Reatta in Germany - Headlight problems

[Aztec62]

Hi once again,

I have a strange problem with the headlamps:

I have rebuild both motors with an overhaul kit. On both motors the rollers had turned to plastic dust.

After installing the motors together with new (european style) H4 lamps, only the left headlamp pops up.

The right side lamp does not move at all.

Both lights switch on and off. A different headlamp module did not help, the right side stays closed.

Jump-wired the right motor to 12V DC: Motor moves headlamp up and down.

Checked the voltage signal on both sides with a digital voltmeter. Signal looks the same.

I know it is a pulsed signal, I will still have to check with a  scope.

But for now, I am stuck.

Anybody can help?

[droid5977]

Have you replaced the bell crank arms that open and close the headlights? There are vendors listed on this site that have a redesigned arm that doesn't strip out like the originals.

[Aztec62]

droid5977,

Yes, I have installed the full overhaul kit on both motors, including the bell crank arms.

Thanks for your help.

[Ronnie]

I would try installing stock bulbs in place of the european style H4 lamps. The door control module is sensitive to current draw by the headlamps. Without enough resistance the doors won't open or close properly. Also when the doors are trying to open try turning the manual knob to help them open. It's possible you have a bad place on the armature of the motor.

[Aztec62]

Ronnie,

I still have the US "Sealed Beam" headlamps. I will install these and see what happens.

Unfortunately, these are not leagal over here, hence the swap to H4 lamps and bulbs.

 

I have noticed that, without the bulbs installed, the headlamp door stays open and wont close.

Wth the bulb removed (infinite resistance sensed by the headlamp module) the headlamp door will allways move to the open position, also for example from an intermediate door position.

The door should only close with an intact light bulb installed.

According to the workshop manual, this is an automatic feature.

It makes it easier to sense and replace a burnt bulb.

This feature works on the left side on my car, but not on the right.

The right side will not open, even with light bulb removed.

 

So, I fear the swap to US lamps will not make any difference. But I will try.

 

 

 

 

 

Thanks,

Henning

[Ronnie]

It's hard to say what will happen. I hope it works for you. I would try helping it with the knob first.

[Aztec62]

Agreed.

In case turning the knob helps, I will need a new motor :-(

Well, hopefully not...

 

Henning

[2seater]

I had a binding issue when I rebuilt my motors. The end play for the shaft that spins was bound through my own fault on one motor. The endplay is set with the screw and locknut on the backside of the motor, opposite the hand knob. There should be a slight play in and out when you push/pull on the hand knob when the motor is in mid travel (not bottomed at either end of travel). The headlight module is current sensing so perhaps it never gets a chance to move before the other headlight comes up? I do believe the wiring is in series from the module to the left and then on to the right.

[Aztec62]

Here is what the manual (1991 Reatta) has to say about how the system works:

 

 

 

[Ronnie]

Thanks for posting the information about the operation of the '91 headlight motors. I had always assumed the operation of the headlight motors for all four years was the same but that might not be true. The '88 and '89 models description of operation (below) isn't exactly the same. It's possible they operate the same and only the description has been updated. It's a little hard to tell.

[2seater]

Yes, I did mis-speak. I am pretty certain the headlight bulb wiring is in parallel but it has a common junction at the left side headlight. I am not certain about the motors. By the way, I run Hella E-code H4's and have no issue with the lights or the doors.

[Aztec62]

Whoever figured it out at GM must be a genius. I have been sitting over the wiring diagrams for the Reatta headlights and doors motors for an hour and I am still unable to explain how the check of the headlight filaments by the door module works.

Must be some ground loop trick.

Plain magic.

---

Thanks for posting the information about the operation of the '91 headlight motors. I had always assumed the operation of the headlight motors for all four years was the same but that might not be true. The '88 and '89 models description of operation (below) isn't exactly the same. It's possible they operate the same and only the description has been updated. It's a little hard to tell.

 

Ronnie,

I have been reading somewere that the older door modules sense the motor current while the newer modules sense the voltage produced by the motors when the pulsed voltage from the module is low.

The spinning motors then act like DC generators for a very short time.

They do not stop spinning instantly when voltage from the module is low.

The down or up coasting movement of the door keeps them spinning until the voltage is pulsed high again and the door continues to open/ close.

I guess that is the reason why the headlight doors are made of alloy and not of pressed steel.

This makes them a little heavier (= more momentum) which helps the down/up coasting movement of the door.

No DC voltage from the motors means motor stopped turning because door is open, closed or jammed.

The module will then switch its voltage off.

 

It sounds to me like it is a smarter, more sensitive way to check the door position than sensing the current.

It might put less stress on the door linkage, gears and on the motor.

 

Again, a work of a genius at GM. Hard to believe how much technology sits behind a simpe headlight door open/ close feature.

 

Henning

[Ronnie]

Did you try helping the motor start by turning the manual knob to see if that made a difference? All the theory behind how the module works is over my head.

[Aztec62]

Ronny,

I am on a business trip in Poland.

Working on the Reatta will have to wait untill the weekend.

 

Henning

[2seater]

I do believe the modules are different both in wiring and method of operation. I had a module that was supposed to work on an '88-'89 and it would not work on my '90. I do know that the module does look for ground through the headlight filament and that must be present to bleed off residual voltage for the door to close. They will not work with LED headlamps unless an aux. headlight power harness with relay is installed and the relay coil acts as the ground.

[Frogware]

They will not work with LED headlamps unless an aux. headlight power harness with relay is installed and the relay coil acts as the ground.

 

Yeah my lower mile 90 has the led's. The guy I bought it from told me that it took him several weeks to figure out how to make everything work. It is a mess!

The doors open and close normally but there are wires stringing all over the front end and I can't even begin how to trace what he did. For now I am leaving it the way it is but later I will either tear them out and revert back to OEM headlights or fix his wiring mess.

 

It is all a mystery.... :huh:

[2seater]

Daves89 installed an aux. power harness that is designed for taking the load off the headlight switch, critical on the early '90 models, but it has an extra benefit in that it allows the LED headlight conversion to operate normally. The added power isn't needed with the LED, but even stock sealed beams will benefit if reinstalled. Maybe Dave will chime in with the details.

[Aztec62]

Hi,

 

I had a closer look at how the door module senses an operational headlight bulb to close the doors.

Here is what I have found:

First, this is what it says in the workshop manual (90 and 91 Reatta have the same text):

 

[2seater]

I believe the ground shown is indirect since it is through the lo-beam filament, not direct to ground. As far as I remember it described several years ago when I was doing a headlight wiring upgrade, it functions as a drain wire when unpowered.

[2seater]

There was a giant thread from 2013 over on the AACA Reatta forum about the headlight doors not operating properly after adding relays for headlight power. I read through some of that thread again to refresh my memory but there were a couple of comments that may have some bearing: the 88-89 module will not work in a 90-91 and there was some speculation that they carried the same part number? The other item was that the door motors were operated independently within the module. I do not know for certain what the pulsed signal may be? As far as I know the module just does a reverse polarity of battery voltage to operate the motors. That yellow wire in the diagram is the magic wire that can be B+ or the drain wire to tell the module to close the doors.