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Datsun 510 temp wiring issues


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   Trying to figure out how to get my stock temp gauge to work with a SR20DE swap. I pictured what I am looking at because I was told the body harness has a yellow/white wire to connect to make the temp gauge work. Pic(1) is the new wiring from the engine harness labeled for temp. pic (2) is the interior harness plugs next to the passenger kick panel that have a yellow/white wire which i was told is the temp wire. pic(3) is a mystery to me but looks modified in some way and is my second question. 


The driver side headlights dont work and the passenger seems to be stuck on high beams. All the other lights seem to function fine but the driver side does not come on and does not react to the high beam. The bulbs are appear to be good but the high beam stuck on seems to be a problem too. Pic(3) shows the modified plug that might be associated but not sure. Owner (frank  out of Everett) claims the headlights worked before he sold it but they do not now. Not sure if the link to the picture works but I included it here. 


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Pull the headlight switch out to the first position.... do the parking lights come on? You have to have parking lights to work the hi/lo headlight relay otherwise the default off position is in the hi position.



There are two fuses (both 10 amp) one for each side. Find the fuse with the Red/Blue stripe. There will be a Red wire beside it for the passenger side lamps. Never trust a glass fuse by looks, use a meter or swap a different fuse in to see if they come on.


Temp gauge. To confirm, ground the Yellow/White stripe wire and gauge should move to the full hot position. If it doesn't... does the gas gauge work??

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Datzenmike: The guage is unknown because I bought the car this way and the previous owner isn't the friendly helpful type. So I see a wire off the engine harness that I believe Ray Stonehawker wired with a yellow wire tagged as temp to cluster....and I located the pictured yellow/white wire off the interior body harness that I was told does the temp. So do I splice the body harness wire and ground it to see if it pegs out? or do I try to connect both yellow wires and just see... keep in mind this a SR20 swap so thats why I need to wire this stuff. Gas Gauge seems to work its not on empty like quarter full on gauge. 


as for the headlight I just checked parking lights as you suggested and yes parking lights come on with first click

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2edeye: I am more concerned with trying to get this temp gauge working because The Wallflowers once said; "You can drive it home...with one headlight"   haha but I appreciate all the help and those that see this post. 

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1 hour ago, Skoob said:

and the gas gauge seems to work its not on empty


This is good as both temp and gas gauges are powered from the same source.


2 hours ago, datzenmike said:



Temp gauge. To confirm, ground the Yellow/White stripe wire and gauge should move to the full hot position. If it doesn't... does the gas gauge work??


This will confirm you do have the temp wire. Try grounding the Yellow wire and if it's connected to the Yellow/White wire you're good.

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So i grounded the yellow/white wire (on the interior harness) and it pegged all the way hot...so I unhooked it and wired the yellow wire that was labeled "temp to dash" directly to the Yellow/White wire and started the motor. I let it run for about 5 minutes (it seemed) and the needle never moved. Since I was scared the motor was secretly over heating I backed off and turned it off.  I re-tested the yellow/white to the chassis and sure enough it pegged all the way hot showing the factory gauge works. 


So now I am wondering if the car sitting there idling for about 5 minutes really doesn't move the needle and I should trust it works? I have a hard time with that because a simple over heat means the motor has to come apart so I am cautious with this mainly since I didn't do anything to the car till now. Hard to say what's really been done to it. I appreciate all the help and curious what the next step should be? Soon as I get my fans here I should be able to test drive it but won't if I don't know the temp. I fear I probably will need to buy an aftermarket gauge just to be double sure or what do you guys think? 


Also: The left headlight doesn't work but the right side is stuck on high beams no matter what I do which seems wire related to me but not sure. My parking lights work, brake lights and turn signals but No driver headlight or High beam at all on drivers side. Not sure how to trouble shoot it without just re-wiring it. I posted a pic with the odd connector jumped near the fuse panel. The headlights arent as important as the temp gauge but still want to figure that out too. Any direction helps and maybe I need to just run the car longer but since I have no idea where this motor came from or it's internals/thermostat etc i want to be safe. 


