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My Ratsun Datsun 521, now with L-20-B and a five speed


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Big battery cables built, and installed.

Front end body work started.

Combo meter repair, and pinout connections.

Headlight current fusebox bypass relay.

Rebuilt taillights installed.


I know the alternator should not put out that much current all the time, but I am only running the engine for brief periods of time. No radiator hooked up, yet.

I ran the engine briefly, without the "S" and the "L" hooked up. Did the compression test. Then hooked up the "S" and the "L" like I described, started it, watched the test light go out, indicating a charge, then put an ammeter in line, to check current output.

Edited by DanielC
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A little slow on the updates. On Tuesday, I had to do some other errands. I also have a 1974 Ford F-250 Super Cab truck, that i have been putting scrap steel in over the winter. Parts of an old riding lawnmower, a door I replaced on my Aerostar, but mainly old wire fence, and metal fence posts I have been pulling out of horse pasture. Sold 940 pounds of steel for $98.70. While I was there, my poor Ford truck saw one of its brothers being torn apart.

My plan was to stop at DMV in Gladstone, to get the title changed. Of course, there were problems. It's DMV. A minor signature issue, on the wrong line of the old title. I am working on resolving that.

I also bought some new battery cable and wiring supplies, for a positive battery cable for Ratsun Datsun, the name I have given this truck, in reference to where it came from.

While I was out with the big fun to drive 390 4 barrel Ford, I also got a ton of wood pellets for the pellet stove I use for heating, from Coastal Farm in Oregon City, and mailed some bills I made out in the morning.

I unloaded the pellets, and then took a nap.

After the nap, I started to put the battery cable together. Here is a picture of part of the new battery cable I made, along with a new wire from the alternator to the starter.



I needed to so some serious work, so I mowed some lawn after that.

In the evening, I then went to do some body work on the right front corner. Took out the headlight holder, The turn signal.

This is a picture of the cover you remove to get to the nuts that hold the front turn signal on the truck.



and here is where it was in the truck.



I also removed the side marker light.



This is a picture where the fender is "pooched" out a little from the front end of the truck hitting something.



While taking the lights off, I found sand inside the headlight bucket, and inside the back cover for the turn signal, and packed in the space between the radiator core support, and the front panel. There was also a lot of sand on top of the headlight bucket, inside the top front fender.


That was only some of the sand. There is a lot more.

It was not a case of simply unscrewing the screws that held the lights on the truck. Out of four screws holding the headlight mount on, two broke, and one had to have the head drilled off. One screw came out without breaking.

The side marker light had one bent screw, as did the front turn signal, holding the lens on the light. Both lights are rusted pretty bad, and the bulb would not come out of then without breaking the bulb.

To finish removing the front turn signal, I had to remove the cover on the inside of the fender that keeps mud away from it. One of three screws came out, one had to have the head ground off, and one I was able to remove by moving the cover, once the other two screws were removed.

Edited by DanielC
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You can't force current onto anything that isn't drawing it. An alternator only puts out the current that is asked of it, so if it's putting out 30amps that's because something (battery, a short, accessories) is drawing 30amps. You can over volt the battery, however.

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It is a 50 amp alternator. When I checked the amperage it was putting out, it was after I did a compression test on the engine. That probably drew the battery charge down a little bit. Because of that, I expected a fairly high charge rate. Because I do not have the radiator on the engine yet, I need to do some body work on the front end of the truck, I do not run it long enough to see if the current drops.

Hainz, Thanks for the link!

When I did the amp test on the alternator, my "IGN" light on the dashboard was not working. I just used a test light, between the positive battery terminal, and the "L" connection on the alternator, and in a similar fashion, used a second test lead from the battery positive to the "S" terminal.

Here is a picture of the setup I used to test the alternator.



Edited by DanielC
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most people jumper at the square connector. just make 2 jumper wires and go by the color code on engine side of the harness.


You can cut a bad volt reg and jumper it there also so it look more professional and you can go back to stock but dont go by the color codes on the volt reg as I seen them are colored wrong soemtimes.


I think this shold get your light going when you install the jumpers.



I had a Mitshibitshi alternator ones and it had a T connector ADAPTER. I dont know if this will pertain to you. But it came with a Mitshibishi rebuild once I had.


GGzilla had a drawing on how to ck a alt out put. Put I cant post photos.

