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TR7 headlight problems


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Hi together,

since a few years we have beside 2 GT6 (one convertible with TR6PI) also a TR7 Coupe. :)

 

1. Since the beginning we have the problem, that both headlight motors are only moving if you pull the flash light button. Once the lamps are up and you switch on the lights with the main switch both remained upright. Switching off the main headlight switch let the lamps go down.

Any idea where I can search for the failure??

 

2. Since a few days the left headlight goes up as the right one, but after a few miles and voibrations the headlight goes down. Switching off and switching on leads again to the upright position, but same effect headlight going down repeats.

After a break (temperature effect) suddently the headlight remains in the upright position as it should be.

 

Someone told me the lifting motor has a contact problem, I removed the motor and open it, but everything looks well.

My question is now how the headlight remains in the upright position? If I look on the wiring ciruit there is no power on there engine, otherwise the engine would run and the headlight goes up and down.

 

Any idea what I should do?? :angry:

 

Regards

 

Rudi from Germany

 

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Hi Rudi & welcome!

 

Now is the time to give your headlights a little service.

 

Start by cleaning up all the earthing/grounding points ( take out, clean and put back with a dose of Vaseline the main two are within the bonnet/hood area just behind the light units) black wires attached by a bolt to the body.

 

Then take apart and clean the two red and two clear wire connectors in the same area. If you are feeling brave takeout, strip down and clean the master light switch on the dashboard.

 

Take care with all of the plastic parts as they have a nasty habit of snapping.

 

If you have taken the headlight pods and motors off the car. Clean and re-grease the pivot points, this will make them run much smoother and you will be able to check that nothing is worn out.

 

Nothing too bad - let me know how you get on.

 

Cheers

 

Ian

Edited by TR8IAN
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Hi Ian,

 

thanks for your feedback.

 

Master light switch I have already changed.

I'll have alook on the grounding points the next days.

 

But can you tell me how the lights are kept in upright position?? It can't be electric with the motor, must be somehow mechanic...

I've seen a spring there, but everything looks correct with it.

 

If I understand the principle I can search for the failure...

 

Thanks for your help.

 

Regards

Rudi

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Hi Rudi,

 

The motor for each headlight pod runs in one direction only, the UP cycle is a rotation of 216 degrees & the DOWN cycle is the remaining 144 degrees of on full rotation. When the pod has reached the UP position the limit switch on the motor breaks the circuit & the motor is connected to earth through the run/stop relay (located in the fusebox area) which gives electrical breaking to stop the motor very quickly in the correct position. The pod is held in place by the link rod under the pod assembly. The spring is there just to balance the weight of the pod assembly.

 

When you turn the light switch off the motors are connected to power again, & rotate the other 144 degrees of the cycle until the limit switch again breaks the circuit, the motor is again earthed through the run/stop relay & stops in the correct down position.

 

Check the main/dip/flash stalk on the steering column & clean the contacts for the main/dip beam connections - this is part of the circuit. Find & clean the earths for the run/stop relays as well as the earths in the engine bay behind the headlights.

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Hi Anthony,

 

thanks for the explaination.

But if like in my case one headlight is going down 50-70% of the way very slowly in a few minutes that means that the motor is maybe not earthed by the run/stop relay.

Maybe I should firts changed both run/stop relays to see if the failure remains with the left light.

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Rudi,

 

Before you change the relays, most of the headlight problems we see are down to poor earth and continuity in the electrical system - try cleaning all the connectors and earths - this quite often does the trick before you have to spend hard cash.

 

Cheers

 

Ian

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Rudi, I agree with ian, go through and clean all the earths & connections including the main/dip beam connections on the stalk.

 

There is a run/stop relay for each headlight circuit, you could swap over the relays to opposite sides to see if the problem stays on the left or moves to the right. if the problem goes to the right then it is likely to be caused by a faulty relay, you can replace that relay. If the problem remains on the left side, then you know that you need to investigate the rest of the left side motor circuit.

