I posted last week with my right headlight problem. I am gaining ground on it but still have'nt got it working. When I turn the lights on the left one opens & the right one does not. I can hear a click in the motor every few seconds. If I unplug it & open it manually & then plug it in, turn on the lights, the left one opens & the right one closes & then the clicking starts again. I did do the test with a battery & some test leads. I can open it & close it by jumping the prongs in the plug. So the motor & assembly must be OK right ? I also switched the 2 relays with the same results. The only thing left that I can see is the isolation relay. Does anyone know where to get one of these. I can't find them in any catalog. It has a different # than the 2 other relays & it appears to be a bit smaller in size. I need more ideas what to try next if anybody has any.....Thanks for the help so far

 

The Isolation relay is only used by the passenger side headlight motor to close the headlight door. It does not play a role in the opening of the passenger side headlight door.

On the relay socket of the passenger side door relay the wire colors are Yellow, Red, Black, White/Black and Dark Green/White.

Do you measure 12 volts on the Red wire which is hot at all times?

If that checks out try this.

*****Disconnect the headlight motor plug on the passenger side.****

The motor has three wires.
Dark Green/White
White/Black
Red

With the door in the closed position, using an ohm meter you should measure the following at the motor plug.

Zero ohms from the Dark Green/White wire to the White/Black wire.
Open from the Dark Green/White wire to the Red wire.

If that checks out, manually open the passenger side headlight door to the full open position. You should measure the following.

Zero ohms from the Red wire to the Dark Green/White wire.
Open from the Dark Green/White wire to the White/Black wire.

 

Thanks, Hooked on Vettes. Depending which scale I use on my meter, I get 1 ohm on the 200 ohm scale & 0 ohms on the 2K scale both the door open test & the door closed test. If you mean continuity when you say open from dk grn/wht to red & open from drk grn/wht to wht/blk, I do get a continuity reading in both tests also.

 

Open meaning (No continuity). Just like if you turn your meter to ohms and the meter leads don't touch anything.

 

I'm not sure you're doing the test properly. Since your driver side headlight door motor is working properly try this and post the results.

The object of the test is to determine if the switches inside the motor are in the proper position when the door motor is in the open and closed position.


**** Disconnect the driver side motor plug *****

With headlight door closed use an ohm meter and measure across the plug going to the motor.

Zero ohms from Dark Green wire to White wire
No continuity from Dark Green wire to Gray wire

Manually open the headlight door all the way open.
With door open

Zero ohms from Dark Green wire to Gray wire
No continuity from Dark Green wire to White wire

 

If it's not a mechanical problem like a stripped gear which is often "not" the problem then it could be a relay problem which is often "not" the problem. It's often just dirty contacts in the headlight motor housing. I'm not saying it couldn't be a relay, it could. I've detailed a way to test the relay circuit later, but first...These motors operate using 3 wires. It's really difficult to explain how the circuit works but I'll try. Most motors use 2 wires and most often all that is required to reverse the direction of the motor is to reverse the polarity on the wires going to the motor. Not with these 3 wire motors. Depending on whether the motor is moving in the open position or the closed position, current flows through 2 of the 3 wires and not the same two when it's moving in the opposite direction. In a properly operating system...when the headlights are closed, and the motor is unplugged from the harness, there should be continuity or zero ohms between the green and white wires going to the motor. If you plug the harness back together and the headlight switch is turned to on, battery voltage or +12 volts is applied to the green wire and the white wire is grounded by the headlight relay. You should be able to test this by probing into the connectors when they are plugged back together. It's the same for both sides. As the headlight motors rotate and completely open and hit the stops an internal switch, a limit switch, in each motor opens the green to white wire circuit in the motor to stop the current from flowing, which stops the motors. At that same moment the internal switch opens the green to white connection it connects the green to grey wire internally. So in a properly operating system, when the headlight doors are completely open and you disconnect the harness you should have continuity or zero ohms on the green and grey wires now. If you plug the connectors back together you should have +12 volts on the green wire and a ground on the white wire. You can test this with a meter probing the connectors. When the headlight is switched to the off position +12 volts is applied to the grey wires and the green wires are grounded by the headlight relays. You can test this by probing the connectors with a meter. If your headlights aren't rotating properly and you don't get the continuity mentioned when the harness is unplugged from the motor then the limit switch contacts are probably dirty inside the motor. This is a very common problem. Many owners start replacing all the relays, spending lots of money, only to find out the problem is still there. This why you shouldn't just reverse the polarity on the headlight motor wires to test the motor. In nearly all cases reversing the polarity on 2 of the wires will rotate the motor open and closed but that's not how the system operates. When the headlights are opening the green wire has battery voltage, in the closing direction the green wire is grounded. Also, manually rotating the headlight to the open or closed position may not exert enough torque on the internal limit switch. With the headlight motor harnesses unplugged, and you really force and turn the **** when the motor is hitting the stops whether in the open or closed position, only then may the internal switch switch the wires where you might be able to measure for zero ohms on the wires.