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I forgot one other thing I did on Monday, April 18, 2011 (full date for my future reference)

I pulled the combo meterout of the truck to see what was wrong with it. First clue, no lights on it anywhere.

Here is a picture of the back of the meter.



First thing, what do the pins hook up to.



I had to clean the contacts on the circuit board, the contacts in the bulb holders, the bulbs themselves. Here is a picture of one of the lamp holder holes, half cleaned. I used a Scotchbright abrasive pad to clean the contacts. In this picture, one side is cleaned, the other is not.



I also had to repair some grounds on the circuit board. the circuit board does not have a full copper trace for the grounds, but uses the metal case, and rivets through the circuit board to complete the grounds. To repair the grounds, I had to bridge the head of rivet to the trace on the circuit board.



Then I had to test the combo meter.

Get a 12 volt battery, and hook the negative up to pin 10.

Apply 12 positive to pin 1, the four dash lights should turn on.

Apply 12 positive to pin 2, the left turn light should turn on.

Apply 12 positive to pin 9, the high beam light should turn on.

Apply 12 positive to pin 12, the right turn light should turn on.


Apply 12 positive to pin 7, and ground pin 4, the oil light should turn on.

Apply 12 positive to pin 7, and ground pin 8, the IGN (alt) light should turn on.


Apply 12 positive to pin 7 and ground pin 10, and also ground pin 3, the fuel gauge should go to full.

Apply 12 positive to pin 7 and ground pin 10, and also ground pin 11, the temp gauge should go to hot.


This was on April 20.

So now, I had the combo meter working, plugged it back in to the truck, and still no ING, or OIL light. I took a long piece of wire, with a spade connector on it, and plugged it into the voltage regulator plug, on the white wire, with the red stripe. I pulled the end of the wire to the hole on the dash, where the combo meter was, and found the white wire, with the red stripe, and used an ohmmeter to see if there was a connection. There was not.

Then I went under the glovebox, and looking up, I could see these connectors.



I found the connector that had the white wire, with a red stripe, unplugged it, and one side of the connector went to the combo meter plug, and the other end of the connector went to the voltage regulator plug. I plugged it back in, and rechecked the continuity from the voltage regulator plug back to the combo meter plug, and had continuity. I then jumped across the voltage regulator plug like people on Ratsun said, and I had the IGN light working.

While poking around the wiring by the fuse box, I found a short wire taped off, wiht a piece of paper in it. I pulled the paper out, and it had written on it, "oil pressure switch" I spliced a longer piece of wire to it, and hooked it up to the oil pressure switch, and the oil light on the combo meter now works.


Almost anyone who has a 521 for any length of time has had a problem with the headlight fuse, and the fuse box. There must be a reason the 510 uses two headlight fuses.

I did a "quick and dirty" easily reversible relay modification on this truck.

Here is a picture of an extra in line fuse holder I added to the fuse box,



The end of the orange wire hanging off in space will go to this extra blue relay, pin 30.



And here is another picture.



This extra relay is hooked up as follows.

Pin 30 gets power from the the added fuse.

Pin 87 goes to the terminal on the stock headlight relay that has the red wire with the yellow stripe on it, with a short jumper.

The red wire with the yellow stripe goes to pin 86 on the new relay

A short wire to ground goes to pin 85 on the new relay.


This additional relay takes headlight power out of the stock 521 fuse box. The headlight power also has to go through some connectors, the headlight switch, and into the cab, and back.

This is the voltage drop in the headlight positive side before the relay was added.



And this is the voltage drop after the additional relay.



After playing with electrical, I decided to remove three broken studs off the bottom of the old exhaust manifold.

Just your basic cut off the broken stud flat, centerpunch it, and drill it out. Then chase the threads with a thread chase tap.

No before picture, but here is the manifold ready for new studs.



Edited by DanielC
Photobucket shenaganians
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looking good, wish I could have been able to do something with the 521's I had. I gave the first one away because I thought I'd never find another one. So I got rid of it and less than a year later I got another one. I sat on that for a few years and never found enough parts to put it together so I traded it for a 620.

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I'm well on my way of having to buy more bolts. I am learning the fine art of drilling out broked bolts, and screws, and retapping the holes.

It is also good a 521 uses SAE standard American threads for the body bolts. I am also getting good use out of taps my father had.

Here is my general procedure for removing bolts. Wirebrush any exposed threads on the end of the bolt if possible. Spray penetrating oil on it, and let it sit. Try to remove the bolt. it it starts to turn, and then gets difficult to turn again, spray more penetrating oil, behind the head of the bolt, and screw it back in.

