Vexing Headlight Woes

[REDTAN89]

VEXING HEADLIGHT WOES--UPDATED

With assistance from the helpful contributors to this post I tracked down the 1N4001 Diode that was located on the passenger side of the console. The diode was hardwired to a plug that mated to a connector that included two yellow/black wires and one yellow wire.

As the diode was burned beyond recognition, I deduced that the diode's polarity would probably be FROM the yellow wire TO the two yellow/black wires. I cut the old diode out and wired in the new one. Pushed the headlight switch and....... drivers side went up, passenger stayed down. Hit HEADLIGHTS OFF switch and the headlights reversed. Repeated this sequence three or four times...same results. The LED next to the LAMPS RETRACT switch (under the cassette player) was now lit again (it had gone out with the death of the old diode) but pushing the switch yielded NO RESPONSE whatsover.

Took the diode out and reversed polarity. Result: NO RESPONSE whatsover. LED on RETRACT switch out again. Reversed diode polarity and got the same UP/Down results as above.

I'm baffled. Could I possibly have put the motors back on the wrong sides of the car, and would this cause such a problem? (I did have both motors out at the same time, but it seems like this would have been highly improbably due to the differences in the mounting hardware.) Also, the serial number on the driver's side motor is visible and it ends in "LH", which I'm deciphering as "Left Hand". Left Hand is the driver's side, isn't it?

I'm all out of ideas so let's walk through this scenario: Why don't I just clip the two wires to the out-of-sync headlight motor, reverse the wires and be done with it. At the very least, it stands to reason that this would get the headlights operable from the headlight switch. I can certainly live without a functional RETRACT switch.

Any thoughts??

---------------------ORIGINAL POST--------------------------

I recently rebuilt my headlight motors on my 89 coupe, following the instructions outlined in Barney's fine post on Reatta.net. Before beginning repairs the headlights exhibited the classic symptoms of the failed plastic bushings; they'd strain to raise. Sometimes they'd make it, sometimes not.

I followed the instructions and happily replaced the repaired motors, testing them with a battery charger before finishing the re-installation. Both motors functioned normally in the test, but when I finished installation and hit the headlight switch... only the driver's side headlight went up. I retested with 12 volts from the battery charger and both motors went up and down as I reversed polarity. I manually raised both headlights via the motor knobs and hit the "Lamp Retract" switch on the console. The driver's side went down, the passenger side stayed up. I hit the headlight switch....nothing. I hit the "Lamp Extract" switch again.... nothing. I tested both motors once more and they still functioned normally via the battery charger route.

Confused, I turned to this forum, where it was suggested that the Headlight Control Module might be the culprit for this abnormal behavior. I ordered a used one from Jim Finn and replaced it today, again with the generous advise from Jim and Barney on locating and accessing the HCM. I also replaced the headlight switch module and wiper modules, as the originals were sticking a bit and generally showing signs of age.

When I plugged in the new (used) module the driver's side headlight raised; the passenger side stayed down. I manually raised the passenger side and hit the headlights on switch. The driver's side went down...passenger side stayed up.

I disconnected the battery, thinking that maybe this would "reset" the module. I manually put down the passenger side and again pressed the headlights "on" switch. Driver's side up. Passenger down. Pressed the headlights "off" switch. Now they flip-flopped. Passenger went up, driver down. Pressed the switch "on" again. Flip-flopped again. Driver up, passenger down. Pressed the headlight "off" switch again. Flip-flopped again. Passenger up, driver down.

Pressed the headlight "on" switch again. Nothing. Pressed the "Headlamp Retract" switch and the console. Nothing. Pressed the headlight "off" switch again. Nothing.

That's where our story ends. Headlights are unresponsive via the headlight switch or "Headlamp Retract" switch. Took out the "Fog Lamp/Headlamp Retract" switch out, examined and exercised it, reinstalled it. Still nothing. Battery Charger test still operates both motors as normal.

After dark I tried the headlight switch and "Headlight Retract" switch again with ignition both "on" and "off". Still no response whatsover. I did, however, notice what sounded like a relay clicking from somewhere behind the cassette housing or possibly in the dash on the passenger side when the Headlight Switch was turned on and off with the ignition "on". No such noise with ignition "off".