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Did you ground the yellow wire to test your connection to the yellow/white wire?


What sender are you using for the engine? I don't know if an SR is compatible with an older 510 gauge or not.


Leave the rad cap off next time. With it open the hottest it can get is boiling.... and you will visually know it.  Five min isn't enough to overheat it so don't worry about it.



Do the side marker, parking, dash and/or license lights come on??????? The head light relay won't switch between hi/lo without them on.



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I am not sure the sender name but the yellow wire that was labeled by Ray Stonehocker (who wired it before my ownership) has a yellow wire off the engine harness that is labelled "temp to dash" on it towards the lower passenger side of the engine bay.  I grounded the interior yellow/white wire near the kick panel to verify the gauge actually worked and it did. Next to connected the yellow labeled temp wire to that same yellow/white wire and ran the car for about 5 mins. Because I didn't see the needle move at all (the garage area is unheated if that matters) and when I did not see the temp needle move I shut it off to verify connections. maybe I need to run it longer with the cap off as you suggested as I did not visually see anything overheating on it but I was worried about internal gaskets. 


Hmm, that's a  good question on the headlights because I noticed the parking lights and 1 side marker DO come on on first click. No dash lights at all maybe bulbs. I also do not remember seeing the license plate lights on but that could be due to no bulbs in there... The headlight is very puzzling and thank you for helping try to figure all of this out, I haven't had to hop on a car forum in many moons. 

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If you connected the yellow to the yellow/white then ground the yellow with the key on to confirm that they do connect. Already said this



1 hour ago, datzenmike said:

Did you ground the yellow wire to test your connection to the yellow/white wire?


Maybe labeled wrong. Maybe more than one yellow?

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Yea, or it's really just that cold on the temp gauge from idling? However after 15 minutes I feel it still should have registered even slightly ? I ordered an aftermarket gauge to run side by side and say F the bs.... 


As for the last little annoyance of the headlight issue. I jiggled the silver relay and pressed the wires around and I did see the right side flicker once but didn;t see too much activity from that thing to know if it's a cause. The high Beam being stuck on is my main concern since that would have to mean either the HB switch is bad Or some type of odd ball alien wiring issue is making it stick on. I checked the areas where the sockets plug in and they are fine untouched, no fuses appear to be blown anywhere and all wiring appears to be connected correctly. Yet, as soon as I pull the headlight switch all the way out the passenger side only comes on with the high beam stuck on & no reaction to the high beam column lever switch as if the high beams were running on the same low beam circuit. If the high beam wasn't stuck on I would diagnose the very simple things like headlight bulbs and such but the high beam being stuck on seems very unique and not sure where to look. Anyway, just frustrating that the person who sold this car acted like he was this cool Datsun 510 guru yet pulled the Chris Farley in "Tommy Boy" scene where he rips his door off and is like "waddddaya dooo?" haha this dude who sold this 510 to me was the mr cool guy until I paid for the car. Just comical because i'm still the happy/proud owner of a 68' 510 with one of it's eyes punched out. Gas tank is half full.  I just ate a gnarly edible. 

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Need S13 temp sender (single wire temp sensor) to make the stock gauge work.  Different resistance than the S14/15.  Easy 10 dollar fix. 


I would check voltage at headlights.  If only the outside headlights are on it's low beam.  One is probably just running on less voltage bad ground or bad connection on the power side.

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46 minutes ago, banzai510(hainz) said:

clean the relay and reseat the connector or best yet ck and clean the 2 fuses in the fuse box or


the light wiring wasn't changed I hop as it didn't need to be changed with a SR install

If a H4 harness was installed then that could be a corrosion issue also


The wiring wasn't changed but Frank and Atom wired that car when it had a KA-T and then that was pulled and the NA SR was put in it.  

