PNW 720 97499 Posted January 17, 2019 Report Share Posted January 17, 2019 New to the world of Nissan/Datsun (not Nissan, I just sold my '91 Sentra, owned an '04 SE-R Spec-V). Purchased this 720 this week knowing some of the quibbles going on with it. Just would like some advice with electrical demons. Here are my issues and how I'm looking at resolving them, by order of importance: 1: Left turn signal stays lit, no flashing. I've gone through these forums and have tried messing with the 4-way to see if it was an issue. Right blinks just fine, 4-ways work fine. Left front signal is in-op at the moment, a new unit will be here Friday to put on it. When I turn the left signal on, i can hear the flasher, but not the typical sound. It sounds more like a light bulb which just popped its filament, coming from under the dash (where the flasher is). Barring the new left front light resolving my issues after replacing the flasher as well, any ideas as to what this may be? 2: Fuel, tach and temp gauges not working. Read in the forums here to clean the contacts, will be performed this weekend. 3: Radio wiring in-op. I've gone through the fusing a little bit, was completely missing the brake light fuse despite there being a spare in the fuse box... 4: Dome light. Any ideas where I can get the whole assembly? Junkyard? This forum has been a great help so far in what I'm needing to do to get this Datsun's issues resolved. 1 Quote Link to comment
AtomChurch Posted January 17, 2019 Report Share Posted January 17, 2019 Sounds like a grounding issue to me. Clean all the grounds in your harness. The flasher "unit" has three prongs and works the same with both sides. Left and right. So you have a short, or rather power feeding the wrong way somewhere else looking for a ground. No "visible draw" to click the flasher unit. I do not mess around with a lot of 720's, so someone else might know of a common problem. 2 Quote Link to comment
datzenmike Posted January 17, 2019 Report Share Posted January 17, 2019 1/ either the front or rear left side turn bulb is burned out or corroded in the socket or loose. With not enough load from two bulbs so the flasher unit just turns on and does nothing. The turn indicator also just stays on. 2/ try replacing the #4 fuse from the left hand side.. 2 Quote Link to comment
AtomChurch Posted January 17, 2019 Report Share Posted January 17, 2019 What mike said for sure. The gauges are ground based. I have temporarily fixed a fuel gauge, for example, by connecting an alligator clip to the dash (negative) side of the battery and then to the fuel tank itself. Essentially "fabricobbling" the ground the tank should have had. You can test the sending unit the same way, but shorting the single wire to ground and seeing if your gauge for fuel reads full. 1 Quote Link to comment
datzenmike Posted January 17, 2019 Report Share Posted January 17, 2019 Fuse #4 feeds the tach and the voltage regulator that feeds the two gauges. Hey Atom!! 2 Quote Link to comment
PNW 720 97499 Posted January 19, 2019 Author Report Share Posted January 19, 2019 Fuses are all good, so that's not my issue. I pulled the dash and cleaned the contacts off, used my voltmeter to ensure power was flowing through the wiring, but I haven't checked resistance. Put back together and the gauges don't work. I haven't messed with the stereo yet, as I still need to decide which head unit I want. But I did remove a home-brew wiring setup they had put in. Left blinker works after replacing the front blinker/parking light assembly. Found the dome light assembly in the cab of the truck, now just need to figure out the light bulb and hardware to reinstall it. 1 Quote Link to comment
PNW 720 97499 Posted January 24, 2019 Author Report Share Posted January 24, 2019 Quick question: which wires from the dash plugs are my grounds? If not known, I'll chase the ground down. 1 Quote Link to comment
datzenmike Posted January 24, 2019 Report Share Posted January 24, 2019 Black wires are ground. On the White 10 pin connector. 1 Quote Link to comment
PNW 720 97499 Posted January 24, 2019 Author Report Share Posted January 24, 2019 Thank you! Know of anywhere in the PNW with 720 body parts? Looking for a passenger side door 2 Quote Link to comment
wayno Posted January 24, 2019 Report Share Posted January 24, 2019 It appears that there are 2 1985 Nissan 720 trucks in the Vancouver WA pick and pull(wrecking yard) right now. The 720 wiring harness is weird, the grounds it has are important, but you cannot start adding your own grounds as it can mess stuff up. The only way you can say you checked all the fuses is to take each one out and test it with a volt meter, they can look fine but not work, I have thrown away more than one fuse that looked good but was not good. My 1982 Datsun 720 diesel instrument cluster has 2 grounds, one for the left/right turn signals, and the other one for the clock, I expect that the gas trucks could have another one for the tach, there are very few grounds in these dashes, most everything has 2 different colored wires other than black, the grounds for all these instruments in the cluster are somewhere else, the whole thing is made of plastic. 1 Quote Link to comment
PNW 720 97499 Posted January 24, 2019 Author Report Share Posted January 24, 2019 Thank you for the info! This truck has some sheisty wiring for sure. I’ve gone through quite a bit of awful work and keep finding more and more things done worse than shadetree. Do you by chance know the colors of the vehicles in Vancouver? Not the most important as I plan on painting the truck in the future anyhow. 1 Quote Link to comment
