521 wiring problems

[sick620]

I was driving the 521 and battery fell into engine bay because I forgot to secure it. Positive arched out on brake line. Other that the fried brake line the extent of the known damage is: fried ground wire running from alternator, and fried throttle cable that acted as a ground. I installed some new ground straps in a few places, replaced all fuses with new, and cleaned up the fuse box… Now we are getting no accessory power and intermittent power to the starter… any ideas on anything else that could have been fried?… 1st matter of business is replacing the ghetto push button start I had wired in with a toggle switch, can someone tell me the proper order of wires on this aftermarket toggle switch?

[banzai510(hainz)]

I learned my lesson and always secure the battery from now on.This is a common Datsun owner trait.This happen to me with my Toyota. which had the hold down but was loose and over time battery slid to and hit positive.

 

Good Luck  you still can get 521 switches then use the wire diagram. otherwise this might soon becoming a Parts Vehicle

Edited June 7, 2023 by banzai510(hainz)

[datzenmike]

When I was 25 and knew everything I welded the throttle cable twice!!!!!!!!! from the battery falling over. I changed all my resumes after that to 'slow learner'.

[sick620]

6 hours ago, banzai510(hainz) said:

I learned my lesson and always secure the battery from now on.This is a common Datsun owner trait.This happen to me with my Toyota. which had the hold down but was loose and over time battery slid to and hit positive.

 

Good Luck  you still can get 521 switches then use the wire diagram. otherwise this might soon becoming a Parts Vehicle

Oh god I doubt it’s that bad worst case I just need to take the wrap off all the wires and pull out the dash and inspect everything until I figure it out. I was just hoping  someone knew of some common failure points… the ground wire that runs off the alternator I am pretty sure gos to the voltage regulator, that is not a necessary configuration correct? Like as long as the engine, frame, negative of battery, and voltage regulator are grounded to each other it does not necessarily matter where the alternator is grounded to right? I can just ground it right to the frame? 

[banzai510(hainz)]

be honestI dont know. I just notice this small black wire grounds the alternator and that it(I find strange)  causer the motor seems pretty much Isolated thats why it finds the ground thru the throttle cable.  you think there would be a body ground to the engine block

 

Whne My Toyoya positive grounded to when thru the emergency brake cable and cook the isulation off and weakened the cable till it busted when I did one pull.

[sick620]

Ok I fixed the issues. The wire that fried that grounds the alternator fried all of the grounds in the harness and some were not connected anymore. I re wired the grounds now I have power and truck seems like it’s going to be fine. I am trying to wire up some aftermarket tail lights now, I have everything working but brake lights… is the power at the brake pedal supposed to be constant or only when ignition switch is on? I’m not showing any power at the brake pedal for some reason. 

[banzai510(hainz)]

power is on all the time to the rear,see brake pedal switch.  ground your test light and ck both side to see if one side is hot.

 

check at the switch under the pedal and see if one side has 12volts.If not then work your way to the fuse box.

See if the horn works.I cant remeber is they share the samefuse or the istrument panel.

[sick620]

OK, so I tested the power to the brake switch at the pedal and there was no power to either side of it at all.

 

All of my fuses have power on either side of them testing them with my meter. I tried jiggling all the wires, making sure they were tight and making a good connection at the fuse box.

 

So the issue Had to be between the fuse box and the switch-I decided to try to test it by running my own hot wire from the battery straight to the switch.

 

I wasn’t sure what wire at the switch is the one that runs to the brake lights but when I hook up my hot wire to one side and one of the wires to the other side, it clicks a relay then also when I press the brake pedal it clicks that relay off and on. I’m assuming that is the correct wire. It’s kind of weird though because it seems like the relay gets power when the two wires are connected without even pressing the break pedal and then when I press the brake pedal, it’s like it disrupts the current to the relay but maybe this is how it is intended to operate? When I hook up my tail lights, I still don’t get brake lights, even when it is wired up in this fashion, and I can hear the relay clicking when I press the pedal. 
 

maybe there is supposed to be something grounded at the back of the truck where the tail lights are that isn’t anymore? 
 

now I’m considering running a wire from that relay whichever one makes 12v when the pedal is pressed back to the brake lights, and connecting my temporary power to brake switch wire permanently to the fuse box as my own permanent bypass.. 
 

 

[banzai510(hainz)]

IM not that familiar with the circut .I just know that one side hase 12volts. If no 12volts then check towards the fuse box by ohming out the wires. Find the color and try to go to the fuse box. I do not know after that. I think the early 520s/521 had a  wire on the brake distribution brake line if I remember right.  on fire wall by the passenger side

 

Mine is late 71 listed as a 72. it dont have this wire brake distribution

Edited June 21, 2023 by banzai510(hainz)

[Crashtd420]

I could be wrong I dont ever remember having a relay for the brake lights....

I went through my whole harness on a table before reinstalling....

The 521 should just be power to the pedal switch then out to the brake lights.... 

