hey everyone

I am having an issue with the drivers side headlight motor on my '85

- passenger side appears to work fine - lights on up and down on command

drivers side light works no up or down

will open with turning the **** manually
had just changed all new relays after issue (not the brightest move but oh well)

was looking at the fsm to try to see if i can decipher the witchcraft used to create automotive circuits

removed the relay to check the connections red was constant 12v, yellow 12v when lights on, 0 when off, black 0 all done with ignition switch off

next connector - white and dark green - both tested 12 v without anything on - that did not seem right nor was it according to the book - unless i am reading something wrong and or doing something wrong

i checked these with the relay unplugged from these connectors - so is that the way to test that or did i do something wrong or are my green and white wires messed up?

if i am supposed to leave the relay on for the test - how does that work

very confused on this

any help would be really appreciated

Sean

 

I have an 87, so this is my take. Headlights always have power to the switch, headlight motors on my 87 always have power to the motor. It is the job of the limit switches inside the motor to break the power and stop the motors movement. On my 87 this is done by the motor shaft being able to slide back and fourth in copper bearings and limited by springs. When the headlight hits the stop the motor (using the gear) screws itself forward (or backward depending on opening or closing) and a block on the shaft of the motor pushes the contact open. When you push/pull the headlight switch in the oppostite direction, the voltage is applied to the other arm/contact and the motor spins the headlight until it hit the stops and the the shafts pushes itself (compresses the spring ) and opens the other contact. If you have the battery connected on a good motor and manually move it you will move the block and close those contacts and the motor will move (watch out for your safety when moving headlights manually as than can move very fast and your arm will be the receiving end of pain!) In other words, on my 87, the switch to turn off power to the headlight is inside the motor, the movement of the motor pushes one of two arms with a contact on it and opens the circuit, then push the switch in the other direction and it moves until it pushes the other arm and opens that contact. The shaft of the motor is set on springs, it moves within it's mount back and fourth about 1/4 of an inch to mechanically push those limit switches open. On the shaft of the motor is a black block, as the motor compresses the springs so it can move, this small block, which is in between the arms of the 2 contacts, pushes one open to stop the motor. It is a combination of the switch and the relays to swap polarity on the motor and run it in different directions. The two tabs I have circled on the first pic are easy to break, the block on the shaft has to be accurately placed between these tabs during re assembly or they will break, just make sure you place the block in between the two tabs before pushing motor shaft back into housing.

The two problems I had were the 2 contacts had carbon buildup, and the arms the contacts were mounted on had over the years bent away from the block and it could no longer reach them to push them apart and stop the motor, the grease has also become hardened. If you try to follow the logic of the relays you will go bonkers. It is basically like this, the motor shaft moves a small amount, the black block mounted on the shaft pushes the contacts open and stops the motor, when you push the headlight switch in the opposite direction the voltage comes in on a the other contact and the motor screws itself until the headlight hits the stop and shaft moves appx 1/4" and pushes open the contacts, these motors always have power to them unless the battery is disconnected. Because my headlight was cycling from the thermal breaker, it burned out the relay as well.

You are not removing power from the headlight motor when you turn the headlights off, you are simply powering the motor in a different direction until the block can push the contacts open. The light, yes, power is removed from the light, but not the motor. If the block is unable to push the contacts apart when the headlight hits the stops, it will begin to draw high current, the little glass thermal circuit breaker will heat up, bend, and open it's contacts, 7 seconds later it will cool down and cycle again.

I will try and find my images,
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The shaft moves, the block riding in between the the tabs (The tabs keep the block on the bottom) hits the contacts arms and opens the circuit, I know I am am redundant, I always have been. If you dissassemble this make sure springs are not bound up and the shaft can move freely. Also, 2 red tabs will fall off when you open the motor, they fit on the opposite cover and hold down the square copper shaft bearings, notice there position when you pull the case apart.

On the pic below the large gear has been removed. Troubleshooting the relays taught me that a digital meter can read source voltage because it is sensitive but the current available may not be enough to run the appliance, in other words you might see 12v on the meter but a burned contact may not have enough surface area to pass enough current to move the motor.
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thanks - that is mind numbing for sure - it is one of the reasons I started considering a different set up - i was looking at an upgrade that is offered to change to a module from a later set up and motors from i think it was 2000-2004 - and module 1988-2004 i believe. https://www.zip-corvette.com/84-87-h...t-car-set.html

not sure if that solves much

I will try to re-check things tonight before disassembly - but yes i wondered about the 12v still not getting enough to actually move the door - i will try -carefully - to move the door again - the first time it did not jump into action when i was turning it and battery was still connected- much more to look at perhaps

 

 

thanks again for the great images and explanation - it is an enormous help!

 

ok so with everything plugged in tried the manual open the door light switch off - door almost open 2/3-3/4 of the way - motor closes the door
with the light switch on - i can manually open the door completely - the motor does not try to do anything -

thoughts? - limiter switch inside motor? (heard someone mention that as an issue in another situation)

 

so power to close ok power to open - not so much

 

with light on green has 12v gray does not - going from relay to the plug that connects the motor - there is power to relay red, yellow and green as mentioned above -

i thought the gray would have 12v also? - or is that with lights off -

 

CAUTION , I do not have an 85 service manual, so I do not know your exact wiring. My system has 3 wire motors. Green white and grey.

Unplug the the motor, jump 12V and ground directly to the motor and see if it moves both directions. BUT CAUTION these motors are strong and fast, make sure you are out of the way and ready for it to swing.

test 1 .....grey+12V , Green-ground

test 2.... Green+12V , White-ground
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thanks - I will give that a try tonight - last night was the first time the motor reacted that way - it sounds a lot like what you were describing - wires and colors sound the same as mine - I know there were changes over the years but those colors and alignments sound the same -

 

Also, while your in there you can clean up a couple of grounds, on the right side in front of the coolant overflow tank on the frame and on the left side same place on left frame in front of relays. I have a rule that if I find a ground all work stops and the ground gets cleaned up.

 

definitely - can't seem to get to all of them or clean them enough - I always try to clean any and all connections when possible -

 

not sure i got a great connection - i am going to try again later - lights on or off when i made contact as you described - nothing happened either time - so i will try to make another jumper wire to test again

 

STOP, You need to understand this, I apologize if you are saying "lights on or lights off made no difference", That you meant jumping/reversing the wires directly to the plug, it sounded as though the light switch is somehow still in the equation.

UNPLUG the motor at the headlight. There are two connectors, one for the light and one for the motor, we are taking the headlight switch and the entire car out of the circuit. You are going to run the motor strictly by 2 jumpers straight from the battery's 2 terminals. The headlight switch at this point has nothing to do with it, you will have 2 wires from the battery directly to the connector on the headlight. If you are not electrically familiar you will want to ask a friend who is. But again, My apology, you probably just meant reversing the wires to open and close the headlight.
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gotcha - thanks my misunderstanding - re-try tonight - no switch - just battery - made a new jumper wire should work fine

 

Remember it is 2 jumper wires, 1 for negative and 1 for 12V.
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Now, if you use a meter you can check the male side of the connector that goes back to the relays, with the connector unplug, this is where you find these voltages. The relays are changing the voltage and the ground from pin to pin so it can reverse the motor in the other direction.

Headlight doors close = grey12v - green ground

Headlight doors open = green12v - white ground
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tried again - no response - checked wires i set up and when connected to battery they are showing 12v - when touching them to the gray and white or green and white no reaction could that be a problem with the wire to the motor?

 

Look at the chart above or look at the 2 pairs I spelled out for you. Grey and white are never used together. My suggestion is to get someone to help you that understands electricity.