Another way to test your headlight motors and limit switch is to turn the headlight switch on or off depending on which direction it isn't working, then try turning the **** on the affected motor one way or the other, if you feel resistance in one direction then turn it harder then turn it the other way. If the motor suddenly starts to rotate it will surprise you and twist the **** out of your grip. This is usually a good test of the motor armature and limit switches that are just dirty and not completely worn out. Removing the motors from the housing, dismantling the motor, and cleaning the contacts usually fixes the problem. I can provide a link with pics on how to do this.

If you want to test your relays then unplug harnesses at the headlight motors. When the headlight switch is off there should be +12 volts on the grey wires and ground on the green wires. When you turn the headlight switch to on there should be +12 volts on the green wires and the white wires should be grounded. Again, this is with the headlight motors unplugged and probing the harness going toward the relays. If you get the results mentioned then your relays should be working ok.

The relays connect the motor's green wire to battery when the headlights are opening and the green wire to ground when it closes. The relays also ground the white wires when the lights are turned on but isolates it when they are turned off. They don't really reverse the polarity of the wires, they just redirect them. The only way the motors will operate is if the motor has continuity to the corresponding wires when they are in the completely open or completely closed position. When the limit switch contacts in the motors is dirty then the circuit is not complete, it's open, regardless what voltage or polarity is applied to the motor wires.

I hope this helps and I explained it good enough. I pulled the information from the service manual and I'm very confident the info I provided is accurate. I apologize for any errors. Someone may point one out too. Not everyone agrees that motor problems are only limit switch related. I've worked on these cars a long time and have fixed several of them by just cleaning the motor contacts inside. Sorry for the long post but I'm a detail nut. Good luck.

Art

 

Thanks Art, I have done the manualy open thing where all of a sudden it spins out of my hand. Scared the hell out of me ! So what is the clicking sound I hear in the left motor when I turn on the lights & the right one opens but the left just clicks every few seconds ?
I really appreciate the trouble your going thru with this. Thanks for the procedure you posted. I won't have time today to do the tests but will let you know when I do & give you the results. Thanks again

 

If the manual thing is working then the relays are probably good. What I mean is, the headlight will open or close with assistance which causes the motor to rotate in the direction which the headlight switch is trying to act upon it. As far as the noise goes, this is just a guess...The clicking thing may be due to the high resistance caused by the dirty contact surface of the armature or the limit switch and current is trying to flow through the motor momentarily causing it to want to turn or move but it won't because of the high resistance. There may be just enough contact where the motor is trying to turn or there is some torque being applied to the motor. It's hard to diagnose without hearing it. While it's doing this can you turn the **** to cause the motor to suddenly work. If so, then that's what's probably causing the noise. There is always voltage to applied to the motor whether the headlight switch is on or off. If the limit switch has not opened the circuit when the headlight motor rotates and hits the stops then current is still trying to flow through the motor. This can often lead to a dead battery because the limit switch has not opened. The symtoms for these early motors are different from the later motors which hasn't been brought up in this thread. Don't confuse the symtoms of worn out bushings and motor noises associated with the later motors with the symtoms of the early motors. I wouldn't rule out bad gears but until the problem is isolated to the motors and the motors are dismantled you won't know if it's gears or dirty contacts.

Art

Art

 

wow i guess im gonna have to check mine too, my pass headlight does nothing, i have to manually open and close it drivers is ok, i get no clicking or anything

 

OK Art, I took the motor apart again & cleaned the contacts. Put everything back together. As soon as I plug it in to the harness it opens & does the clicking thing. I did notice when I had it apart, along with the brushes & the contacts there is a little glass tube with wires going into it. It appears dark on the end like its burnt & I'm sure this is what the clicking sound is coming from. I don't know what this is but must be some sort of overload protection. I pluged the assembly in to the left side harness & it does the same thing. I wish I had another motor to try but I guess I'll have to bite the bullet & buy one. I don't see any other solution now. I really appreciate your help tho. You gave me alot of useful info on this......Thanks again