HEDALIGHT Disperate faulty, Unexpected fault Options

[searunner]

The DIODE APPEARS good. (I test the PASSENGER SIDE) My opinion is that is VERY strange that gremlins appear when the
BATTERY is OFF
-the LIGHT SWITCH is OFF
The ACCENSION KEY is OFF
and the HEADLIGHT (passenger side) is UP & DAWN continue
The CAR in this condition have to be ALL under KEY
And Passenger HEADLIGHT OFF. Now I must investigate the Key Relay

Can you elaborate what you mean by gremlins appear when the battery is off? I believe you said previously that if the battery is disconnected that this stops the up/down moment (as it should).

Is your car euro spec or an imported US car?

Yes is a My mistake BATTERY is ON (CONNECTED)
The others entry item are corrects.
Is in this configuration that the Passenger Headlight beginning to go UP & DAWN
as log as I am reentered in to the garage.
My car was build in the 73 and sell in Italy in the 74

[Superhawk996]

How about post #20

What happens removing the relays one at a time while the condition is occurring?

Happy to try to assist working through troubleshooting. Pulling the relays one at a time is a first step to understanding where the motor that is continually cycling is getting the power feed from.

Won’t be easy to go back and forth quickly due to time zones but will try to assist.

[emerygt350]

How about post #20

What happens removing the relays one at a time while the condition is occurring?

Happy to try to assist working through troubleshooting. Pulling the relays one at a time is a first step to understanding where the motor that is continually cycling is getting the power feed from.

Won’t be easy to go back and forth quickly due to time zones but will try to assist.

Somebody got a picture of the relays? I am not sure he understands what we are describing.

[Spoke]

@emerygt350
@Superhawk996

Here is the basic schematic for the headlight motors. This is from a Haynes manual. Not sure I understand how the switches in the motor are configured. Are they switches riding on a cam or slide contacts on a PCB wheel?

The headlight switch is shown in the PARKING position where both UP and DOWN contacts are open. The headlight position is 1/2 up/down and both switches are closed. Both motors are off.

If in the DOWN position, the headlight switch provides power to the DOWN switch which is closed and the motor cycles until the cam/PCB wheel opens the DOWN switch.

If in the UP position, the same thing happens except the motor stops in the UP position.

Notice the headlight switch is not fused according to Haynes. Yikes!

For the life of me I can't figure out what the diodes do. Assuming they minimize interaction between the 2 motors but I can't figure it out.

For the issue for @searunner where the motor stops at UP but cycles up/down on DOWN, the switch in the motor for DOWN is not opening up. If the relay was sticking on, it would stick on for UP too.

[Superhawk996]

For the life of me I can't figure out what the diodes do. Assuming they minimize interaction between the 2 motors but I can't figure it out.

Not sure what you mean. You have it correct.

Since the headlamp motors cannot be synchronized, the diodes block current flow between the UP & Down circuits during the period when the rotary switch would otherwise allow continuity between those circuits when they are between fully up or fully down.

The way the Haynes manual shows the rotary switch matches its physical layout.

Picture below ( @georgekopf ) photos

[Spoke]

For the life of me I can't figure out what the diodes do. Assuming they minimize interaction between the 2 motors but I can't figure it out.

Not sure what you mean. You have it correct.

Since the headlamp motors cannot be synchronized, the diodes block current flow between the UP & Down circuits during the period when the rotary switch would otherwise allow continuity between those circuits when they are between fully up or fully down.

OK I see what the diodes do. Question is would a dead or shorted diode cause the up/down observed?

Thanks for the pictures. I didn't think there were switches in there. Back to the original up/down issue, what are the chances that there's metallic build up on the insulator for the down wiper? What else could cause the down to skip right through the stop to cycle again?

[BeatNavy]

FWIW, I had strange headlight behavior for years. When I turned the lights on, the passenger side light would pop up normally but the driver side would "wink" -- it would go up, then down, then back up again. I thought it was kind of amusing, but eventually I decided to troubleshoot it.

The root cause was that one of the solder connections on the diode on the passenger side had a hairline break. From what I recall, those diodes are pretty small, and I didn't see the fault initially. Resoldered the connection and everything worked normally again.

Point being: the engineering on these lights is complicated, and in addition to those relays the two diodes on each light assembly are potential points of failure. Check everything very closely and methodically.

[Superhawk996]

Question is would a dead or shorted diode cause the up/down observed?

Yes

Let’s say the UP diode (D4) on the driver is shorted internally - allowing current to back flow though the driver side UP diode. That current will backflow on the shared wiring over to the passenger side through D2 (becoming forward biased) and then through the passenger side relay. Now on the passenger side we have forward biased diodes on both the UP (D2) and Down (D1) wires.