Another interesting note: When I pressed the "Fog Lamp" switch "on" with the ignition on the parking lamps all illuminated (the fog lamps did not...I believe the bulbs are burnt out) as did the "Parking Light" LED on the headlight switch. I should also note that the "Daylight Sensor" doesn't seem to be functioning, as the instrument panel lights stay on full illumination, even at night, and the dimmer potentiometer has no effect.

So here's my question: Anybody interested in a Car Bash? I'm thinking 3 swings for a quarter with a ten pound sledge.

But seriously, has anyone experienced a similar situation? Anyone have any other ideas? Someone had mentioned a diode hardwired somewhere in the wiring harness as a possible culprit. I'm all outta ideas and would appreciate any help any help any of you might provide.

Best Regards,

Matt

[Barney Eaton]

Thanks for providing such a complete analysis of the problem.

I suspect you have a bad diode. On the 1988-89 Reatta, GM installed the headlight door button on the console. Probably to allow Reatta owners to open their lights when there was the possibility of freezing rain or snow. The doors would be open and not frozen shut, or maybe they thought you needed a way of opening the doors to clean the bulbs.....who knows, it was dropped in 1990.

The diode was placed in the circuit to keep the lights from coming on when the button was used. However Reatta owners have discovered that it causes all sorts of strange problems when it fails. The diode is located in the wiring harness at the front of the console. I believe it is accessed from the passanger side. I have never changed one but it has two yellow/black wires going to one end and a solid yellow wire to the other. It is polorized and you need maintain that polarity when you install the new one.

Other Reatta owners have supplied the following part number from Radio Shack

IN4006 is the preferred replacement.

You could also have a damaged wire running to the passanger side. While it sometimes works, it could be intermittant. You need to inspect the harness from the headlight to the module to verify that is not the problem.

[Vincent Vega]

I'm experiencing a similar problem. For me, the diode keeps burning up. I've gone through three of them. The polarity has been correct. I have not had time to follow the headlamp circuit test in the FSM. [color:"red"] I suggest you take a look at the online doc at reatta.net. They will have a circuit test you can follow to isolate the balky circuit. I don't drive at night very often so it's not high on my priority list. I can plug the diode in, turn the lights on and remove the diode. The lamps stay lit. The last time I did this the diode started burning up before I could pull it. It was hot enough to burn my finger when I pulled it. Like the roof that only leaks when it rains, my headlights aren't a problem until it's dark. <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" />

The Diode can be accessed by removing the console cover on the passenger side. As Barney mentioned it is connected to yellow\black wires. It may be covered up with black tape. My 88 has the diode in a regular male connector(black) that plugs into a female connector(white/clear). To replace the diode I used basic spade connectors (red) crimped to the new diode. I then plugged them into the female connector. When mine burn up there is a very strong burnt electrical smell.

[REDTAN89]

Thanks for the replies.

Regarding the : [color:"red"] "The Diode can be accessed by removing the console cover on the passenger side."

What/where exactly is the console cover? When I had the cassette assemby and Fog Lamp/Headlight Retract Switch Module out there were a couple of wiring harness ends visible? Could the diode wire be in one of those cable bundles?

Are you possibly referring to the carpet covered Fuse Box Access Door, or does more of that side of the console come off. (I've left the Reatta at another location and can't examine it at this point.)

Thanks so much.

Matt

[Vincent Vega]

I'm referring to the entire carpeted panel on the passenger side. You will need to move the seat all the way back. It is held in place by T-15 Torx screws. When the panel is removed you can see the entire "relay center" The yellow/black pigtail is loose wires (not clipped to anything). Just right of the relay center.

[Guest kennyw]

Also, sorry to inform you that the led's you mentioned are NOT led's but what shines through from an El.Lum.110 volt board. The light sensor is bad, center of dash under the grille and should solve the dimming of the dash, ctr, at night and what I call tell-tale-lights on all of the controls. If the tell-tales fail to light, it is off to the 110-volt inverters. There are 2 of them......ken

[Shelby]

I can help car bashing equipment.

Pick from the list below.

Fix the diode and enjoy your car.