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]2eDeYe:  Ohhh helll yeaaa! (Steve Austin voice) 


Icehouse: ok that makes much more sense why I am not getting any temp reading. Is this S13 an Orielly's thing I can get on the spot and if so what motor do I look under? Also seems you know exactly what car I am working on which is a relief. I'm glad someone knows some history on it as I feel in the dark the way the deal went down. I know about the previous K swap and that it was removed for this Sr20de and supposedly wired by Ray Stonehock who claims I can wire straight to the yellow/white and make the stock temp work but guess not. $10 is a huge relief.


banzai510(hainz): The headlight could need some cleaning the relay looks to be the silver one with 4 wires to it and looks to be semi tampered with. Frank said the headlights worked the whole time and just was puzzled when I asked him but I already had the car so what could I do. I will try to clean that relay like you mentioned and see but I really just don't get how the high beams on one single side would be stuck on with a sticky relay?  





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I have never cleaned a relay myself but a buddy of mine I told him   when his lights only worked on HIGHbeams that it was the relay. I put a spare I had and it worked. I wanted 100 for the relay so he learned to fix it himself(Ok IM lying on this one)  but its a good incentive to learn when one gives such a price.


just make sure the lamps work in the first place!!!!Duh.. had this happen also  both lamps. so i don't think whats the chance both are just bad!!!!! Yes it happened.

clean fuse connection,. and ck the fuse. sometime pulling the connector on the fuse box the white connector might be it also. Corrossion.

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using a test light

when the front lights are OFF


going from chassis ground and probe the 3 tangs on back of lamp will be 12volts  on ALL 3 tangs(tabs however you want to call it)  This means pwer is making it to the lamps.

then when you pull the switch out one the parking lamps come On then pull all the way out the lights should come one, what happens is ONE of the tangs will go to ground and youll get no voltage but the other 2 you will.  This happens thru the RELAY!!!! switches a ground to the spot it needs to go. Most time the arching on the contacts causes a high resisitance and thus bad


highbemas is same 12volts on Both then when you put to high one will ground

Edited by banzai510(hainz)
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icehouse: yea, he was cool until the deal was done. Then he had amnesia for even the most basic of questions but the forums seem like a better route for this stuff. I will go get a volt metter from the auto parts store and see what they are putting out. What voltage are they suppose to be at ? Also, what year motor is this and what cars come with my motor? He also said it has a JDM trans & posi rear end but not sure how to confirm. 


Banzai510 : I was going to try your method too and open up that silver relay and see if I can clean it up just in case thats all it is.


Lockleaf: Just went and grabbed the 240sx sender...now where oh where is the sender on the motor? I assume its on the back in some dark hard to reach spot? 

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Also: I just checked and the coolant temp sensor on the motor IS a one wire/ solid yellow which appears to be the one I used up to the body harness. The gauge I verified works and the wires are connected. So the only thing is maybe its really just not hot enough to register but everything is hooked up. 

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banzai510: I assume I will need a new relay regardless because I tried to clean it up a bit and check connections. I seem to be getting 9volts roughly across all of the headlight sockets so I assume power is making it to the sockets. Yet the driver side doesn't come on and the high beams stuck on...wouldn't that only leave the relay if the connections are good?


as the Temp sensor saga continues I see that my current sensor has one yellow wire that seems to match the yellow wire labeled "temp to dash" by known Datsun 510 mechanic/ray so I assume labelling was already accurate. I verified the wire I was connecting it to inside was grounded and verified by the stock temp gauging peg'ing out to full hot when grounded. So After that I made the connection on the two wires. yet after 15 minutes of running and using a infrared heat gauge I witnessed the engine block heating to 140/150 degrees and no movement on the stock gauge needle so I cut it off. I currently haven't wired up a fan yet so I was worried to test this temp gauge problem. I ordered an aftermarket one but in the meantime I wanted to try and figure out the temp wires. 

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