newbecorvetteguy

Energize one side and ground the other, motor runs one way. Reverse that and it runs the other way. What's the third (center) wire for?

Demonic85

Uhhh, I think it controls the advance on the motor. not sure though.

red_johnny

Stab in the dark...maybe a sensor to let the headlight motor know it needs to stop?

newbecorvetteguy

Here's why I'm asking. My right side motor quit last November...closes fine, won't open again once closed.

Bought a new one on ebay a few weeks ago. That one worked fine for two weeks then seemingly stripped a gear. GRRRRR. Got to get a hold of that guy to see what he wants to do. It's a corvette parts place.

Anyway, If I energize the two outside leads on the old motor (the one that closes only), it runs one way. Reverse polarity and it runs the other way. Since the new motor runs both ways as it should, and I can jumper the old one to run as it should, I suspect the problem with my original motor has something to do with that center wire.

This car hates me. Yesterday on the way to work it was making god awful sqweeking, grinding and poping sounds (day before it was just sqweeking a little) which turned out to be the outer u-joint on the left half shaft. Took the day off today to fix that, but ended up getting it done last night after work. That job was a breeze thanks to this forum. When done, I took it out for a test drive. It was getting dark so I turned on the headlights. Came on fine. Drove around for a while, all was well. Got home, turned off the head lights and the one I just replaced hops bounces and grinds and never stops. #$%&!!!?

c4cruiser

Here's the wiring diagram for an 86. Might help trace the leads and what they do depening on the polarity they see.
http://members.shaw.ca/dankai/Headlight%20Doors.pdf

MrRenoman

If the motor was freewheeling then, yes, the motor will spin in the opposite direction if you reverse the leads. When the motor is installed in the frame and and the frame is allowed to hit the stops then the torque induced on the motor causes the motor inside, sometimes called an armature or rotor, to move/slide linearly in one direction. This sliding causes the internal limit switch to open and/or close a set of contacts. If you tried to reverse the polarity on the same two leads after it hit the stops then the motor won't turn in the opposite direction. It requires that the voltage be applied to the third lead and one of the other two. It's an odd setup. Even if you look at the schematic it's a little confusing. If you look at it you'll see 2 arrows that indicate the path the current takes through the motor. When torque is applied to the motor, when it hits the door stops, the limit switch moves to make contact with the other leads (the arrows flip along the dotted lines) changing the current path. In order for the motor to turn in the opposite direction the current has to flow in a different path. Thats what the headlight relays do. It gets even more complicated when you add the third relay. It's a puzzle to figure out what's happening when the light switch is on, off, what the relays are doing and what the limit switches are doing every time the headlights rotate to the up and down stops. Something else to keep in mind is that the relay contacts close immediately when power is applied to them. The healight limit switch contacts, on the other hand, don't move to change the current direction until the motor completely rotates and hits the stops. If you have an electrical mind you can follow what is happening. Confusing ain't it???

Art

jfb

The headlight motors have three wires. One wire (green on the LH door and green/white on the RH door) goes to a circuit breaker and then one motor winding. The other two wires each go to a contact that makes connection to a moveable arm that goes to the other motor wire and the connection is made when the headlight door gets to its full open or its full closed position which sets the circuit up to close (if open), or to open (if closed) when the headlight door relay is energized (if door is closed) or not energized (if door is open). You cannot open and close the door by jumping 12v to one pair of wires (leaving the third alone) and then reversing polarity on those same two wires.

newbecorvetteguy

Thanks for the info and the wireing diagram. Hopefully it does me some good.

Don't know what you're telling me jfb. I've been able to spin both motors on and off the car using the two outside wires only. That's why I was wondering what the center wire does.

MrRenoman

Off the car the motor should run in both directions when you reverse the outside wires. Once installed on the car and the motor is allowed to hit the stops then it shouldn't work if you reverse the wires. That is, if the motor actuator is working properly. If it isn't working properly and the limit switch isn't moving to change conductors then it's possible the motor could operate by you reversing the wires. This could be the very reason why the lights don't close like you mentioned. This is because the relays are trying to apply voltage to the other two leads that are supposed to be connected to the motor armature. If the limit switch isn't working then the headlight won't close. Dirty limit switch contacts are what I have experienced as being one of the reasons for headlights not working. As you mentioned, the new motor runs in both directions because the gears are strip and the housing doesn't get a chance to hit the stops which would cause the limit switch not to operate. You may try disassembling your old motor and clean the brushes, armature, and limit switch contacts. It's worked for me, at least until the brushes wore out completely after 160,000 miles.

