Working on 74 model. Checking two other cars I know that when the key is turned to run position the headlamp relay closes. On the car we are working on, the relay does not close, but if we connect 12 volts directly to the coil it will close, so we know it is good. We have checked continuity on both limit switches and both seem to be fine. Looking at the schematic, it looks like the ignition switch supplies power to the relay coil. Can the ignition switch be to blame for head lights not closing?
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maybe just sematics, but the key power is to the relay Contacts and then to the motor

the power to the coil is from the headlight switch
energizing the coil changes the contacts from go down to go up. with the limit switch stopping the motor

could check to see if power is at fuse 10 with key on

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Thanks, anything helps at this point. I have studied the schematic you posted, but I am at odds with it, as it shows there is no voltage on the coil until the headlight switch is turned on, but on a good working system the relay closes immediately with key turned to run position with lights off and down. That's the only way the relay can close is with voltage to the coil, not to the motor or limit switches. That's what we are missing.

If F10 is in the fuse box, all look good, but will check if power is even getting there. There is also a circuit breaker in line with the relay which is not shown, but is okay.
RR, be VERY cautious in connecting ANYTHING to the hot side of an ignition coil. Even low-voltage devices will often function exactly like a rev-limiter. Can't tell you how many 'almost-stock' Panteras with the 'won't rev over 4500 rpms' syndrome I've seen. Usually it's someone that hooked their Holley carb's electric choke to the + side of the coil, or a car alarm.

With the unplated contacts in Lucas-sourced wiring in a DeTomaso Pantera, it's always best to attach extra devices to the + post on a stock alternator, or run a completely separate hot wire off the fuse panel back to the engine compartment, and use that as the source of any needed electrical power back there. Good luck.
“but on a good working system the relay closes immediately with key turned to run position with lights off and down. That's the only way the relay can close is with voltage to the coil, not to the motor or limit switches. That's what we are missing.”


Not sure what you are saying. My reply is based ONLY on my reading of the drawings

The coil de-energized state of the relay’s contacts is the shown position that has the motor logic in the “go down” configuration. with out the coil's magnet, a spring pushes the contacts to the "shelf state"

When the coil is energized, the relay’s contact then change to the motor logic of “go up” configuration. the coil's magnet pull the contacts to the changed state

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quote:
Originally posted by RRS1:
Thanks, anything helps at this point. I have studied the schematic you posted, but I am at odds with it, as it shows there is no voltage on the coil until the headlight switch is turned on, but on a good working system the relay closes immediately with key turned to run position with lights off and down. That's the only way the relay can close is with voltage to the coil, not to the motor or limit switches.
That's what we are missing.

If F10 is in the fuse box, all look good, but will check if power is even getting there. There is also a circuit breaker in line with the relay which is not shown, but is okay.


This is incorrect. The relay coil only is energized when the headlight switch is in the on position as shown in the diagram provided. If lights will not go down when ignition is in the on or acc position I would suspect the limit switches or the fuse that feeds the motor. The next place I would check would be the motor it self.
Here is what I know so far, and I have checked several cars. The diagram is correct for a 72 model....relay located under the passenger foot well. The relay coil is energized, contacts CLOSE by the headlamp switch.

On my 74, the action is reversed. The coil is activated, contacts CLOSE the minute the key is turned on. When the light switch is activated, the relay OPENS, not closes. The headlights work perfectly. Sounds crazy, but true.

Somebody please check their 74 model and see if the relay closes by the ignition switch. You can hear it click.

On the malfunctioning 74 model, the relay will not close no matter what. The motor is good because if the headlamps are hand cranked down, the minute the key is turned on they raise. They raise because the relay is open, not closed as it should be.

I don't believe the limit switches would have anything to do with the relay not closing.
RR,my problems in the past with Pantera headlights not working properly mostly stemmed from someone using the wrong spade-lug on the headlight switch for power. There are a number of powered spade lugs available on the switch but only one will work correctly. The schematic may be correct but it is not as good as a photo in this regard. And it's well known that there are at least four schematics with different published dates, all with small differences.

The other problem is the fact that the headlight-raising motor is designed to run ungrounded but there is only one very short wire provided. There is an excessively tricky composite grommet/isolater with a spade lug that is supposed to isolate the hot power wire, prevent vibrations from cracking the short wire while still connecting to the motor windings. I've found these cracked and either open or partially grounded. I discard the grommet & spade lug and use a common in-line double female connector, well insulated, with a tie-wrap to vibration-proof the short motor wire to a stock power wire.

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