 

The headlight system is really not that complicated but there are a number of reasons that could cause the problem so it is a matter of checking one thing at a time. That can be boring but let us know how you get on!

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My right headlight motor started to play up, and I was not looking forward to wrestling with wiring diagrams, relays and switches and stuff, but I welt out and bought a can of aerosol contact cleaner, and opened up the red connectors at the front, gave them a good spray and cleanup, and put them back together. Problem went away. No guarantees but it costs next to nothing in time and money, so worth a try.

 

Good luck

Al

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Hi

Check out the Pectron relay I had the same problem with the headlights the same as you,bring the lights up with the flasher switch and then switch the main switch on, i tried two s/h units with no success i managed to get another which we checked before fitting it and that was okay cured the problem when we opened one of the pectron units we found that the diode had blown, worth a try try anyway.

Cheers

Moe

Edited by moe and ess
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Hi Peter do you know what the ref number is for the diodes in the lift motor as they have both blown in my

offside headlamp, fortunately I have a spare pair and I am at present swapping the motors over but I would like to

repair the blown motor, trouble is I can't quite make out the rating on the diodes.

Cheers

Moe

Edited by moe and ess
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Hi guys,

 

Possibly the best way of dealing with the lift motors is to throw them away. In an effort to reduce weight and maintenance issues, I pulled the whole headlamp assembly out and re-thought it. I cut most of the metal out of the steel frame that supports the headlight cowling which reduced the weight significantly. I took the motors out and replaced each of them with a linear actuator (which only weigh 700g each). I fixed one end to the steel frame and the other to a simple little bracket fixed to the inside of the wheel well. It was fiddly because the actuators operate over a fixed range and if they are forced to stop before they get to the end of their range the motor will burn out. They change the direction of travel by reversing the polarity. I had my regular mechanics tech guy do the wiring and he said it was a major job, but I am suspicious that he just didn't know how to do it.

 

The linear actuators I used are designed for what they call "off-highway vehicles", meaning agricultural and mining machines. They should be very water, vibration, shock and heat resistant. The manufacturer is Linack and If you are interested I will look up the model I used.

 

I am not real good on electrics so would be interested to hear if anyone has any ideas on why it should have been so difficult to wire these in. Is it hard to install a reverse-polarity switch?

 

Cheers

 

Michael

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Hello to all,

 

yesterday we found time to work on the car.

I changed the lifting motor and checked renewed all relevant cables/connections.

At the end the headlaights came up/down as before, but still only will pushing the flash lights.

We found in the Pektron unit one diode broken. Changing that diode was leading to the final result: everything is working as it should :D

The headlights are now the first time since we have the car (4 years) going up by using the master light switch as it should...

 

Thank you all for your hints and comments, it was a great help for me fixing the problems.

 

Regards

 

Rudi

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For what it's worth, I always add a relay in the dash, just behind the main light switch

 

Easy, and effective.

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  • 7 years later...

This is a great old thread.  Got me thinking about this Pektron Relay.  My situation may be different, My right motor never goes up or down using the switch.  With the switch on and left light up (you can then hear the circuit breaker click), I can spin the know and half way through, the light goes up (circuit breaker stops clicking).  I turn the switch to off and the left goes down, right stays up.

I partly opened the motor, just enough to see the commutator, I spray deoxit directly on the commutator.  I don't want to go any further as I will have no idea on how to get the brushes back on.  I cleaned and regreased the gear mechanism that lifts/lowers the headlight. 

Same results.  To me, it seems as if the motor needs new brushes or do you think it's that pektron relay?

Thanks in advance,

Leo

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For a detailed explanation of how the Pektron works + detailed circuit diagram see my attached TR7 wiring diagrams. Sheet 2 shows the headlight motor details, Sheet 5 explains how the motor switches work and a subsequent addition on sheet 7 provides full details of the Pektron internal circuit with an explanation. Hope this helps with the fault finding

Howard

UK DHC 1980-81 TR7 (2020-09) with pektron fuel gauge & fan details.pdf

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