1970 300 Concealed Headlamps

[Waggy]

I have a 1970 Chrysler 300 with Concealed Headlamps and I would like to re-wire it, so I need to understand how they work. I have disconnected the motor leads and I thought when one lead had power, that it would cause the unit to open and if I connected the battery to the other motor lead the unit would close. There is a limit switch that stops the motor. I was reading the manual and got confused! It said for testing, connect the battery to the motor leads at the terminal (NOT the ground terminal), so is the unit grounded through the frame, like I thought or is one of the 2 lead wires the ground wire, if so, why do I need to worry about the ground terminal?
I had planned to run power from the large ignition on wire I have installed, thought a fuse and into a relay. Have the low beam lights trigger the relay to open the headlamp through one lead wire and then when I turn the lights off, the relay would close that lead and send power to the second lead and close the headlamp. It says "Do not bench test, so I do not want to play around.

 

[Davea Lux]

I have a 1970 Chrysler 300 with Concealed Headlamps and I would like to re-wire it, so I need to understand how they work. I have disconnected the motor leads and I thought when one lead had power, that it would cause the unit to open and if I connected the battery to the other motor lead the unit would close. There is a limit switch that stops the motor. I was reading the manual and got confused! It said for testing, connect the battery to the motor leads at the terminal (NOT the ground terminal), so is the unit grounded through the frame, like I thought or is one of the 2 lead wires the ground wire, if so, why do I need to worry about the ground terminal?
I had planned to run power from the large ignition on wire I have installed, thought a fuse and into a relay. Have the low beam lights trigger the relay to open the headlamp through one lead wire and then when I turn the lights off, the relay would close that lead and send power to the second lead and close the headlamp. It says "Do not bench test, so I do not want to play around.

The unit is grounded thru the ground terminal on the case. Your neg battery lead should go there. You are correct about the function of the other two leads, one will cause the headlights to open and the other will cause the headlights to close. You can test the function of the unit with the torsion bar to the headlight doors installed and the unit bolted down. Disconnect the plug with two wires from the motor and hook an alligator clip to the positive battery cable and hook the other end to one of the two wires going into the motor. If nothing happens, try the other lead to the motor, the headlights should open or close. Once the headlights have opened or closed, the other lead to the motor should now be active to reverse the motor direction. If nothing happens with either lead, the motor has an open circuit because of a bad limit switch or defective windings. Bench testing is not recommended because the limit switches may not stop an unloaded motor in time to keep from breaking the nylon gear or the gear cover, they are both on the weak side.

The light switch has a dedicated terminal to operate the relay. There are two power connections to the stock relay, one from the ignition and the other from the light switch. With the light switch in the on position and the ignition key in the on position the relay is active and power is supplied to the motor to open the headlight doors via the active contacts in the relay. With the light switch in the off position and the ignition on, the relay is inactive and closes on the second set of contacts that direct power to the motor to close the headlight doors. If you are going to use an after market relay, it needs to be the two pole type or the headlight motor will not function properly. The stock relay is a pain in the butt to get at as it is located above the park brake pedal on the A-pillar. I would test the relay before pulling it out.
You can test the relay function with a test light. Turn on the light switch and the ignition switch. Hook the ground terminal of the test light to a good ground and hook the probe to one of the wires of the disconnected two wire harness that would normally go the the headlight motor. One or the other of the two wires should have power. Now turn off the light switch, the other wire should now have power. If this happens, your relay is good. If there is no power to either lead of the harness, your may have a bad light switch or the relay may have failed. The light switch has an internal circuit breaker that sometimes fails. If you have no headlights shining behind your closed headlight doors, the headlight switch is bad. I do not think it would be necessary to rewire the circuit unless you are sure it is faulty.



Dave

 

[Big_John]

The unit is grounded thru the ground terminal on the case. Your neg battery lead should go there. You are correct about the function of the other two leads, one will cause the headlights to open and the other will cause the headlights to close. You can test the function of the unit with the torsion bar to the headlight doors installed and the unit bolted down. Disconnect the plug with two wires from the motor and hook an alligator clip to the positive battery cable and hook the other end to one of the two wires going into the motor. If nothing happens, try the other lead to the motor, the headlights should open or close. Once the headlights have opened or closed, the other lead to the motor should now be active to reverse the motor direction. If nothing happens with either lead, the motor has an open circuit because of a bad limit switch or defective windings. Bench testing is not recommended because the limit switches may not stop an unloaded motor in time to keep from breaking the nylon gear or the gear cover, they are both on the weak side.

The light switch has a dedicated terminal to operate the relay. There are two power connections to the stock relay, one from the ignition and the other from the light switch. With the light switch in the on position and the ignition key in the on position the relay is active and power is supplied to the motor to open the headlight doors via the active contacts in the relay. With the light switch in the off position and the ignition on, the relay is inactive and closes on the second set of contacts that direct power to the motor to close the headlight doors. If you are going to use an after market relay, it needs to be the two pole type or the headlight motor will not function properly. The stock relay is a pain in the butt to get at as it is located above the park brake pedal on the A-pillar. I would test the relay before pulling it out.
You can test the relay function with a test light. Turn on the light switch and the ignition switch. Hook the ground terminal of the test light to a good ground and hook the probe to one of the wires of the disconnected two wire harness that would normally go the the headlight motor. One or the other of the two wires should have power. Now turn off the light switch, the other wire should now have power. If this happens, your relay is good. If there is no power to either lead of the harness, your may have a bad light switch or the relay may have failed. The light switch has an internal circuit breaker that sometimes fails. If you have no headlights shining behind your closed headlight doors, the headlight switch is bad. I do not think it would be necessary to rewire the circuit unless you are sure it is faulty.



Dave

Dave, what the OP isn't telling you is that he installed a relay system for his headlights.

Since the OE relay uses ground returning through the headlights to close the headlights, the relay will open, but won't close the headlights in a normal fashion. Basically, ground returns through the bulb filament and that is isolated now because of the new relays.

I've had to address this when I did a headlight relay system for my 300 and went to a simple SPDT Tyco relay to operate the doors.

 

[Waggy]

I went with a relay that powers on wire when the trigger is off and another wire when the trigger is on. It Works!!! The only thing I am wondering if my main power should be coming from a keyed power source or just a constant power source such as the battery?

 

[Davea Lux]

I went with a relay that powers on wire when the trigger is off and another wire when the trigger is on. It Works!!! The only thing I am wondering if my main power should be coming from a keyed power source or just a constant power source such as the battery?

Use a keyed power source, that way if the relay or motor gives out there will not be power to it when the vehicle is unattended. The light switch has an internal circuit breaker, odds are your after market wiring job does not. You probably should install a fuse or circuit breaker in the line from the keyed power source so that you do not smoke the fusable link in the event the motor shorts out.

Dave