If I can, I use this electrolysis process to try to eliminate the rust first.


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Guest kamakazi620

I'm well on my way of having to buy more bolts. I am learning the fine art of drilling out broked bolts, and screws, and retapping the holes.

It is also good a 521 uses SAE standard American threads for the body bolts. I am also getting good use out of taps my father had.

Here is my general procedure for removing bolts. Wirebrush any exposed threads on the end of the bolt if possible. Spray penetrating oil on it, and let it sit. Try to remove the bolt. it it starts to turn, and then gets difficult to turn again, spray more penetrating oil, behind the head of the bolt, and screw it back in.

If I can, I use this electrolysis process to try to eliminate the rust first.


Damn Mang!!!!! way to put in work!!! don't forget about discount import parts or baxters for datto parts if you go to baxters tell them to put it on the northwest Z account for a discount

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Thanks for the tip on NW Z cars. I Think I still am current with Datsuns NW. Need to find out, and get my card.

I have been working on the little lights, the headlights seem to be working good, since I added the relay. See post I made in this thread, April 21.

The taillights. They looked like this.
Left side. Notice the fiberglass holding the turn signal lens.

Right side. Look closely above the last "9" on the license plate, and you will see the remains of a bracket that held a socket for trailer electrical. Luckily all the trailer wiring was done on the taillight harness, and not on the harness for the truck. But it was a mess.

The back up lights did not work in either taillight assembly, and the turn signal bulb in one was a low watt incorrect bulb, for the turn signal.

The left side taillight was held on with bolts and nuts in all four corners. It came off the truck easy. The right side, not so much. The two inside screws, had nuts on the back, and I was able to hold the head of the screw with a pair of vice grips, and turn the nut off with a wrench, after an overnight soak with penetrating oil. The lower screw on the outside, same idea, but the screw broke. The top screw on the outside, screwed into a welded on nut on the bed. That screw had to have the head of the screw drilled off, and then the remaining screw parts drilled out, and then chase the threaded hole with a tap. (size, 10-32)

A while back, I did a write up on repairing 521 taillights. That write up is here:


Now, the fun part. Go grab a right and left taillight from my stash of 521 parts, and bolt them on.

left side,

Right side.
The taillights were tested on the bench, before I put them on. The fuse box is currently out of the truck, so I haven't tested them on the truck, yet.

Next up, the side marker lights. The left rear one was gone. The other three did not work.
Unfortunately, I do not have a stock of clean, working ready to go marker lights. I do have some parts, but nothing complete.
I am having to clean rust off the ones that were on the truck.

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On this page.

Front end body work.

Park lamp cleaning.

Bed rack removal.

Taillight ground issues.

Front wheel selection.



I also worked on the front park, and turn signal lights. Here is a picture of the left side. In spite of the body damage on this side, the amber lens has only one small crack in it. Very usable, dirty, but usable.

And here is the picture of the right side. It is dirty too.

First, clean the lens.

And the trim.

Here is the lens and trim ready to use. Well, one lens anyway. I also had some park and turn signal metal bases, that were derusted, by electrolysis, lightly sandblasted, primered, and painted. The back side, I painted black. I had some black Dupont Centari i used. For the front, I used some "rattle can" fake chrome paint. Also, I had some already clean gaskets.

Left side,

Right side. I am missing a welded on bolt on the right side of this base.

So I took the previously cleaned and painted bases, and put the just cleaned lens and trim on the bases, with the screws. I used this grease, just a little, so it will come apart the next time.

I tested the lights. Here is a park lamp test

And a turn signal test.

I also tested the left side in the same manner

I then put the mounting nuts on the turn signals.

And here are the turn signals ready to go on the truck.

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This is how I am cleaning the side marker light bases for the truck. There is also an old battery hold down half submerged in the soup.


Here is my "electrolysis soup"



The soup is using about 3 amps of current.



I also went through my stash of old air cleaners. Inside one, I found this.


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On April 25, I did some work not really picture worthy. Just making a parts list, cleaning some parts for side marker lights, put the radiator and heater back in the truck. I did get the heater water valve turning again.

Soon I will do a write up on Datsun side marker lights. A lot of different Datsuns use the same parts in the marker light, the only difference between different Datsun Models is the rubber base, and the length of the wires.