When the passenger side motor hits the down position and the rotary switch opens the down contacts it doesn’t matter. The UP contacts are simultaneously closed and there is 12v sitting there ready to go due to the backfeed through D4. This goes to the relay, and the motor cycles up. When the up contacts open, we still have 12v sitting there ready to go on the down contacts. Now the motor cycles down and opens the down contacts and closes the up contacts. But … 12v is still sitting there on the Up circuit (backfeed from shorted D4) and now the motor cycles up again. This will continue until the headlamp is moved to the UP position. At that point the D4 is no longer in play, the backfeed through D4 is removed, and the motor will cycle up, the UP rotary contact will open and the motor will stop and will stay up on both driver and passenger side.

See your modified schematic below:

Red is current flow through the down headlamp switch and through the passenger and driver relay.

Green is the reverse current flow though an internally shorted diode D4 or shorted wiring that bypasses D4. That current can flow over to the passenger side and will forward bias D2.




I don’t believe OP has verified his driver side diodes. This should be done but I know it’s a pain. I was asking him to pull relays one at a time so I could verify the current source to the motor to make sure the short to the motor wasn’t somewhere else other than the driver side diode.

[Superhawk996]

. Back to the original up/down issue, what are the chances that there's metallic build up on the insulator for the down wiper?

Slim to none in my opinion.

Grease and a light metallic debris creating a current path across the non-conductive portion of the rotary switch isn’t likely at all. Would have to be an awful lot of debris and even then, the current flow through it wouldn’t likely support enough current flow to turn on the relay.

Now if there was enough metallic debris built up to bridge the finger contacts directly - yeah that’s a problem.


Per the rotary switch photos - you can see the opportunity for corrosion & debris. If diodes and wiring all check out, it would be worth opening, cleaning and retensioning the contacts. Wouldn’t be the first time I was wrong about something (IMG:style_emoticons/default/shades.gif)

[Superhawk996]

What else could cause the down to skip right through the stop to cycle again?

Shorts in the wiring itself.

I suspect this is the more likely scenario for the OP.

Two problems with my internally shorted diode scenario.

1) Diodes usually fail open. In that case, the up or down function just doesn’t work.

2) When the driver side motor goes to the down position it should open the down rotary switch which itself would keep the current from reverse flowing through to D4. So although the wonky up/down on the passenger side can occur when lights are between fully up/down, it would eventually resolve itself after a few cycles and should not continue indefinitely. For the behavior to continue indefinitely, there would have to be a dual failure of both D4 and the passenger side rotary down switch. Not impossible but not likely either.

[Spoke]

Changed the wheel to look a bit more like the actual unit although still kept the switches on opposite sides for clarity.

All switches now shown in the DOWN condition. The driver side (left) has stopped. The passenger side is cycling. D4 shown shorted.

Not sure I see a way to backfeed to the passenger side without an external leakage path.

[searunner]

What else could cause the down to skip right through the stop to cycle again?

Shorts in the wiring itself.

I suspect this is the more likely scenario for the OP.

Two problems with my internally shorted diode scenario.

1) Diodes usually fail open. In that case, the up or down function just doesn’t work.

2) When the driver side motor goes to the down position it should open the down rotary switch which itself would keep the current from reverse flowing through to D4. So although the wonky up/down on the passenger side can occur when lights are between fully up/down, it would eventually resolve itself after a few cycles and should not continue indefinitely. For the behavior to continue indefinitely, there would have to be a dual failure of both D4 and the passenger side rotary down switch. Not impossible but not likely either.

FIRST, Thanks for HELP
Today I did the Test with and without the Relays
I reconnect the RED wire to the 3 Connector HLight
BATTERY OFF
Passenger HLamp DOWN---------------------------------Driver HLamp DOWN
BATTERY ON
Passenger HL UP & DOWN -continue-------------Driver HLamp DOWN NO Move
RELAY Passenger OFF STOP Movement------------------Driver HLamp DOWN NO Move
RELAY Passenger IN UP&DOWN restart----------------Driver HLamp DOWN NO Move
RELAY DRIVER OFF DOWN NO MOVE-- Passenger HL UP & DOWN -continue- ---------next I have reconnected the relay on the Driver side
CAR KEY ON
-------- Passenger HL UP & DOWN -continue --------- Driver HLamp DOWN NO Move
SWTCH LIGHT in Position Light
----------Passenger HL UP & DOWN -continue ----------Driver HLamp DOWN NO Move
SWICH LIGT turned to KIGH Light
----------Passenger UP stable------------------------------Driver UP stable


I can go on the road with the TWO DAYLIGHTS that are connected with the POSITION light
or with all TWO HLamp UP with SW Light on KIGH Light position -
The Problem is that I must disconnect the Passenger RED wire.
I have the Head lamp passenger UP& DAWN immediately when the BATTERY is connacted.

[searunner]

I hypothesise that if I connect the LOT of the red wire-
With a positive wire from the light switch? What can be the PIN involved??

[Superhawk996]

Not sure I see a way to backfeed to the passenger side without an external leakage path.

When the rotary switch is been full up or full down there is contact & continuity between all three fingers that are contacting the rotary switch.