wayno Posted January 24, 2019 Report Share Posted January 24, 2019 I do not know why but I thought you were local(Portland area), sorry about that. Both are multi-colored, one appears to be dark blue body with white hood, the other one is also a dark color with a silver looking hood, just search the pick and pull inventory from zip code 98683 and click on 50 miles, search "Datsun pickup" and "Nissan pickup", you will see the photos of the trucks in the Vancouver yard. 1 Quote Link to comment
Charlie69 Posted January 24, 2019 Report Share Posted January 24, 2019 (edited) I have pulled many 720 harnesses and it takes time and patience but can be done without cutting any wires. The engine compartment wiring passes through the firewall into the cab with the dash pulled. Edited February 3, 2019 by Charlie69 1 Quote Link to comment
datzenmike Posted January 24, 2019 Report Share Posted January 24, 2019 Agree totally with the above. It can be done 1 Quote Link to comment
PNW 720 97499 Posted February 3, 2019 Author Report Share Posted February 3, 2019 So I have resistance through my wiring, however I'm not sure what my numbers should be. I haven't chased the ground wire down, as I don't want to pull apart the harness. I pulled a useless ground off the battery negative to a body screw: again, shiesty wiring. Fairly confident it is not the fuse. I pulled the 20A for the gauges, put back in and I got the dash beeping at me; plus, the dash lights work. Any ideas which specific wires I should be checking in the three connectors? What should the resistance or voltages be reading? Is the Haynes manual worth it? Positive note: local wrecking yard had a 720 king cab and the door I was looking for in the same color. 1 Quote Link to comment
datzenmike Posted February 3, 2019 Report Share Posted February 3, 2019 There is a collective ground in the cab somewhere above where the air conditioner would be. All grounds are black. It will be bolted to the sheet metal. The ground is totally useless now if disconnected. Make a new one and screw down securely as the body MUST have a ground to the negative side of the battery. 1 Quote Link to comment
PNW 720 97499 Posted February 3, 2019 Author Report Share Posted February 3, 2019 Truck started and ran just fine without the shady 16 gauge wire from the battery to the body, about 4". That small of a wire I can't think be a great ground conduit. Correct me if I'm wrong though. I'll have to look further into the collective ground behind the Vent controls (No AC) tomorrow. 1 Quote Link to comment
datzenmike Posted February 3, 2019 Report Share Posted February 3, 2019 16 is no good. Get anything around 10 or maybe 12 and ground the body. You can even run something from the block to the firewall if you want. 1 Quote Link to comment
Jon's AD3 720 Posted February 17, 2019 Report Share Posted February 17, 2019 On 1/23/2019 at 8:53 PM, PNW 720 97499 said: Thank you! Know of anywhere in the PNW with 720 body parts? Looking for a passenger side door i have three potential parts trucks north of seattle. 84/85 720 4x4 1 Quote Link to comment
PNW 720 97499 Posted February 17, 2019 Author Report Share Posted February 17, 2019 Jon’s AD3 720, what interior colors? I’m needing a new driver’s door card in blue, hopefully with the bigger armrests/door pulls. Mostly only minor pieces I can’t find on the parts truck nearby. Found my door and various interior pieces. Need the trim piece just below the rear window, need the rectangular insert on the dash immediately next to the driver’s door, rear view mirror in decent shape 1 Quote Link to comment
PNW 720 97499 Posted February 17, 2019 Author Report Share Posted February 17, 2019 This weekend I’ll finally be getting around to getting a ground ran to see if that is my issue. I’m just curious if my dash lights and warning lights etc work, would that still be a ground issue? 1 Quote Link to comment
Jon's AD3 720 Posted February 17, 2019 Report Share Posted February 17, 2019 all three have brown interiors. two of them are rough. 1 Quote Link to comment
datzenmike Posted February 17, 2019 Report Share Posted February 17, 2019 15 hours ago, PNW 720 97499 said: This weekend I’ll finally be getting around to getting a ground ran to see if that is my issue. I’m just curious if my dash lights and warning lights etc work, would that still be a ground issue? Well everything electrical had to have some connection to the negative side of the battery to work. The dash harness is grounded to the body under the dash. From there it has to get to the block where the negative battery cable is bolted to it. 1 Quote Link to comment
PNW 720 97499 Posted February 18, 2019 Author Report Share Posted February 18, 2019 Problem was in the gauge assembly electrics itself. I went to pickup a long bed cap for my truck, and the fellow happened to have a dash laying out in the elements which he gave me. Plugged it in to see if the gauges would work, and lo and behold I had gauges. Swapped over speedo/odometer and the gauge backgrounds (elements weren't kind to the new-to-me assembly) and translucent bits. I'm pretty stoked about this. Now I just need to learn to re-cover my door cards and some seats which have rails, and this truck will be pretty well set 1 Quote Link to comment
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