[banzai510(hainz)]

 

 

about 1.30mins in youll see a switch from the early trucks on fire wall pass side

[Crashtd420]

2 hours ago, banzai510(hainz) said:

 

 

about 1.30mins in youll see a switch from the early trucks on fire wall pass side

I think the wiring is still the same... 

I looked at a couple wiring schematics and it's the same wires but show the switch in a different location ....

My guess is the relay was an add on by the previous owner to lessen the power load through the switch....

[sick620]

2 hours ago, Crashtd420 said:

I think the wiring is still the same... 

I looked at a couple wiring schematics and it's the same wires but show the switch in a different location ....

My guess is the relay was an add on by the previous owner to lessen the power load through the switch....

I dont beleive so. The relay that is making the noise is VERY factory looking. It looks just like the voltage regulator and the other couple small ralays. Ill upload a pic tomorrow.. 

[sick620]

Here is the relay I am hearing. It is the light relay I am pretty sure looking at wiring diagram. Weird that when I hook up one of the wires at pedal and my own 12v power to the pedal it makes noise. Everything else in the truck is working Light related. I am leaning on just wiring my 12v power permanently and running my own wire from Pedal back to the brake lights… this has me a little worried that something still isn’t right. But with everything functional I don’t want to mess with it too much more… maybe i should look under the truck and see if anything is fried underneath because that’s the only place I have not checked yet. 
 

[Crashtd420]

12 hours ago, sick620 said:

I dont beleive so. The relay that is making the noise is VERY factory looking. It looks just like the voltage regulator and the other couple small ralays. Ill upload a pic tomorrow.. 

That definitely looks like a factory relay....

I couldn't find one for the brakes on a diagram....

 

What are the wire colors at the switch?

I can go out and check mine for comparison....

[datzenmike]

That's probably the horn relay.

 

The brake lights are most likely on a fuse that has other things on them such as, but not necessarily, the interior light, horn, any lighting, hazard flasher, clock. These are all things that don't need the ignition on. When you add power to the brake light you are also powering anything else on that fuse.

[Crashtd420]

41 minutes ago, datzenmike said:

That's probably the horn relay.

 

The brake lights are most likely on a fuse that has other things on them such as, but not necessarily, the interior light, horn, any lighting, hazard flasher, clock. These are all things that don't need the ignition on. When you add power to the brake light you are also powering anything else on that fuse.

I was just thinking this same thing about possibly back feeding power to a relay but mike beat me to it..... 

 

So if jumping power to one wire makes the relays click does jumping power to the other wire make the brake lights come on? 

 

Also how are the grounds for the brake lights? 

Have you checked to see if power or ground make it to the actual light  socket ?

[datzenmike]

Does the horn work? Bet anything it's NOT working

Does the 4 way emergency flasher work? Bet it's not either.

 

Replace the 15 amp fuse on the far right end of the fuse box.

 

If the headlamps work or the interior light then the fusible link is OK.

If the above do not work and the ignition switch does not turn the wipers or heater fan on then probably the fusible link is blown.

 

[banzai510(hainz)]

521 fuses dont trust them and clean fuse box ends

[sick620]

Horn does work. 

When I put power to the other wire by the pedal nothing happens at the brake lights. 

According to the wiring diagram the wire that is supposed to feed power to the pedal switch is on the same circuit/fuse as the horn. So I am possibly giving the horn relay power. but that's weird because the horn already works and has power. 

The 521 fuse box was cleaned of corrosion and brand new screws and fuses installed. And my multimeter shows power on both sides of all the constant powered fuses, and power of all the ignition ran fuses when igntion is on, I checked to make sure wires are in correct spots and wiggled them all around to make sure they are making good contact at the fuse box, I never tried hazards, but otherwise have power to everything else I am pretty sure. Ill check hazards tomorrow. 

[banzai510(hainz)]

well ohm out the wire under brake switch to the fuse box and youll find the proplem

but like I said I dont have a early 521 with the switch on the hydraulic distribution on fire wall so Im at a loss of truely how this works

Edited June 23, 2023 by banzai510(hainz)

[sick620]

Ok so I ran a hot wire to the pedal, then a wire out to the brake lights. There must be something wrong with the switch because not pressing pedal we have brake lights and when you press it in the turn off lol….

 

also everything else electrical has been tested and is working. Hazard lights included. Truck starts and runs finally. 
 

i guess ill try replacing pedal switch .

[datzenmike]

Wrong switch? When the pedal comes up it depresses the plunger on the switch and opens the circuit. When pedal depressed the plunger on the switch comes out and connects the circuit and brake lights come on. 

[banzai510(hainz)]

ohm it out I figured that was already done when cheacking this out

[sick620]

5 hours ago, datzenmike said:

Wrong switch? When the pedal comes up it depresses the plunger on the switch and opens the circuit. When pedal depressed the plunger on the switch comes out and connects the circuit and brake lights come on. 

yeah maybe the wrong switch. It is the one that came in truck and I thought I recalled the lights working at some point but maybe not. Or maybe somehow when I fried everything it got messed up inside IDK.. Im going to just pull the known good working one off the b210 and try it in place. Now that I have ran my own wiring I am just going to run it all off my wiring. I am not going to ohm out anything.