Art

newbecorvetteguy

Thanks everyone. Did what you did before Art, without success. Of course I was trying to use a nail file before. Rumaged around my tool box and found my points file that I probably hadn't used in 20 years. Took the motor apart again and filed on those contacts with the points file for a while, plugged it in and it worked fine. Been good since. Hope it lasts. At least I know how to test them now and where the likely problems are. Thanks again. Reading you guys' posts is better than taking a class.

MrRenoman

Yogivette

Ok guys im tryin not to start a new thread. My pass. side headlight works fine for the time being. The driver side does not. When i turn the headlights on they both open and lights come on. When i turn them off only the pass side closes. Therefore the drivers side stays on.

Sounds like i have a problem with the limit switch as per Mr. Renoman. If this is indeed my problem can someone give me or point me in the right direction to get some directions on how to fix/clean this. I looked at the wiring diagram but im not one to follow exactly how it works. If you could explain the simpler the better. I understand electric currents and switches just not how the actual light assembly works. Thanks for the help on fixing my problem. First lets start, is the problem in the motor assembly or relay assembly? Thanks.

MrRenoman

Your profile shows you have an '86 so I'm assuming that's the vehicle you're having the trouble with. To ensure that the problem is not in the relays or light switch I would check the voltage and polarity at the connector. To do this you need to unplug the motor from the engine harness. The systems powering of the motors is complex. The relay output power and the position of the limit switch in the motor combined cause the headlights to open and close. Another simpler method is to attempt to rotate the headlight motor **** when it is stuck in the up or down position. When the headlight is stuck up or down, open the hood, and try to turn the headlight ****. If the motor suddenly runs then the power going to the motor is fine. If turning the **** doesn't work, then try closing the hood. Dropping the hood about a foot may cause enough vibration to cause the headlight to open or close. Try these methods first. Also, when trying to rotate the **** or when dropping the hood, make sure the headlight switch is on or off depending on which direction you want the headlight to turn. Off to close it, or on to open it. If the headlight motors still don't turn, then uplug the motor connector from the engine harness. Probe the 3 wires while the headlight switch is in the on position. If the relays are working properly then +12VDC will appear on two of the three wires. Note the colors of the wires the +12VDC appears on. Next move the headlight switch to the off position. You should not see any voltage across the same two leads. Now probe for voltage across the three wires again. If you find voltage across two different leads, note the colors of the wires the +12VDC appears on. If you notice that one of the leads is common between both tests and the polarity reversed on that one common lead, then the relays and wiring are working properly. Explaining it this way is easier then trying to explain it while looking at a schematic. You can also try applying 12VDC to any two of the three leads going to the motor once it's unplugged. If the motor is working properly, you should be able to see it rotate to the up position or the down position depending on which two wires you hook the voltage to. If the motor does turn on any two leads leave the power on the leads so the motor fully rotates fully to the open or closed position. When the motor rotates to the stops the torque induced on the motor causes the limit switch to move inside the motor. The voltage and polarity of the power required to move the motor in the opposite direction and to the stops is on two other leads. Don't worry about which two leads you are putting the power to. Just try every combination of power to two of the three leads including reversing the polarity of the leads. Make a note of what color leads you tried to put the power on and the polarity. Let me know what you find.

Art

Yogivette

Thanks I'll try that at the motor plug...the motor def. is not turning the headlight when using the manual ****, i have to manually put it all the way in. Also ive tried with someone pushing on the headlight a little and that doesnt start the motor so i think it might be one of those relay/3 wires. I'll report back.

MrRenoman

I didn't want to suggest pushing on the motor housing but since you already tried it and didn't work, that's good to know. I've used pushing down on the headlight assembly to torque the motor. That worked for me when mine was on the blink. In my case it was the motor brushes because the car had 170K miles on the headlights and the brushes just wore out. If you have considerably less mileage it could be in the relays but you should test the voltages at the harness connector when you unplug the motor to isolate.

Art

Boat28

I have read the posts about headlights staying open. All I did was put in gear .put back together turn on lights ,and they opened. Lights go off with switch but lights stay open. Did get it out of adjustment?