View Full Version : TR6 TR6 electrical help

04-12-2012, 08:04 PM
I noticed the other day that the indicators on my '75 TR6 weren't working. Trying to trace the problem this evening as I promised my daughter I would drive her to school in the morning. I now find that the brake lights aren't working either. I figured this meant a blown fuse - I have Dan master's book and the Advance Wire schematic and see that the green fuse feeds both brake lights and indicators, but the fuse is fine (no sign of damage and I tried a good spare), and on further investigation found that the reverse lights work fine, so the fuse and power to the fuse must be okay. I know that the indicator bulbs are okay, as the hazard switch brings them all on, though at about double the normal frequency. I have yet to test the brake switch at the pedal, but that won't cure the indicators as well. It could be two separate problems, but I am hoping that someone out there will have some ideas on how to sort this out! Main points:

* indicators don't work - left or right
* brake lights don't work
* hazard lights flash at double speed
* reverse lights work
* tail lights work (which I think rules out bad ground at the brake light bulb?)

Thanks in advance for any help

04-12-2012, 08:10 PM
Check this out;

04-12-2012, 09:21 PM
Okay, children now in bed, so I can am back to the TR6. The brake switch didn't give any change in resistance when I pressed the pedal, so I stole one from the Stag (which won't need its brake lights for a few years at least), and now the brake lights work. The original Lucas switch (from the '70s) seems a lot nicer than the aftermarket one I had on the TR6, but what can you do?

Still struggling with the indicators though. I can't even find the flasher unit. The manual says on the driver's side (left hand drive) on the bulkhead near the feet, but I can't see it. Can anyone give me a hint where it is?

Thanks again

04-12-2012, 09:30 PM
On the passenger side top right side of the footwell. That's the turn indicator flasher. The hazard flasher is near the fuse box

04-12-2012, 10:10 PM
Ah-ha! There it is. No indication of a problem though. After fixing the brake lights by testing the switch, I decided to test the indicator switch. The wiring diabram shows three connecitons - light green and brown, which seems to be the common input, then green and red for left signal, green and white for right. I measured the resistance between the input and each output, and was a bit surprised to find that the resistance dropped to 0 for both directions - so LG/N to GR resistance dropped to 0 for the switch moving both left and right. Same for LG/N to GW. Does this indicate the switch is bad, or maybe a short at the hazard switch or turn signal indicator in the speedo? I didn't disconnect the wires, so as I think about it now I suspect that the "short" through the dash bulb would drop the resistance at both sides - but if that is the case then how does a single side flash? I am getting confused...

04-12-2012, 10:14 PM

The turn signal switch gets power from the hazard switch via that turn signal flasher. If the hazard switch does not fully connect after turning the hazards off, the wire to the turn signal circuit might not get 12v. I had to take the hazard switch out, clean & bend the contacts to get reliable power to the turn signals.


04-12-2012, 11:44 PM
Trying to take resistance readings with everything still connected will get you seriously confused! The problem is that bulb filaments have a very low resistance when the bulb is not lit. So with the switch closed either way, you were finding continuity either through the switch, or through the other side and through the bulb filaments.

As Jeff said, the hazard switch is a common problem spot when both turn signals don't work.

04-13-2012, 05:45 AM
I second Jeffs reply, I have a 71 and the hazard switch is different but I believe its function is the same, switch to hazard and it cuts out the turn signals switch it back and it cuts out the hazard circuit but if it doesnt switch back all the way neither work, I had that problem, I would switch to hazard and they would work and back to turn signals and nothing, I had to keep flipping the switch a few times and then the signals would work, I finally decided to replace the hazard switch at 200 buck mind you,,,and it works fine, Read the section in DM book on Hazard circuit it tells you why its set up that way. I would concentrate on the hazard switch, flip it back and forth a bunch of times and see if you can get it to work, could be cruded up contacts, if still no go see if you can take the switch apart, and clean it up. and since you switched to hazards and they work then bulbs are good and its getting power.


04-13-2012, 05:46 AM
Sounds like a bad ground connection. Not easy to locate,I had a similar problem with mt 73 TR6

04-13-2012, 09:53 AM
I finally decided to replace the hazard switch at 200 buck mind you,,,

FWIW, it should work fine if you bypass that function of the hazard switch. You just need to remember to turn off the turn switch if you are going to use the hazard switch.

When I was a kid, the family chariot was wired that way by the factory (it makes the hazard switch much simpler). I remember because, if you set all the switches just right, you could get the radio to play without the key. Back then, it wasn't child abuse to leave your kid in the car :smile:

04-13-2012, 08:10 PM
I disagree about the ground, if it was a bad ground the hazards would not work either, concentrate on the switch

by the way easier to eliminate the switch than a ground


04-14-2012, 10:21 AM
Thanks for all the advice. I think I will try to change out the hazard switch - I bought one a few years ago before I realised I could just buy the red part, and then forgot I had it! I hope that will fix the problem.