My headlight’s winking at me!

[Saltire]

The Elan’s developed a rather odd habit in the past few weeks. I start the car in the garage, headlamps down, and drive off to wherever I’m going (headlamps still down). A few seconds after I stop and turn the ignition off, the left hand headlamp pod. will pop up. Sometimes it comes all the way, sometimes only half way. The lights do not come on. If I cycle the light switch (on/off) both pods go down and stay down. It doesn’t happen every time, but most times.

The motors were overhauled a year or so ago and otherwise operate normally.

I’ve had the pod lift module out of the car and apart, and I can’t see any evidence of solder failure or other problems inside the unit.

I’ve checked all the connections for tightness, cleanliness, good earths, etc.

While I find the behaviour quite endearing, on balance I’d prefer it wasn’t happening.

Has anyone else experienced this? And given that the only other thing I can think of is a failure deep within the pod lift module, does anyone have a spare one I could borrow to substitute temporarily, before I spend north of £100 with SJs on a new one.

Ideas welcome, and thanks

[Tuga2112]

the only thing you havent mentioned that i would do, was to follow the wires from the motor all the way back to the module. check if theres any place where they have exposed copper that may ground on contact when the car stops shaking.
(now that im thinking about it, you need to test if either or both of the wires are live when the motors are not moving. if the resting voltage of the circuit is 0v even a short wouldnt make the motors move.)

when inspecting for solder cracks, I have found in the past that even with a 10x magnifying glass cracks are sometimes not visible. (this was experienced with a surround sound remote controller) reflowing all the joints is tedious, but efficient.

[Saltire]

the only thing you havent mentioned that i would do, was to follow the wires from the motor all the way back to the module. check if theres any place where they have exposed copper that may ground on contact when the car stops shaking.
(now that im thinking about it, you need to test if either or both of the wires are live when the motors are not moving. if the resting voltage of the circuit is 0v even a short wouldnt make the motors move.)

when inspecting for solder cracks, I have found in the past that even with a 10x magnifying glass cracks are sometimes not visible. (this was experienced with a surround sound remote controller) reflowing all the joints is tedious, but efficient.

Thanks, Joao, good thoughts which I’ll follow up over the weekend

[peteoddcar]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.
Test the ground circuit resistance and the terminal pressure
I think it grounds at the pedal box. Something slightly loose there maybe?

[Tuga2112]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.

I know from my expeirence with that module a few years ago that the mosfets used internally to close the ground circuit to the motors are of a type that is extremely outdated today, they also had rather poor heat dissipation capacity compared to modern mosfets of the same ratings.
(the one that failed me, clearly had burn marks in the area)
the faulty one was replaced by a different model, a lot more modern which had heat dissipation improved by a large magnitude (it was more than 10x better from recollection) My replacement was installed without a heatsink which was a controversial decision back then.

Jonathan, if you would like to replace the mosfet, I can send you a couple on the mail. I should have about 20 of the same model i used in mine which were used for my windows close on lock circuitry, you would pay more for P&P than their value from any retailer. specially at the small amounts required.

[Saltire]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.
Test the ground circuit resistance and the terminal pressure
I think it grounds at the pedal box. Something slightly loose there maybe?

Thanks, Pete, that’s a really interesting suggestion. And I wouldn’t dream of shooting you for the “back EMF” comment - but then I understand what it means

I’ll check the resistance and the grounding again, although if it’s an earth issue it puzzles me why both pods wouldn’t show the same behaviour.

Thanks again

[Saltire]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.

Jonathan, if you would like to replace the mosfet, I can send you a couple on the mail. I should have about 20 of the same model i used in mine which were used for my windows close on lock circuitry, you would pay more for P&P than their value from any retailer. specially at the small amounts required.

Thanks, Joao, that’s a very kind offer, and I’ll happily refund postage. You have PM.

[GeoffSmith]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.
Test the ground circuit resistance and the terminal pressure
I think it grounds at the pedal box. Something slightly loose there maybe?

Can't remember who had this problem many years ago and it was a problem with noise generated by a poor erf {note correct spelling Pete } causing one side of the module to trip but not the other.

[peteoddcar]

Poor Erfs - gremlin food. A nice drop of verdigris goes down well with them too.I’d suggest a 90 or 91 from the northern hemisphere.

[Saltire]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.
Test the ground circuit resistance and the terminal pressure
I think it grounds at the pedal box. Something slightly loose there maybe?

Can't remember who had this problem many years ago and it was a problem with noise generated by a poor erf {note correct spelling Pete } causing one side of the module to trip but not the other.

And there was me thinking erf was a truck manufacturer

I suppose, Geoff, you don’t recall what the cure was in the earlier case?

[GeoffSmith]

Sounds to me like the module has become sensitive to spikes for some reason ( that I call back emf - don’t shoot me Electronics boffins ) generated by key off.
Test the ground circuit resistance and the terminal pressure
I think it grounds at the pedal box. Something slightly loose there maybe?

Can't remember who had this problem many years ago and it was a problem with noise generated by a poor erf {note correct spelling Pete } causing one side of the module to trip but not the other.

And there was me thinking erf was a truck manufacturer

I suppose, Geoff, you don’t recall what the cure was in the earlier case?

I can't be 100% sure but I've got a feeling it was a bad earth connection on the manifold. I would recommend cleaning the earthing points preferably with a spray of Electrolube EML.

[Saltire]

Thanks, Geoff much appreciated

[Saltire]

5DCD9E35-3919-49F8-9C09-0A0B2B34241F.jpeg

Well, cleaning the earths didn't fix it

Joao has kindly sent me two MOSFETS for the motor control module, so that’s the next step. Otherwise it looks like a completely new module at upwards of £100 from SJs.

[Tuga2112]

any progress john ?

[Saltire]

Thanks for asking Joao.

I’m due an MoT next Wednesday, so I’m deliberately not tempting fate by opening up the headlamp control module at this stage. Once I’ve - touch wood - passed the MoT, I’ll get back to the investigation.

Interestingly, as I was putting the car back in the garage today, I switched off the engine, and the pod popped up as usual. Then I realised I hadn’t reversed into the garage quite far enough, so I restarted the engine - and both pods came up and stayed up. Once I’d reversed a few inches and switched off again, they both went down and stayed down of their own accord. At no point did I touch the light switch or flasher lever.

And I never get the abnormal behaviour when I use the headlamp flasher

I’ll keep you posted

[JethroGreenfinger]

Hello Saltire, did you ever find a solution for this? My N/S light pod pops up about 5 seconds after the lights have been turned off and stays up! The lights are not on and the O/S pod is down. The motor gets really warm, but the knob is not turning and it is not jammed in any way. Both headlight pod motors were refurbished only a few weeks ago.

[Saltire]

Hello Saltire, did you ever find a solution for this? My N/S light pod pops up about 5 seconds after the lights have been turned off and stays up! The lights are not on and the O/S pod is down. The motor gets really warm, but the knob is not turning and it is not jammed in any way. Both headlight pod motors were refurbished only a few weeks ago.

There’s an update in another thread somewhere. I managed to dismantle and repair the old headlamp control module with the two MOSFETS which Jōao kindly provided, but I also got hold of a new module. Both work in the car; no more flaky headlamps.

I suspect that the old electronics in the control modules are starting to break down 30+ years on, so I anticipate we’ll be seeing more reports of this behaviour.

[JethroGreenfinger]

Thanks, that is useful to know. I have re-flowed my controller, but yes maybe the parts are just getting old. Thanks