Installing Relays on 1967 Barracuda Convertible Top

[mopardude62]

I have owned my 1967 Barracuda Formula S convertible for almost 40 years. I bought it from the original owner in 1987. After repairing the convertible top switch twice, and replacement switches being somewhat hard to come by, I decided to put my convertible top on relays. I wanted an improvement that was 100% reversible. The pictures aren’t the best, it’s tough get up behind the dash, take pics and be able to show things clearly, but hopefully you get the idea.

I removed the seat to make sure I could reach up behind the dash and have plenty of mobility to work. I removed the left kick panel, pulled out the insulation card and found a place to mount my relay board. There was even an existing hole, so I just found a self-tapping screw and used that to mount my relay board.

I made a template out of cardboard, transferred the pattern to a scrap of ¼” plastic I had laying around. I laid out my relay sockets and 30amp circuit breaker on the board, marked and drilled the holes.

I mounted my relay sockets and circuit breaker to the board and drilled a hole in the middle for mounting with my self-tapping screw. Following the colors already in the car (yellow is top down, brown is top up) I soldered the pigtails onto the terminals and inserted them into the bottom of the relay sockets.

I left the wires long enough to do a test mount and determine how long each wire should be. I temporally mounted the relay board under the dash in the final location. I determined how long each wire needed to be before trimming the wires and soldering on the appropriate connectors to keep this installation completely plug and play.

With the board complete and mounted, I needed to find a place in the fusebox for 12V (key off) hot as my trigger connection. (This is where the pics get a little difficult) I connected to the fuse box piggybacked onto the cigar lighter, ran that (red) wire out to the top switch, plugged in my trigger wires to the switch and the high amperage feed wires to the wiring harness which leads to the back of the car and the top motor.

In the last picture you can see the two heavy wires (brown and yellow) at the top left plugged into the harness connector that leads to the top motor behind the back seat. You can also see the trigger wires at the bottom of the picture (same colors brown and yellow) that lead over to the appropriate terminals in the convertible top switch. The big red wire in the middle is the original power feed wire coming from the ammeter stud which I used to feed power to my circuit breaker. The relays work perfectly and I will not have to be concerned with the convertible top motor current running through a switch that is becoming increasingly difficult to replace.

 

[jeff alder]

That's nice work and a great idea Mopardude. Let the relay contacts carry the load and just energize the low load relay coil with the top switch! TADA...Mopar should have done it this way to begin with.

 

[mvh]

I bought a kit from crackedback who sells the headlight relay kits. His kit puts the relays near the pump, accessible from the trunk. This was easy for me to install because I was replacing the carpet, so the seats were out of the way.

 

[67Dart273]

So you are still using the harness wires that ran from the switches to the motors? How large is that wire? Maybe you should have considered (reversible) disconnecting the original harness wires and running larger motor wires from the relays to the motors. Relays are not just to save switches. In a "clean" design, you would mount the relays at the load, or close to it, so the undersized switching wires, as well as the switch, are relieved. But it's also the MOTORS. It generally is not good for motors to be run at too low voltages. If nothing else, that increases the damage to brushes and commutators

 

[crackedback]

I bought a kit from crackedback who sells the headlight relay kits. His kit puts the relays near the pump, accessible from the trunk. This was easy for me to install because I was replacing the carpet, so the seats were out of the way.

Yes I do and thanks for the mention. Good idea. Mine uses stand alone wiring to carry load up to the connector at the vert pump. Unfortunately with the OEM charge path, there is no perfect spot on our mopars to grab power in both engine on and off situations, always a compromise.

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Relay Kit for convertible top cars. They work on the same basis as a headlight relay kit, removing the load from the stock wiring, relay and switch. Those up/down switches for a vert top car aren't cheap! NO CUTTING REQUIRED! I use a shrink tubed 12 ga wire with a 30 amp fuseholder or fusible...

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Cool deal that the OP did the work on his own.

 

[jeff alder]

So you are still using the harness wires that ran from the switches to the motors? How large is that wire? Maybe you should have considered (reversible) disconnecting the original harness wires and running larger motor wires from the relays to the motors. Relays are not just to save switches. In a "clean" design, you would mount the relays at the load, or close to it, so the undersized switching wires, as well as the switch, are relieved. But it's also the MOTORS. It generally is not good for motors to be run at too low voltages. If nothing else, that increases the damage to brushes and commutators

That should not be a problem in this short DC circuit. The load wires were already appropriately sized as shown in the picture. He also would have had to run his trigger wire and the control power wiring throughout the car rather than just doing it under the dash. I like his design change. It's close to the original power source and circuit protected.

 

[413]

But it's also the MOTORS. It generally is not good for motors to be run at too low voltages. If nothing else, that increases the damage to brushes and commutators

When voltage goes down the amperage goes up to perform the work. This is OHMS law.

So when you operate the top motor you should have the engine running @ 1200 RPM so the charging system is up to full voltage, 14.5 or so. This is much easier on the electrical system than with engine off and battery voltage dropping the whole time the top motor is running. Same with power windows.

Every motor switch and connector will than you.

 

[mopardude62]

The original wires that run from the switch to the motor are 12 gauge. I used 12 gauge wires for my load wires the trigger wires are 16 gauge.

In order to mount the relays at the load (in the back near the motor) I would have had to run a 12v battery wire from the battery to behind the rear seat. Also the two trigger wires would have had to run from the switch to the back near the relays.

I figured it was six of one half dozen of the other whether or not to mount the relays up front or near the motor.

It works well the way I configured it.

 

[jeff alder]

you might want to check your math on that. Ohms law states voltage and current are proportional as long as the resistance remains the same...thus voltage up current goes up...voltage down current goes down.

 

[jeff alder]

according to ohms law what happens if the voltage goes down - Bing

 

[67Dart273]

The original wires that run from the switch to the motor are 12 gauge. I used 12 gauge wires for my load wires the trigger wires are 16 gauge.

In order to mount the relays at the load (in the back near the motor) I would have had to run a 12v battery wire from the battery to behind the rear seat. Also the two trigger wires would have had to run from the switch to the back near the relays.

I figured it was six of one half dozen of the other whether or not to mount the relays up front or near the motor.

It works well the way I configured it.

Yeh. I was speaking more that the wires might be undersized. In that case you are good. It's amazing that "back then" things were so badly done, for some circuits , and nowadays, auto electrics are almost OVERdone!! LOL

 

[67Dart273]

The original wires that run from the switch to the motor are 12 gauge. I used 12 gauge wires for my load wires the trigger wires are 16 gauge.

In order to mount the relays at the load (in the back near the motor) I would have had to run a 12v battery wire from the battery to behind the rear seat. Also the two trigger wires would have had to run from the switch to the back near the relays.

I figured it was six of one half dozen of the other whether or not to mount the relays up front or near the motor.

It works well the way I configured it.

I was thinking the motor wires were undersized. No, the only new wire you would have had to run, for a rear mount relay setup, was the new larger 12V supply. You would have used the existing wires right from the switches to trigger the relays.

 

[mopardude62]

You’re right Del, I could have used the existing “motor” wires as the trigger wires!!

 

[Dana67Dart]

You’re right Del, I could have used the existing “motor” wires as the trigger wires

I was going to point that out, but dell beat me to it. I also was trying not to be a Dana downer!

I applaud your creativity,

The alternate method no wiring changes happen under the dash and only a new power wire gets run from the terminal on the OEM switch after the circuit breaker to the pump area to power the relays. The original wires simply trigger the up or down relay.