Help!
Thread Starter
6th Gear
Joined: Jul 2007
Posts: 6
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Help!
We have a 74 and the power windows quit working on both sides. The motors are brand new so I know it's not the motors. I have put a new power window relay in (under the console) and I know I get power to the relay. I am not getting power to the switches. What do I do?
Instructor
Joined: May 2007
Posts: 112
Likes: 1
From: Chadds Ford PA
I don't have a schematic for a 74, but could have sworn that there were high current switches with a metal body circuit breaker and no relay. How many wires are coming off of what you're calling a relay?
Instructor
Joined: May 2007
Posts: 112
Likes: 1
From: Chadds Ford PA
That's not a window motor control relay, that's the relay that simply sends power to your high current window switches when the key is turned on. (later years use a low current switch with a more complex relay to control the window motors).
Basically, it works like this. The power for the window motors comes from the horn relay under the hood. It is constant (always on). It then goes to a two terminal circuit breaker. An orange wire comes off of the breaker and goes to the relay you found. The purpose of that relay is to connect the high current line from the breaker to the window switches when the key is turned on.
The black wire on the relay is the negative side of the relay's coil, it goes to ground. The pink/black wire comes from the ignition switch. That should show +12vdc with the key in the run position (that line is fused, make sure your fuse is good). That low current 12 volts from the ignition switch closes the coil inside the relay and connects the high current orange wire to the red wire in the relay plug. Doing so supplies high current power to each window switch when the key is on. The window switch is a simple three position switch that supplies +12 vdc to one wire for up and one for down. Ground for the motor is obtained from the door. With the key on, you should have +12vdc on one terminal of each switch. With the switch pressed, you will have power on two terminals and the window should be moving.
You should get your meter and figure out where the disruption in the circuit is. Let me know what you find.
Basically, it works like this. The power for the window motors comes from the horn relay under the hood. It is constant (always on). It then goes to a two terminal circuit breaker. An orange wire comes off of the breaker and goes to the relay you found. The purpose of that relay is to connect the high current line from the breaker to the window switches when the key is turned on.
The black wire on the relay is the negative side of the relay's coil, it goes to ground. The pink/black wire comes from the ignition switch. That should show +12vdc with the key in the run position (that line is fused, make sure your fuse is good). That low current 12 volts from the ignition switch closes the coil inside the relay and connects the high current orange wire to the red wire in the relay plug. Doing so supplies high current power to each window switch when the key is on. The window switch is a simple three position switch that supplies +12 vdc to one wire for up and one for down. Ground for the motor is obtained from the door. With the key on, you should have +12vdc on one terminal of each switch. With the switch pressed, you will have power on two terminals and the window should be moving.
You should get your meter and figure out where the disruption in the circuit is. Let me know what you find.
