71 Datsun 240z Signal Problems "Please Help"

[tayS30lor]

Hello all,

 

Car 1971 Datsun 240z HLS30-22328

 

I am having rear turn signal problems.

 

I had a hacked up front engine wire harness in the car. I changed it out to a new cleaner un molested harness. I have cleaned all connectors in the car with contact cleaner and a tooth brush and so on.

 

The problem I am having is, when I turn on the signals to go left... Just the front LH signal comes on and not the rear. When I put the signals on to go right. The RH front signal works and both the LH and RH rear come on. I have tried switching out the signal switch and I have the same problem. I have by-passed the flasher unit and again I get the same response. I have tried as well 2 different rear wire harnesses in the car and yet again the same problem. Not even a slight response out of the LH rear signal at all!!!

 

I have also put new bulbs in and gone over the dash wire harness and it does not look like its had any work or been modifyed in any way.

 

If anyone has any ideas. I would love the help.

 

Thanks,

Edited October 16, 2011 by tayS30lor

[clutchdust]

Sounds like you've covered most of the things I would suggest. I am curious about the turn signal switch you switched out. Mine was a problem and took quite a bit of fiddling to get working. I'm betting that's the source. The other thing I would suggest, regardless of how everything else works, is splice in additional grounds directly at the rear where the light plugs in the housings.

[Dershum]

I know that in my 71 when I was digging thru the wiring there was a straight-shot line from the front-left turn signal all the way back to the tail lights. I'm not sure this is "stock" but it was run straight through the cabin and I had to re-route it because my foot kept catching on it. My point is you might just want to make sure there's not a crimp or break in that line. Also, on mine, there were three wires in the bundle, but only the positive was connected. I did a voltage test on the other two but they were either grounds or not connected to anything up front. I capped them off and moved on. My point is this, I _think_ you only need one positive line from the turn signals up front to the rear, and the turn signals in the rear are in serial so you should be able to trace it relatively easily.

 

Just my 2 cents.

[clutchdust]

For one thing we need to understand exactly what happens with the turn/brake lights, especially the rear lights. The front turn lights are pretty much a straight shot off the signal switch (technically, so are the rear) but the difference is within the switch itself is an interrupter that opens the brake light circuit when the turn signal is turned on. So that what happens is when you press the brake pedal, both tail lights illuminate. However, when you select a turn signal, the interrupter breaks connection with the brake light on that side and switches that circuit through the flasher. This becomes a problem with age as all manner of things happen to the turn signal switch.

Now it's been a while since I last had my switch apart so I can't remember exactly which wires are the culprit but I do seem to recall green with white or yellow tracers being involved.

Anyway, back to the issue, if the interrupter doesn't break the connection with the brake light, when you turn on the signal it really screws things up. In mine, it was causing a short that actually melted the solder and the turn signal wire would come off the switch. I resoldered it a half dozen times before I finally figured out what was going on.

So when you pull your switch apart you will see four contacts in an 'H' configuration on a central rocker point. These are the actual contacts for the turn signals. One side of the 'H' controls the left, the other the right. The reason there is an 'H' instead of a single contact for each side is because of the interrupter circuit. Now if you look off to the side of the 'H' you will see a pair of normally closed contacts (for the brake lights) mounted perpendicular. These should be closed when the switch is in the neutral position, but should open one side when a turn signal is selected. If it doesn't it wonks up the works and will often cause problems like the OP is describing. I am not sure of the method of failure, I suppose it's just age and heat. In my case, I just re-bent the contact so it remained in contact until the turn signal was switched. Ever since my signals have worked pretty much flawlessly.

If it doesn't help the OP, I hope it helps some others.