1976 Eldorado Conv top will not go up

[Mathemagician44]

Hi all.  Last month I purchased this good-condition Eldorado on a whim.  All worked then, but over a month or so, reliability of the top was intermittent.  It went from all good, to having to repeatedly push the up button until it worked.  Initially a few times and then many times.  Now it doesn’t seem to work at all. I put on a new relay and no change.  I can swap the yellow and green wires to at the relay-to-motor and force the top to go up when I push the switch down - no movement/sound when I push up.  In this scenario, the top acts/sound as it should and functions smoothly.  Likewise, When yellow/green are correctly connected to relay, the top goes down as it should and I get no movement/sound from pushing the switch up.

More details:
The switch puts 12.7 volts to the gray/purple wires leading into the relay when I push up/down.  So I assume this means the switch is good.

What seems odd to me is that using the red wire as a constant and then testing the yellow/green wires from relay-to-motor, I get 12.7 volts to both yellow and green whether I am pushing up or down. 
Shouldn’t voltage or come to the yellow when I push the switch in one direction and green when I push it in the other direction?  If both wires get voltage with either direction, what does that mean.

If it matters, the voltages listed above were taken from the relay tabs with the wires to the motor detached.

[TJ Hopland]

The circuit is more complex than you would expect.   Switch activates the relay which then goes to the brushes and armature.  The switch directly feeds the field windings which gives the direction.   Which ever direction of the field winding that isn't being used provides the ground to the relay coil. 

[Mathemagician44]

I figured it out.  I took the switch out and noticed that the rocking arm had unequal gaps at the contacts.  I stuck a piece of paper between contacts on each side and pushed the switch each direction.  I noticed that in the up direction, the paper had resistance to being pulled out, but not as much as the other side.  I took the switch apart to bend that arm down a little so the contacts made firmer connection.  Once I got it back together, it all worked, many times. 

So maybe the contacts touched enough to send a voltage, but not when under load?  I don’t know if that makes sense, seems like it doesn’t.  However, she is working now.

Of note, you will read to disconnect the battery web working on the top.  Do that.  The switch is open on the sides, and it is very close to a metal support for the dash.  It’s hard to to accidentally glance against that frame when you are putting the switch back.  Via accidentally touching that switch to the frame, it sparked and seems to have burnt up my new relay.  Good thing that my old one still worked. 

I wanted to take the radio out while I was in there to see why it isn’t working, or to test wire a known working speaker.  But I didn’t see quite how to get it out so I put it back together and will probably have a question about that in the future.

[The Tassie Devil(le)]

G'day Matt,

Congratulations on working it out, and thankfully, you didn't cause more damage when arcing the wiring.

What you experienced is typical of something that hasn't been used for a long time, and suddenly put back into service.

This happens a lot with vehicles that have been stored for years, then sold, and the new owner starts to use it like never before.   Not just electrics, but other parts where lubrication and lubricants have hardened and dried out.   Like Speedos, Window runners and slides.

Lubricated parts require movement, and the worst thing is lack of movement.   

Bruce.

[James Landi]

Had the identical problem with my "rocker switch" on my 72.  Oxidized contacts -- and using a digital multimeter threw me off... sure, it reads the appropriate voltage, but without the necessary amperage, it's a no go on the top circuitry.   Now, I've learned to "second guess" the gauge.   James

[76 cadillac bob]

Greetings All
I have not been on the forum for a while, luckily things running smooth with my 76 eldo convertible. Reading about the top,  Bruce you make a very good point, I found the bolts near the rear window of mine were coming loose. There was  lock tite at one time but it was old and the nut holder was missing so it could just turn. The passenger side almost came loose from the main frame bracket, it would have been a major disaster and probably caused breaks in the mechanism. Please check all bolts as the scissor mechanism is very heavy and complicated. My top person totally fixed mine. Keep fitting greased and do put the top up and down regularly to keep everything moving.  I discovered the loose bolt by noticing the left and right sides were not coordinating when I was putting the top up..... Lopsided.
Just a handy hit to keep our cars in good shape..also run wipers/washers windows and AC regularly.
Glad you fixed everything
I love mine you will as well.
Cadillac Bob