1959 Power Seat Fixes

[YellowRose]

Posted by and for Shandon Steve

I'm not sure how to send this to the proper area but wanted to share something I encountered during our restoration of the '59 convertible we have been working on.

The power seat would only raise and lower but wouldn't move forward or back. I found the relay controlling that motion was defective and started looking for a replacement. None of the normal suppliers had that relay but I was able to locate one on eBay NOS but he wanted $135.00. Being a life long electrician there had to be a better solution. Studying the wiring diagram in a 1960 shop manual that came with the car I discovered a much less expensive option. I've included a pic of the page from the manual and will attempt to explain. All anyone needs is a 12 volt DC single pole relay with a 30 amp rating(available at any auto parts supplier) to replace the factory unit. If you look at the wiring diagram, page 15-6 in the 1960 manual there are 2 boxes labeled "HORIZONTAL MOTOR AND RELAY" and "VERTICAL MOTOR AND RELAY. In the box you will see at the top FIELD (fore and aft) or (UP&DOWN) plus and BAT & ARMATURE. The word FIELD is actually the coil of the relay, and between BAT and ARMATURE is the contact of the relay. If you match the wiring to these areas in the new relay the seat will function just fine. The reason this works is as follows.

1) pushing the seat switch in the "forward" position energies the yellow-green band wire and the red wire going to the motor. The coil energies because current flows through the coil, into the yellow wire going to the motor which has a heavier winding than the coil winding and then to ground to complete the circuit. There's enough current flow to energize the relay but not enough for the motor winding for AFT direction. When the relay energizes the contacts close supplying current to the armature and the motor runs FORWARD. Moving the seat switch in the aft direction feeds the green-yellow band wire and the yellow wire to the motor, and the circuit operates in reverse. I know this is somewhat confusing but the new relay is less than $10.00.

[simplyconnected]

Ray, I cannot read the picture because it is so small. Can you fix it?

[YellowRose]

Apparently not, I tried. Perhaps Shandon Steve will repost it...

[jopizz]

Try it now. Steve sent me the same photo.

John

[YellowRose]

Thanks John! Apparently, when I went to move it out of the other thread I got the thumbnail and not the full graphic. Now it can be read!

[simplyconnected]

image.png
Here is the diagram from the Ford Service Manual.
These DC shunt motors have separate field windings for Forward and Reverse.(or up and down). This is very different from permanent magnet motors.

Right now, I'm extremely busy with Thanksgiving coming Thursday and two speakers to replace speakers in (going from 10" to 12" in both).
Later, I will draw a circuit using modern relays. - Dave

[simplyconnected]

As promised, here is the wiring diagram to retrofit modern relays (to replace expensive OEM relays):

image.png

Notice that there are TWO power leads. Also, there are two circuit breakers. It's very important that these circuits NOT be integrated with each other. That is why we use relays, so heavy current to move the seat comes from the relay contacts, not the seat switch. The circuit breakers are there to protect the wires. Connecting the two circuits together will melt the wires before the breakers trip.

I labeled the relay coils with + and - because some brands of these relays come with an internal 'flyback diode'. If the coil is connected in reverse, the diode will short circuit. Of course, some brands have no diode across the coil, so better to be safe than sorry.

I like the idea of using modern relays because they are so inexpensive and readily available. They live under the power seat, out of sight. If you have questions or want me to describe how this works, let me know. - Dave

[simplyconnected]

Ford Electric Motors & Generators
For the 'techies'. By contrast, today's motors use permanent magnets instead of field winding. Back then, NONE of the motors and gen's used magnets, they made their own magnetism with field windings. (Many home radio's large loudspeaker also used powered field windings instead of magnets.)

Notice that Power Seat and Window motors are 'shunt' motors meaning, their field windings are paralleled with the armature. They had four wires coming out:
Two for the armature brushes, two for the forward field and two for the reverse field.

Yes, that's six wires but hidden inside the motor, the armature and both field wires are connected together to make one ground lead. Why two fields? Because they are both wound backwards from each other, which produces magnetism in either direction. Simply choose one for clockwise and the other for anti-clockwise rotation along with the armature.

To reverse any DC motor either the armature leads must be reversed or the field windings. If you simply reverse the car's battery leads, the motor will NOT reverse direction. Even though you reversed the armature polarity, you also reversed the field polarity (which is the same as not reversing them at all.) In Ford's case, they simply added another field winding but wrapped it in the opposite direction of the other field winding.

These 'rules' also apply to starter motors. Boat starters (with counter-rotation engines) had their field windings reversed, not the armature. Ford only started using permanent magnet motors because they are smaller size for the same HP output.

Think about this... back in the day, there was NO solid state. The entire technology revolved around coils, relays, resistors and motors, controlled by vacuum tubes (if necessary). Car voltage regulators had the 'cutout relay' with coil windings in BOTH directions and they worked with either positive or negative ground. Yep, mechanical regulators had no diodes so they worked with either polarity equally as well. - Dave