Here’s the door lock saga! First of all, As a marine mechanic, I have this fetish, I like to be able to prove, by logical troubleshooting, what the problem is! Especially before I change a $120 part! 91 740T

My Central door lock system quit completely! With my meter and test light we have determined the following. The door lock switch and wires are good, but the door switch does not seem to be momentary. Turn it to lock and it makes a continuous circuit, turn it to unlock, it makes a continuous circuit. Is it supposed to do that?

The solenoid functions as it is supposed to! We bench tested it separately and when actuated it sends a pulse to the actuators (had to send off and get the Haynes British 740 manual to figure out the circuits.) The solenoid is the long box with two relays and a timer circuit on each leg. It reverses polarity to the door motors when actuated.

(Note when this relay is plugged into the board it actuates. I found that rather strange but we reasoned that the circuit is hot all the time and the door switch is making either lock and unlock grounds all the time, but the output of the relay is momentary, so who cares?)
Or is this a problem?

Finally we decided to remove the trunk actuator and test it. It would not actuate at first, seemed to have a dead spot. Took the actuator apart (Rectangular box, linear actuator with a Rockwell permanent magnet motor inside.) Gently pried the motor apart and tried cleaning the commutator with toilet bowel cleaner, runs much better, but still quits. Nudge the gear slightly and it turns (There does not appear to be a thermal switch in this motor, like the 200’s) At the same time we tried actuating the other actuators using the trunk circuit to see it there was a problem from the relay wiring to the motors. Nothing actuated!

Right now this could lead one to believe that we have 4 bad door lock actuators. I really have trouble believing that all 4 actuators are bad. In any event, what's the going price for junkyard actuators and what are some good sources?

My next step will be to go in the doors and check each motor and circuit.

I’d appreciate your thoughts on this deal!

Regards

Woody

91, 740T