You can see the contact traces (blue) and in red zones you can see all three fingers will have continuity.

[Superhawk996]

I hypothesise that if I connect the LOT of the red wire-
With a positive wire from the light switch? What can be the PIN involved??

Do not start cobbling up the system.

Far better to troubleshoot and repair properly.

[Spoke]

What else could cause the down to skip right through the stop to cycle again?

Shorts in the wiring itself.

I suspect this is the more likely scenario for the OP.

Two problems with my internally shorted diode scenario.

1) Diodes usually fail open. In that case, the up or down function just doesn’t work.

2) When the driver side motor goes to the down position it should open the down rotary switch which itself would keep the current from reverse flowing through to D4. So although the wonky up/down on the passenger side can occur when lights are between fully up/down, it would eventually resolve itself after a few cycles and should not continue indefinitely. For the behavior to continue indefinitely, there would have to be a dual failure of both D4 and the passenger side rotary down switch. Not impossible but not likely either.

FIRST, Thanks for HELP
Today I did the Test with and without the Relays
I reconnect the RED wire to the 3 Connector HLight
BATTERY OFF
Passenger HLamp DOWN---------------------------------Driver HLamp DOWN
BATTERY ON
Passenger HL UP & DOWN -continue-------------Driver HLamp DOWN NO Move
RELAY Passenger OFF STOP Movement------------------Driver HLamp DOWN NO Move
RELAY Passenger IN UP&DOWN restart----------------Driver HLamp DOWN NO Move
RELAY DRIVER OFF DOWN NO MOVE-- Passenger HL UP & DOWN -continue- ---------next I have reconnected the relay on the Driver side
CAR KEY ON
-------- Passenger HL UP & DOWN -continue --------- Driver HLamp DOWN NO Move
SWTCH LIGHT in Position Light
----------Passenger HL UP & DOWN -continue ----------Driver HLamp DOWN NO Move
SWICH LIGT turned to KIGH Light
----------Passenger UP stable------------------------------Driver UP stable


I can go on the road with the TWO DAYLIGHTS that are connected with the POSITION light
or with all TWO HLamp UP with SW Light on KIGH Light position -
The Problem is that I must disconnect the Passenger RED wire.
I have the Head lamp passenger UP& DAWN immediately when the BATTERY is connacted.

Thanks for the information. Yes you can drive your 914 with lights on. If you have to stop the engine if you change the headlights to 'parking' the headlights will be off and the pass motor will not cycle.

What you observe seems consistent with our thoughts that the pass side relay is not releasing for headlights OFF.

[Spoke]

Not sure I see a way to backfeed to the passenger side without an external leakage path.

When the rotary switch is been full up or full down there is contact & continuity between all three fingers that are contacting the rotary switch.

You can see the contact traces (blue) and in red zones you can see all three fingers will have continuity.

Agreed. In the last schematic I show both UP and DOWN wipers closed when not at 0 or 180 degrees.

For the case of D4 shorted, the pass coil would have the voltage of the driver coil through the driver UP wiper. The voltage of the driver coil is zero as the driver DOWN wiper is open. So the pass coil would be off.

This is why I think that some external (to the schematic) short is happening. Either the pass DOWN wiper is leaking or there's a wire short.

Thanks for the pictures. I've not seen these before. That grease looks really nasty.

[Superhawk996]

So from post #32 we know that removing the passenger side stops the continuous up & down movement of the passenger side.

This tells us:
1) The motor itself isn’t shorting to a 12v source.
2) The motor is sourcing current through the relay as intended.
3) We need to figure out why the passenger side relay is continuously being powered.

To figure out #3:

A) Remove the passenger side headlamp motor relay. Manually move the passenger headlamp to the full down position manually if necessary.

B) Put the headlamp switch in the on position.

C)Use a multimeter to measure the green/black wire to the headlamp motor - should be 12v

D) Use the multimeter to measure in the relay socket - pin 85. Should be 12v. Note: the relay will have the pin number on the case that you can use to find the corresponding socket in the rubber relay socket.

E) Use the multimeter to measure the gray wire to the back of the headlamp motor - should be 0v.

See picture below things in green should be 12v. Blue circle 0v on gray wire

[Superhawk996]

Now do the the same with the headlamp switch in the off position (headlamps down). Passenger side relay still removed.

Now the gray wire should have 12v on it.

Pin 85 of the relay socket ought to have 12v on it.

The green/black wire to the back of the headlamp motor ought to have 0v.

[Spoke]

Good point ! I have cleaned these (internal discs and 'Stylus style) switches inside the headlight motor housings. These can also easily short out/ or conduct erratically >> by deposits of lube grease that drops out of the small gears in there on to the disc's. Weird... but not 'Pasta my trouble shooting capabilities ¡

@searunner

So you had the motor removed and opened the gears to clean the wipers? If these were already serviced, that should discount the wipers from being an issue.

Was there any work done to the front of the car before this occurred?

What did the grease look like? Did you clean/replace the grease?