I also need some new screws for the fuse box. I may also research to remove the fusebox switched power from the ignition switch, to a relay.

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Not all the work in getting a truck running again is glorious photo worthy work. such was today, again. This truck has no master cylinders, that work in it. The clutch slave cylinder is rusted solid. I grabbed a clutch slave from another 521 I have, it is unusable too, I think. I also have a broken emergency brake cable.


I am a member of Datsuns Northwest, at least I think I am current. I sent a E-mail to them, to find out my current membership status. I need this, because of the discounts on needed parts. I started to look up some part numbers, using this website.



Also I am working on some issues with the title change.


Since I need a brake master cylinder, (and possibly brakes) I contacted MKlotz about disk braking this truck, and the master cylinder I will need to do that upgrade.


Finally, time for a parts run. Clackamas Auto, the obligatory new fuses, and a thermostat, and new lamps for the side marker lights. Little screws for the fuse box, no luck. Next stop, Coastal Farm, buy a 1/16 to 3/8 drill bit set, there are more bolts to drill out. Also bought a few extra smaller bits, the ones that break easily.


Then I got gas in my Aerostar, my daily driver, and that was only $68.00. Some other errands, and back home.


Still need brass #8-32 screws for the fuse box. I called Oregon Bolt. They can get them, but it will be a few days. Called Parkrose Hardware, they have them, but they are in Parkrose, in Northeast Portland, a pretty long way to drive, at $3.779 a gallon. Next, on a lark, I called a local ACE hardware, in Lake Oswego, and they have the brass screws. I drive down there, and get them.


I got home. I put the fuse box back together. I put some older used antifreeze in the radiator, and start the engine. It starts easily, but it is not idling OK, it wants to die if i let it go below about 1200 RPM. While it is running, it is also a little "rattly" in the front of the engine. I need to check the timing chain.


I still have no lights on the front of the truck, but I check the taillights. Taillights, check. Turn signals, (emergency flashers, actually, check. Back up lights, no. (did I forget to reconnect the reverse light switch on the transmission when I put it back in?) The brake lights, I check by just jumping the two wires going to the brake light switch. Right one is bright, the left, not. Other lights on the left side are glowing dimly. Need to check the ground on the taillights. Right side rear marker light works, the left side does not.


The heater fan runs. The windshield wipers do not. The temp gauge reads really hot, even though the engine is not.


And that is where I am tonight on this truck.

Edited by DanielC
change carparts manual link to one that works
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YEA, Pictures!

This is the rack that is on my truck.


I do not really want it, but MicroMachienery has said he would like it. If he ends up not wanting it, it may become available.


It was bolted on to the top of the bed using 6 3/8 bolts on each side. How they got the nuts for the bolts under the lip of the bed, I do not know, but they were rusted, and could not be unscrewed. To remove them, I had to drill the head off each bolt.

I used these drill bits.


This drill bit set was less than $17.00, and worked really good.

I centerpunched the bolt head, in the center. No picture, maybe later,

I use old motor oil for lubricant when drilling metal.

I used the 1/8 drill to make a pilot hole, in a corded electric drill.

Then I drilled the bolt head with a 3/8 drill to remove the head.

Here is what remains of the bolts, from one side.


and here is a picture of the bolts gone from the rack, and the rack just sitting on the truck.


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If you get reverse drill bit set, it sometimes makes life waaaaaay easier....


Left hand drill bits work good on screws and bolts into tapped material.

On his there were nuts so there would have been no advantage to the more expensive l/h bits.

The idea is that the bits will grab and in most cases un-thread the fastener.


I'm kind of partial to the rack.

I'm going to build one for my truck as I'm going for a "shop truck" look complete with door logo.

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The problem is I could not get a wrench on the nut, buried under the lip of the bed. When the bolts were new, the nut could be lightly held, until the threads on the bolt caught it, and it did not need much torque to tighten, or unscrew.

After ten or twenty years of rust on the bolts, you need to hold the nut firmly to unscrew the bolt out of it.

I could turn the bolt and the nut would just spin with the bolt.

I could only get the tips of an open ended wrench on the nut, barely. I could not hold the nut firmly enough to get it loose.


The rack is just EMT tubing, and two "L" channels of steel sitting on the bed. There are adapters to go from a standard pipe thread, to a compression fitting on the EMT tubing.

There is flat steel going lengthwise to tie the EMT crossbows together.

I will go and take some more pictures of the rack construction details.

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