1978 up has either the small LR135 or large LR150/LR160.


The last external regulators were used in the 1970s.

Link to comment

EFI engines need constant power and can't work properly if the voltage drops from headlights, heater and wipers being on. Engine size doesn't necessarily mean it has a lower output alternator. Most if not all alternators today are around 100 amp. Today's cars are loaded down with heated seats, mirrors, rear defrost windows, courtesy lights you name it.


If it has the factory alternetor it will have a small metal foil sticker saying what part number and usually the output. I got a 2002 Altima 100 amp for my 710 but cars have more room for these larger ones. Cleary, the Hardbody alternators after '90 are 90 amp and Vee pulley, all others are serpentine type. Use the search and look up alternator swaps into 620 for some alternative ideas... maybe the GM Saturn alt? Has to be small enough to fit the trucks small space.


The last external regulated alternators were used in '77. All were internal regulated in '78.

Link to comment

Thanks for taking the time to talk to me guys. I have read everything that a search will find on 620 alternator swap. Some of this stuff I have read over 'n over, and book marked pages, so I can refer back to it. Most of the info I probably read when it was first posted years ago. But until I actually do something, I don't retain some kinds of information well. Once I experience the process and actually do it, I own the knowledge, it's not abstract or just theoretical information.


So, I grabbed the alternator out of that last truck I pictured. It's remanufactured but it looked cleaner and newer than any of the other ones.  For $24, if it dies... I can slap another one in there.




This 35amp Hitachi was the fifth one in the life of my truck... and it's still cranking out 35 whole amps too! I guess that is my issue. I usually got 60 or 70 thousand miles on one before the diode would go out. You-used-ta could go to the dealer and get a new diode for like six bucks and fix it. Except by then the bearing would be next to fail, so for all the hassle of crawling under there to fool with it, you could bolt in a new OEM alternator for $73 from the dealer. Then the dealer price went way up in the '80s, but you could get new Bosch units for like $90 that were way better I think. That one seemed to last the longest anyway. Note how much room there is between the coolant neck/hose and the alternator.




If you look really closely, the belt looks a little crooked. Both the bolts holding the lower bracket to the block were backed out a 1/4"... it was pretty crooked! How does that happen? According to my maintenance log it's been in there for 30K  mi. 




For me the hardest part of removing and replacing the alternator, was needing two different size wrenches to loosen the bolts/ nut that the alt. pivots on. I decided to cut the welded nut off, so now all I need...




is a 13mm socket & combination wrench to turn them. I put the alt. on the bracket first, then wiggled it up from underneath with out having to deal with the radiator hose. Tight fit with the same belt I was using! There is about an inch of room between the steering idler, and the fan/pulley misses the radiator hose about the same.  




Tight fit.




I snipped a couple short pieces of #14 romex, trimmed some insulation and pounded the exposed wire flat with a hammer to fashion ratsun hotwire pigtails, and bypass the voltage regulator. I took it for a test drive to the auto parts store for a longer belt, some dialectric grease, contact cleaner and stuff to clean this rats nest up.




One of the reasons I put off doing this, is that I knew once I got started, I would see all kinds of other sketchy stuff that needed to be redone. Sure enough there were corroded grounds and frayed wires... as long as it was covered with grease and dirt... it looked fine.  Nothing ever takes an hour or an afternoon. It me takes that long to get thing clean enough to work on it. Plus I'm working out of carport with no power, and a landlord who just jacked the rent, and hates tenants working of cars.


I have a bunch of different wiring schematics for 510/ 620 in general and specific to '73 also. The color codes on my truck don't always agree with the manuals. Also as I started to trace out individual circuits and systems, I find that my wires are not really routed the way it seems on the drawing. I needed to strip the wrapping off the looms so I could trace circuits out, regardless of the wire colors.


At this point, I was burnt to a crispy critter and needed beer... so the truck fired right off. 14.6 V @ 800RPM at the fuse block. The engine sound a little different. The whine of the old alternator trying to keep up is gone. For the first time I can actually hear my turn signals click fast. Before they were so slow and weak. The heat/defroster fan cranks, I even forgot that there were dash lights!  Now I has'em. 


As I was driving I had the thought that my electrical issues recently, have been not so much not enough current, but bad grounds. I'll give you a carpenter analogy; you use a carbide blade on a chop saw and only make a few cuts a week. It takes the blade a year or more to get dull... but it happens so slowly, you forget what a sharp blade is like. Like every time I put a new set of strings on my my old couch guitar, that i play while I watch the TeeVee... damn, those old strings were torched! 


When I rebuilt my engine in the early '90s, I got a pretty nice AutoMeter oil pressure gauge. When I first put it in, I thought it was not calibrated very well because it read 20 or 25 lbs. at idle and maybe 40 lbs. at 4Krpm. At first I freaked out... 20 lbs. this thing is going to grenade... but the engine ran great. I figured it was a glorified idiot light. As long as it registered a pressure... and I don't hear valve noise! I looked down at the oil gauge and it was over 40lbs at idle, and 60 lbs. at 3Krpm!  Hahaha, it never had enough current to read right! Fuck man I laughed so hard. Well you had to be there maybe. 


So far, so good. My alternate reality tour continues. I hope I can get this wrapped up today.

Link to comment

Looks like I saw this a little too late.  I run the free replacement for life, yes the autozone alternator.  I have it in my 620, external regulated, no wire cutting, and is a 60amp.  Have had it for a few months with no issues and if it goes, I get another for free.


Just go in and ask for a 510 with AC alternator, bolts right up and cost $25, can't beat that.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.