TR7 Headlamps

[Nige T]

I'm getting around to the next fix on my TR7, the headlamps. When the light switch is turned on, the side / headlights come on, however the lights don't rise. Until recently, the lights would pop up and down when pulling the flasher stalk. Now, the offside light has stuck in the up position and the nearside light only will operate from the flasher stalk, albeit sporadically. I do hear the clicking from the glove box area every time I pull the flasher! So far, I have fitted a new light switch, cleaned all connections with electrical spray, checked the relays which all seem okay and greased the headlamp mechanisms. I can't for the life of me find the Pektron unit! I have tried to wind down the offside headlamp using the motor knob, but no go. Any suggestions on where else to look would be appreciated.

[Howard]

Nige

Detailed explanation of how the Headlamp systems works shown on the attached drawings / last sheet. The Pektron will be found on the lower right of the 12 way fueboard. Its not clamped in place so may be behind the relays.

Cheers

Howard

1981 TR7 DHC Wiring Diagram Rev 7 03_2023.pdf

[Nige T]

Thanks Howard. Electrics are not my strong point, but I'll give it a go! 

Cheers,

Nigel

[Howard]

Always the first area to check is the headlamp earth connections under the bonnet.

Next thing to check is do the lights come on, even if they don't pop up.

Please check both of these and then we can investigate from there.

[Nige T]

The earthing points are good and both side and headlights work although the lights don't pop up!

Cheers,

Nigel

[Howard]

OK lets try the next check. If you have a multimeter this good, but a bulb holder & 10/15w bulb (with a fuse in line to protect any short circuits!) is even better.

Unplug the connectors just behind the headlamp pods that have the blue / purple & blue / brown wires that feed to the headlamp motors.

Connect one side of the bulb / multimeter to a suitable earth.

With everything switched off, connect the multimeter / bulb wire to the blue/brown wire. You should then see +12v or the test bulb should light.

Next connect the multimeter / bulb wire to the blue/purple wire & move the dashboard switch to the headlight on position. You should then see +12v or the test bulb should light when touching the the blue/purple wire.

This will confirm if the problem is with the headlamp motors or the circuits feeding them. The Pektron unit is not being checked at this stage, but we can check it later on.

 

 

[Nige T]

Many thanks Howard, will report on progress!

[Nige T]

Hi Howard, 

I have followed your instructions and got 12 volt readings on both wires, both sides. I am guessing I will now need to look at the motors?

Cheers,

Nigel

[Howard]

Nigel, not yet - there are more relays involved. We are on the NC 500 right now and so will get back to you tomorrow.

Cheers

Howard

[Nige T]

Thanks Howard, no rush!

[Howard]

Sorry for delay, but will try to post tests to check motor operation in next couple of days - as you will have seen my car failed in Inverness so have been sorting it out.

Cheers

Howard

[Howard]

See attached photo for motor testing procedure.

[Nige T]

Hi Howard,

Thanks for sending the testing procedure.

I have had bit of a problem logging in, hopefully this will get through.

When following the procedure, I got the following results :-

With the headlamp switch turned on, when reconnecting the battery the headlamps stayed in the slightly raised position, i.e. nothing happened!

When the headlamps were switched to the off position, the nearside headlamp returned to the fully down position, however the offside headlamp went to the fully raised position and stayed there!

Seems like I've opened a right can of worms here 🙂

Cheers,

Nigel

 

 

[Howard]

Nigel,

That's a good start. It proves the motors are working and that the problem is with the contacts on the lights or the associated relays.

Can you repeat the test, but this time wind the lights to the fully up position before reconnecting the supply.

[Matt306]

I think the old relays in the fuse box can be replaced with modern equivalents?

[Howard]

The relays are DRC1820 which are standard and still readily available.

[Nige T]

Hi Howard,

Got around to testing last night. With the pods wound up to full height, when reconnecting the battery with the headlamp switch turned on, there was no movement. When the switch was turned off, the nearside pod dropped down to the fully closed position, however the offside pod remained in the fully raised position. It may be worth mentioning that the flasher stalk does feel quite loose and sloppy and prior to dousing it with contact spray, both pods raised and lowered when using the stalk. Not long after spraying, only the nearside pod would work off the stalk.

Cheers,

Nigel