Datsun Roadster Forum-311s.org

Trying to get my 70 SRL to pass NYS inspection. I had reverse lights when I left for the inspection shop but didn't have them when I got there...

Here's what I know, have the 12v at the red/blk wire connection near the clutch master cylinder. Have 12v at the reverse switch on the transmission, reverse switch works (switches closed in reverse). Have a solid ground at the lamp. No voltage at the red/blk wire at the lamp. Bulbs both check out as good. Is there a bullet connector connection between the reverse switch and the lamps? If so, where is it located?

From the schematic I see this:

I'm not sure Joe. I guess you might need to trace the harness back and see where it goes. Otherwise, just "temporarily" run a wire from the known good part of the circuit to the lamps. Good luck! Wish I was just a little bit closer...I would swing down and help.

There is a connector at the switch.

Not sure about the ‘70 but on the ‘68/‘69 there is a twin-lead red-black reverse switch cable with bullets on the switch end and bullet connections to a bundle of exposed bullet connectors in the harness below the brake master cylinder. That’s the scene of numerous possible poor connections, including fuel and temperature gauge harness connectors.

Thanks all, Yep the connection under the clutch master is good/clean, and the bullet connectors at the reverse switch is good. I actually jumped out the reverse switch and no voltage to the lamps. i have Voltage at the switch connection but not back to the lamps. i traced the harness along the left side frame and it is all taped up nice as from the factory. Must be a break in the wire somewhere between the switch and the lamps or a bad crimp on the bullet connector. I don't see any place for another bullet connection going back to the lamps.

Will try to find some time tomorrow to get back at it. I don't think there is any other connection between the switch and the lamps...may have to run a new wire as Matt suggests.

Update: another few hours up and down and underneath...let me start by saying all other lights work including the flashers. Put her in reverse, turn ignition on...turn signals working. 12 volts from the ignition switch gets to the reverse switch and then back up to the double bullet connector under the clutch master. Both connections have 12 volts (car in reverse). Poked around under the dash to find the red with blk wire. Probed thru the insultation with my test light. 12volts there. 0 Volts at the reverse lamps. Wire must be bad somewhere in the hardness. Need to pull the rear wheel as maybe it got free from the frame and rubbed. Thet's the best I got... The beer tasted good after all that fun.

I might have missed the answer in the translation, but did you test the reverse switch itself (removed from the transmission) for on and off functioning, by pushing it's button in and out ?
Mike

More diagnostic info in this thread :
viewtopic.php?t=3728=reverse+switch&start=15
Mike

Thank Mike, appreciate the input. yep, switch is good. There is the short 2-wire hardness that goes from the main harness under the clutch master to the reverse switch. Both wires are red/blk. It sends the ignition 12v to the reverse switch and when in reverse, the switch passes it back up to the main harness. All of the works. I also ohmed out the switch and it works. Shidfting in and out of reverse. Transmission was rebuilt about 10 years ago with a new switch. I ohmed out the reb/blk wire in harness from the connection under the clutch master to the reverse lamp and it is an open circuit.

Electrical problems are the worst. So much troubleshooting and investigation in areas that are difficult or uncomfortable to get to .... under the dash seems to be the worst!

Best of luck with the repair - seems like it's going to require running a new wire or tearing into the taped up harness to track down the short.

This will help you with the wires from the firewall to back.
https://kendo-usa.org/datsun/datsun_par ... _69_70.pdf

Power comes out of the dash harness to bullet connectors. Goes to switch then comes back up to the bullet connectors. It then runs a short distance back in the dash harness to the rear harness plugs, 2 and 3 pin and on to the back.

Connections for the lights are under the bumper. Harness runs along the back of the frame.

Check that you have power to the rear harness plug at the firewall. If so then examine the harness as it runs along the side of the frame. Sometimes they get damaged.

Curtis, you are da man. Found the 2 wire connector under under the brake master. Had to untape the engine harness at the firewall to be able to see it. Red/blk wire broke at the crimp terminal. Replaced and big joy!

I learned two things today. Where the connector back to the lamps is and to drink the beer before (and after) working on the roadsters!

Thanks everyone for your assistance!

You're welcome. Guess I should add some to that drawing.

Edit: I revised the drawing to show the reverse connections.

Curtis, the revised drawing is perfect!

jrusso07 wrote: Fri Jun 07, 2024 2:20 pm Curtis, the revised drawing is perfect!

Good, a bit more on there couldn't hurt.