Power accessories became popular on cars in post-war America. Although a few manufacturers used them in the early '40s, they really didn't become industry-wide until after WWII. The first systems were Hydro-electric, and this system continued on most cars from 1946 through 1953. In 1954, with many manufacturers changing to 12-volt electrical systems, they went to all-electric systems on windows and seats, retaining the Hydro-electric systems on convertible top mechanisms. GM changed to all electric windows in 1954 on the following cars: Buicks, except for 66C and 100 Series cars; Cadillacs; Chevrolets (front windows only); Olds and Pontiacs (front windows only).
We thought it would be of interest to cover the "all electric" system in contrast to the Hydro-electric system in last month's Driving Old Cars article. (See www.southernwheels.com and follow the "Archives" link to the November '05 article.) Our subject car for this article is our 1954 Cadillac Coupe deVille. We had just waxed it and were going to take a ride up Lookout Mountain, when I got into the car, pressed the power window switch, and the driver's window went up and stayed there. We cancelled the ride and spent the day learning about how the Cadillac power windows work. While we are covering GM's all-electric systems in this article, most cars of this vintage are similar. Each window functions independently of the other windows. The components of each window are: Circuit breaker, relay, electric motor and switch. A single-pole, double-throw switch activates its relay, then the relay switches the motor circuit. The relay directs current to the armature and field coil of the motor. The current direction in the field coil is determined by the switch position, making the window go up or down.
PROBLEMS: The problems in the Hydro-electric and the all-electric systems are similar. One common one is window or linkage bind, indicated by slow or no movement when the up/down switch is activated. This is what happened on our Cadillac. The window came up too far and got into a bind in the channels, and when we activated the switch, the window wouldn't move up or down. There was no sound at the motor, leading us to believe that the motor was bad. We had to remove the door panel to find the problem. The window had pulled loose from the glass setting tape in the door glass track. Although the window was in the "up" position, it was in a bind in the side window channels and wouldn't go up or down. There can be other reasons for this problem as well: Low battery, improper wiring, bad switch or relay, blown circuit breaker or faulty motor. Other window failures include one window that will not operate from the master switch, but will operate from its individual switch. If this should happen, check for a broken wire between the relay and the master switch, or a bad master switch. If the window operates in the wrong direction when the switch is activated, the wires to the switch, motor or relay are probably connected backwards.
TESTING: To check for current at the door window switch, connect a test light to the center terminal of the switch terminal block, then ground the test light to the car body. If the test light doesn't light, there is no current at the terminal block. To check the door window switch, place a jumper wire on the switch terminal block between the center terminal and one of the motor wire terminals. If the motor works, the switch is defective. To test the wire between the switch and the motor, place a jumper wire on the center terminal of the switch and the terminal of the motor wire to be checked. Disconnect the end of the motor wire "A" from the motor lead and connect wire "A" to the test light, then ground the test light to the car body. If the tester does not light, there is no current at the wire "A" terminal contacting the tester. To check the door window motor, first check the motor to be sure it is grounded, by way of its mounting screws to the inner door panel, then connect a jumper wire to the positive post of the battery and the other end to the lowering cycle motor lead wire terminal. If the motor does not operate, the motor unit is defective, or the window assembly is in a bind. To check the raising cycle of the motor, repeat the above by running the battery lead to the raising lead of the motor.
REPAIRS: In our case of window bind, we had to remove the window and re-set it in its door glass channel. To remove the door glass, first the door panel was taken off by removing the spring clips holding on the vent window and door handles (making a note on the position of the handles before removal). We removed the screws to the heater duct and all screws holding on the door panel, then removed the upper section of door glass channel (or door panel cap), then removed the upper and lower door panels. We lowered the door glass to a position where we could reach the window track screws to free the window for removal, then disconnected the battery. Next, remove the access panel covers from the inner door panel and removed four screws holding the window assembly to the regulator cam that allows the window to move up and down, then disengaged the window assembly from the regulator cam, pushed the glass up to the almost-closed position, then tilted it in and pulled it up and out of the door. With our window out, we checked our window channels, put white grease on the lift arm linkages and removed glass from the glass channel and installed some new glass setting tape. Then, using a rubber hammer, carefully tapped the glass down into the new setting tape, securing it into the window assembly regulator cam channel. The window was then re-inserted, reversing the previous procedure. We had tested our motor and switches, so no further work was needed, except to adjust the stops that keep the window from rising too far in its "up" position. If the regulator is removed, the regulator lift arm must be in the "down" position to install the regulator.
Our Cadillac power windows now all work correctly, and we have the satisfaction of having gone through our system, enabling us to know that everything is in good working order. This is a repair that just takes patience, a little time, and minimal tools: a door spring clip remover, screw drivers and a test light. Part of the fun of working on old cars, is doing it yourself! (Note from wife: We are still waiting to take that ride up Lookout Mountain!)
All the best to you and your families this Thanksgiving. Enjoy your cars! Keep 'em driving!