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TR5/TR250 Question on Lucas Hazard relay

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T

TuffTR250

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My TR250 has an original Lucas 6RA hazard relay for the hazard lights and turn signals. When I turn on the battery shut-off switch, the relay makes a clunking noise and vibrates. My turn signals are not working. The relay has never made a sound before when I turned on the battery shut-off switch. Am I correct to believe that the relay has failed? If it has failed, is there any way to take it apart and repair it? Thanks!
Bob
 
Where is your battery cutoff switch in the circuit? With the battery isolated from the car's electrics nothing should be powered at all. Can you post a link to a -250 wiring diagram?
 
Bob, I hadn't realized you were in Raleigh. What part of town?

OK, you said the cutoff switch is on the negative pole of the battery and the wiring diagram says your car should be negative ground. Therefore, when you disconnect or turn off the switch, there should be no current flowing to anything on the car. Nothing should be powered.

Do you have any other things connected directly to the battery negative terminal? Is your cutoff switch one of the FIA type racing switches with additional contacts on it other than the battery cables?

EDIT: I was also slack on not checking this earlier. You said your car has the Lucas 6RA for the turn signals and flashers. 6RA shows up as a multipurpose relay, not a flasher unit. Can you be more specific about what is going on and what is buzzing?
 
I'm in north Raleigh near Lynn Road school. I have the shut-off switch with the green knob that is screwed/unscrewed to connect/unconnect. Nothing else is on the negative pole of the battery. I noticed that a lot of descriptions of the 6RA relay is something other than hazard relay, however I am pretty sure that it is the original hazard relay on the car. I've had the car since 1982 and this is the first failure of that relay. Of course it is possible that a PO replaced the relay at some point before 1982.

What is happening is that when I turn on the battery shut-off switch the old hazard relay makes a loud clunk noise. I have front and rear marker lights and rear tail lights, but no turn signal lights in back nor in front. I have LED "bulbs" in both front and back turn signals. I bench tested all LED bulbs and they are all good. I have bench tested the turn signal flasher. I have a new solid state hazard relay from Moss (171-320), and still no turn signals. I have not yet tested the turn signal switch nor the hazard switch since they are in the mass of wires under the dash. I'm thinking since the new solid state hazard relay did not help, my old 6RA relay may still be ok. I'll have to keep trouble shooting to see where the problem is.
Bob
 
I'll study this a bit more tonight regarding the presence of the relay. The -250 wiring is a bit different than I am used to in that area.

Does the picture below represent what your disconnect looks like? If so, removing the green knob AND separating the two halves of the "switch" removes all power from the whole car so nothing should "buzz". If you don't physically pull the halves apart some current will still pass through to the car.


https://www.jegs.com/images/photos/700/710/710-74103.jpg
710-74103.jpg
 

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Bob, you may have more than one issue. First, I think you should know that flasher units that work fine with regular incandescent bulbs may not function at all with LED bulbs. Even the flashers marked "Electronic" or "Heavy Duty" relies on a certain amount of current flowing through the device for it to function. Special LED flasher units are available, but most have different physical pin-out spacing from the standard flasher units. You could add LOAD RESISTERS to allow the unit to flash, but that seems like a silly idea to me (but it can make the flasher work). LED lights take much less power (current flow) so you may have to deal with that.

You also should know that the HAZARDs and TURN SIGNALS are really two separate circuits sharing the same bulbs. The TURN SIGNALS are powered by the GREEN wire (switched hot with the ignition key) while the HAZARDs are powered by the PURPLE (always hot) wire. The hazard switch disables the function of the turn signals by breaking the circuit from the turn-signal flasher to the turn-signal switch, and at the same time energizes your generic relay to connect the left and right sides in series with the hazard flasher. (The PR or purple with red tracer wire is powered by connecting 1 and 2 of the hazard switch when the hazard switch is turned on -and disconnects 4 from 3.)

But, you say the relay clicks when you turn on the battery power (or screw down the post). That should not happen. Somehow, +12v is getting to the PR wire without the switch being turned on. My guess is your hazard switch is not wired properly, or is broken. You need to be careful with this diagnosis because you are working with some wires that are always powered. As a test, you may want to pull the fuse on the purple wire to see if the relay no longer clicks when you connect the battery. You may decide to solve one problem at a time -the HAZARDs or the TURN SIGNALs.

Good luck, I just went through this on a TR4A rewire, but the difference was in the way the new LED style flasher units need wired differently.
 
There is little to be added to Texas' post.

As he said, with the battery connected, the relay should not hum, buzz, or click. If you pull the fuse for the purple wire circuit and the relay calms down, that says power is getting through the hazard switch and moving on to the relay (damaged/broken switch).

Let us know what you find when you remove the fuse.
 
Thanks Texas and Doug! Your post has given me ideas about troubleshooting. I'm leaning toward believing the hazard switch may be bad. It is a miserable job to get the switch out of the dash, so first I'm working to test around it to isolate it. Just too much other non-Triumph stuff to do so my trouble shooting is going slowly.
Bob
 
Let us know what you find out.

Should you need any help, I am only a short distance away near Southpoint Mall in Durham.
 
Found the problem was the hazard switch. My son came over and we repeated my previous trouble shooting to isolate each piece in the circuit. That pointed to the hazard switch. So we made sure the connectors were all pushed well onto the hazard switch terminals. Then my son flipped the hazard switch off and on quite a few times and it started working. I guess that must have cleaned the contacts. And the original 6RA hazard relay is working fine. Thanks for the help on this problem!!
Bob
 
That's great. Thanks for posting what you found.

Out of curiousity, do you attend the MG Car Club show? If not, please consider it in the future. The show has been held annually for about 20 years with the venue being North Hills for the past decade or so. The show is open to all British cars, not just MGs. My wife takes her GT6 every year and I take my Mini. There is typically only one TR-250 there mixed with the TR-6s. It would be great to see another -250 at the show.
 
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