barricade88 Posted December 2, 2013 Report Share Posted December 2, 2013 I have a 78 Datsun 620. When I pull my light switch once, I don't have running lights or instrument lights or tail lights. When I pull it again I have headlights but nothing else. And now my temp gauge and gas gauge isn't working... And my charge light is on. What the hell is going on? Quote Link to comment
ggzilla Posted December 2, 2013 Report Share Posted December 2, 2013 Sounds like the dash isn't properly grounded. Or maybe the body ground is partially bad. Quote Link to comment
barricade88 Posted December 2, 2013 Author Report Share Posted December 2, 2013 How do I ground the dash? I thought my light switch wa bad so I tried to replace it but it is melted together... Quote Link to comment
tr8er Posted December 2, 2013 Report Share Posted December 2, 2013 Check the chassis ground. I can't imagine the dash losing ground. Battery negative cable to the steel body path could be corrupted/corroded. Quote Link to comment
Eagle_Adam Posted December 2, 2013 Report Share Posted December 2, 2013 if its melted together that would be a sign..... 2 Quote Link to comment
datzenmike Posted December 2, 2013 Report Share Posted December 2, 2013 I have a 78 Datsun 620. When I pull my light switch once, I don't have running lights or instrument lights or tail lights. When I pull it again I have headlights but nothing else. And now my temp gauge and gas gauge isn't working... And my charge light is on. What the hell is going on? . Probably would not hurt to clean the battery terminals and cable ends including the ground cable where it is bolted to the head behind the fuel pump. Somewhere on the Negative battery cable, probably near the negative terminal, there should be a second small wire going over to, and grounded to the body. It may be disconnected or broken. The other end of the negative battery cable is grounded to the engine block so you could just make a wire up (10 or 12 gauge to handle the current) and find a handy bolt on the block or head and connect to a good solid ground on the body. Make sure you have good lugs crimped on the ends and scrape off any paint. This has to be metal to metal and the wire has to be long enough to flex with engine movement. The gas and temp gauges are grounded differently. The gas gauge is through the body ground and then to the negative terminal. The temp gauge grounds to the block, to the negative cable and then to the neg terminal. Can't see how both are not working unless the volt regulator in the dash is bad or the upper left hand or fuse to the driver's left is blown. Assuming the body ground is fine then all marker, side, tail, license, dash and dash knob illumination is from the 10 amp fuse in the upper right hand side of the fuse box (closest to the driver) Quote Link to comment
ggzilla Posted December 2, 2013 Report Share Posted December 2, 2013 The dash is grounded by one screw.; if that was not tight then slight corrosion can happen over time. But a melted switch is a definite problem. Maybe the entire problem. Quote Link to comment
barricade88 Posted December 2, 2013 Author Report Share Posted December 2, 2013 Thank you!!! Where is the dash ground located?? And in going to check everything aroun the battery. Because I just replaced and sprayed my battery terminals. Quote Link to comment
tr8er Posted December 2, 2013 Report Share Posted December 2, 2013 You didn't by chance wire your battery backwards did you? Quote Link to comment
barricade88 Posted December 2, 2013 Author Report Share Posted December 2, 2013 Ha, no I didn't. Quote Link to comment
barricade88 Posted December 2, 2013 Author Report Share Posted December 2, 2013 I also have 3 double ought (however u spell it) grounds. 1 to the block, one to the frame, and one by the radiator.. Quote Link to comment
datzenmike Posted December 2, 2013 Report Share Posted December 2, 2013 The dash lights are not grounded through anything in the dash cluster. Instead, they are grounded through the dimmer switch which has it's own connection to the main harness ground going out to the engine bay. The temp gauge is grounded to the block. The gas gauge to the main chassis harness. The oil pressure is grounded at the block The E brake light is grounded at the hand brake The charge light is a ground return one way to the alternator. The only thing actually grounded at the dash cluster are the two turn signal lamps. Thank you!!! Where is the dash ground located?? And in going to check everything aroun the battery. Because I just replaced and sprayed my battery terminals. . When replacing the negative cable, did you see a ground wire to the body sheet metal? Quote Link to comment
