‘75 Eldorado convertible top switch tired?

[benji808]

Previous owner rewired the top to a switch under the lower dash. I would like to restore original switch functionality.

When I bench test the original switch, it seems to work fine. The switch receives ~12v power, and when I put the switch in the up or down position, the respective wire has a 12v output. However, once I hook it up to the roof, the voltage to the outgoing wires drops: down still powers the roof, but it's only receiving 9-10 bolts from the switch. Up voltage drops to less than 1 and won't turn the motor at all.

So can these switches get "tired" and just fail under load, or is there likely something else I'm overlooking? I know the wiring to the motor is good because I can "jump" the wires and raise and lower the roof.

Thanks!

[J. Gomez]

Previous owner rewired the top to a switch under the lower dash. I would like to restore original switch functionality.

When I bench test the original switch, it seems to work fine. The switch receives ~12v power, and when I put the switch in the up or down position, the respective wire has a 12v output. However, once I hook it up to the roof, the voltage to the outgoing wires drops: down still powers the roof, but it's only receiving 9-10 bolts from the switch. Up voltage drops to less than 1 and won't turn the motor at all.

So can these switches get "tired" and just fail under load, or is there likely something else I'm overlooking? I know the wiring to the motor is good because I can "jump" the wires and raise and lower the roof.

Thanks!

Benjamin,

Yes those switches do carry all the load for the motor(s) as you mention they will get "tired" with age/usage from the heavy loads.

Not sure if you can open those u and clean them and if you lucky in getting the switch back the best option to save it is to add a couple of relays to drive the motor load instead of the switch. The switch will operate the relay(s) to power the motor.

Good luck...!

[hornetball]

What I would do is retain the switch and then use it to energize a relay to power the motor.  You could mount the relay behind the rear seat right by the motor.  Nobody would ever know.

These days, you NEVER have that many amps going through panel switches.  Relays are always used.

[benji808]

Thank you both! Do you have a picture or a diagram of what that would look like? My electric knowledge is a bit rudimentary...I assume the switch stays the same, but instead of the outgoing wires going to the motor they go to the relay. Does the relay then have a separate power source that the outgoing wires trigger to push into wires going to the motor?

[J. Gomez]

Thank you both! Do you have a picture or a diagram of what that would look like? My electric knowledge is a bit rudimentary...I assume the switch stays the same, but instead of the outgoing wires going to the motor they go to the relay. Does the relay then have a separate power source that the outgoing wires trigger to push into wires going to the motor?

Benjamin,

Here is a simple diagram to wire the relays, the relays are the simple SPDT type (no need to get the ones with a diode aka transient voltage suppression).

You will need to extend the +12V from the switch over to the relay contacts stencil 30 (C1 on the diagram), you will need to run new wires from the switch to each relay stencil 30 (C2 on the diagram) and ground on the contact stencil 85 (C1 on the diagram), the other two wires from the motor up/down will go to the relay stencil 87a (C3 on the diagram).

Good luck..!

[benji808]

Well, considering I started today knowing next to nothing about relays, I'm a bit dumbfounded, but it WORKS!!
I bought two RL44 SPST relays from Autozone (https://www.autozone.com/electrical-and-lighting/relay-and-resistors/p/novita-40-amp-spst-accessory-replay/849394_0_0?searchText=rl44), hooked them up to the same 12v power supply (I used the original powered wire that went to the switch), grounded to the body (I decided to mount under the dash as it felt easier to test and run the wires), then attached the wires from the switch and the outgoing wires to the motor. One thing I wasn't sure about was where to get the new 12v constant for the switch, but I ended up just cutting into an under-dash courtesy light...it seems to be working fine, but let me know if you think I'll light anything on fire 

Anyway, really cool learning experience and I'm ecstatic with the result...crazy how one can resurrect an almost 50-year-old switch with a couple $5 relays. I've attached a couple pictures of in-progress and final product.

Thank you both for the advice and encouragement!

[J. Gomez]

Benjamin,

Well, considering I started today knowing next to nothing about relays, I'm a bit dumbfounded, but it WORKS!!
 

That is what I call "learning while doing the labor work" is the best method.   

One thing I wasn't sure about was where to get the new 12v constant for the switch, but I ended up just cutting into an under-dash courtesy light...it seems to be working fine, but let me know if you think I'll light anything on fire 
 

I would strongly suggest in using the same +12V power feed from the original feed and connect it to the relay contact(s) to power the top motor feeds since it should be protected by a CB (circuit breaker) or a fuse.

If you are using the +12V to just energized the relay(s) from another source that would be fine the relay(s) draw is minimal, so hooking them to the courtesy light should be fine.

Good luck..!

[benji808]

Exactly - original 12v power is powering the motor, the courtesy light is just energizing the relay through the dash switch. Thanks!

[J. Gomez]

Exactly - original 12v power is powering the motor, the courtesy light is just energizing the relay through the dash switch. Thanks!

 

Well now the bad news is you have to wait until the spring/summer to lower the top.   

[benji808]

Well now the bad news is you have to wait until the spring/summer to lower the top.   

Any weather is convertible weather if you're brave/crazy enough