BenJammin Posted December 3, 2013 Report Share Posted December 3, 2013 The dash lights are not grounded through anything in the dash cluster. Instead, they are grounded through the dimmer switch which has it's own connection to the main harness ground going out to the engine bay. The temp gauge is grounded to the block. The gas gauge to the main chassis harness. The oil pressure is grounded at the block The E brake light is grounded at the hand brake The charge light is a ground return one way to the alternator. The only thing actually grounded at the dash cluster are the two turn signal lamps. . When replacing the negative cable, did you see a ground wire to the body sheet metal? ... great info as always from the KingRat ! When I wired up a factory tach, it had what seemed like a natural/intuitive ground connector on the cluster also ? Quote Link to comment
datzenmike Posted December 3, 2013 Report Share Posted December 3, 2013 Well, prior to '76? there was no tach option (though there was a clock) so you would have to make your own ground connection to the main harness or to any handy sheet metal screw if retrofitting one. On the 620s that did have a tach option, the ground isn't in or even to the dash cluster, but is contained in the tach wiring plug on the main harness. You could remove the tach from the dash and it would still work if plugged in.... even the dim-able lights. Quote Link to comment
BenJammin Posted December 3, 2013 Report Share Posted December 3, 2013 Maybe it was just the lug for a clock then... didn't seem to be serving any purpose otherwise and was convenient to ground the tach there (it just had bare wires... no harness plug). But as for OP... I would just test the switch and other cluster components according to the fsm.... but sounds like the light switch is fried anyway (?) Quote Link to comment
datzenmike Posted December 3, 2013 Report Share Posted December 3, 2013 Could be a ground problem as there are several things not working. OR there are more than one problem. The parking lights are on a separate fuse (closest to driver on right side of box) It's 10 amp but may be loose or no good. Briefly hold a quarter across the fuse clips. If the lights come on then the fuse is bad. If the oil pressure light comes on when the key is turned to ON then there is power to the fuel/temp gauges, brake, and charge lights. If there is no oil pressure lamp then replace the fuse closest the driver on the left side. Quote Link to comment
Eagle_Adam Posted December 3, 2013 Report Share Posted December 3, 2013 Briefly hold a quarter across the fuse clips. If the lights come on then the fuse is bad. Good easy test! Quote Link to comment
barricade88 Posted December 3, 2013 Author Report Share Posted December 3, 2013 Thanks eagle Adam and datzenmike!! I'm going to try all that. I think my light switch itself is bad and so is the connectors but they melted together... So idk how I'm going to get it off. ALSO!! Under the dash by the dimmer switch there is a silder thing that looks like it connects to something but nothing is hooked to it. Idk what it's for tho? Quote Link to comment
Eagle_Adam Posted December 3, 2013 Report Share Posted December 3, 2013 pics man, we need pics to help you Quote Link to comment
barricade88 Posted December 3, 2013 Author Report Share Posted December 3, 2013 I know, I'm on my phone and I don't know how to upload pictures Quote Link to comment
Eagle_Adam Posted December 3, 2013 Report Share Posted December 3, 2013 download the photobucket app upload pics to the app paste the IMG link on ratsun DONE now..... make with the pics 1 Quote Link to comment
barricade88 Posted December 3, 2013 Author Report Share Posted December 3, 2013 Okay hang on! 1 Quote Link to comment
barricade88 Posted December 3, 2013 Author Report Share Posted December 3, 2013 1 Quote Link to comment
barricade88 Posted December 3, 2013 Author Report Share Posted December 3, 2013 And this is the light switch... Quote Link to comment
Eagle_Adam Posted December 3, 2013 Report Share Posted December 3, 2013 nothing looks melted to me..... Quote Link to comment
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