6V Classic Car: relays for subsystem control

Thread Starter

shortmort37

Joined Jul 20, 2016
18
I'm interested in setting up a 6V relay block for enabling power to headlights, heater blower, vent blower, wipers, etc. for a classic car with a 6 volt positive ground system. I also have a Borg-Warner Overdrive with a switch that operates a N/O and N/C pair - it would be nice to power both with a single relay, if such a unit exists; but separate relays, if not. Can anyone recommend a vendor for parts - both a firewall block into which to plug the 6V relays, and the relays themselves?

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Dan
 

drc_567

Joined Dec 29, 2008
1,156
If you are in the US, you might inquire at a camper or recreational vehicle supply store. These stores seem to have some experience with applications of this nature.
 
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Thread Starter

shortmort37

Joined Jul 20, 2016
18
I found these: https://www.cruisingelectronics.com/6-volt-relay

They look like the bosh relays,but in 6V. www.part-express.com has connectors,

That company in the fisrt link has a 6-12 V converter. https://www.cruisingelectronics.com/6-to-12-volt-converter I don;t know if that's an option (Make most of the relays 12V) for stuff that works in ACC, if there is such a thing.

I've run into this https://www.delcity.net/store/Dill-Blox-Modular-Power-Distribution-Systems/p_820371 company before.
The Dill Blox are amaaaaazing! I watched the vid, it seems simple enough. Thanks so much for the lead! -Dan
 

Thread Starter

shortmort37

Joined Jul 20, 2016
18
Doesn't the overdrive use a big Ford style starter relay? I have my doubts that a Bosch cube style relay would handle the solenoid on the overdrive, especially at 6V.
The purpose of the N/O and N/C relay pair, would be to simulate the kickdown switch - not to replace the overdrive relay.

On MoPars, the kickdown switch mounted on a carburetor bracket deactivates the solenoid (N/C goes to open), at the same time it momentarily shorts the ignition (N/O goes to closed). With the loss of torque applied to the solenoid, the pawl is free to release. However, the replacement kickdown switch I bought is bulky, and requires a lot of pressure to activate. I'm going to place a micro-switch somewhere in the fuel linkage to simultaneously activate two relays on kickdown - on N/O, the other N/C - to effect the change.
 

shortbus

Joined Sep 30, 2009
8,873
On MoPars, the kickdown switch mounted on a carburetor bracket deactivates the solenoid (N/C goes to open), at the same time it momentarily shorts the ignition (N/O goes to closed).
That's how Ford and GM did it too. You just need to find a microswitch with a high enough DC amp rating.
 

shortbus

Joined Sep 30, 2009
8,873
But that is why the originals were so big to handle the relays. 6V takes more size wise than 12V, that's why 12V battery cables are smaller, higher current through a smaller lighter wire.
 

Thread Starter

shortmort37

Joined Jul 20, 2016
18
But that is why the originals were so big to handle the relays. 6V takes more size wise than 12V, that's why 12V battery cables are smaller, higher current through a smaller lighter wire.
You mean to say, because P = V x I, if you halve the voltage you have to deliver twice the current in order to provide the equivalent amount of power.

No question. But you are confusing circuits.

The original equipment overdrive relay is activated by the lockout switch, N/O but closed by pulling out the overdrive handle. That in turn supplies current to the solenoid, which mechanically engages overdrive. The current to the solenoid through the overdrive relay requires 10 gauge wire.

I am not replacing this relay. I am keeping it.

The circuit that activates the overdrive relay, also has the kickdown switch in series. I am replacing the *kickdown* switch - with a N/O and N/C contact pair - with two 6V relays instead.

See attached diagram. My goal is to replace a switch that requires substantial mechanical pressure to activate, with a light-activation micro-switch that enables two relays to effect the same change. I don't know how else to explain this.

overdrive.jpg
 
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Thread Starter

shortmort37

Joined Jul 20, 2016
18
... that's why 12V battery cables are smaller, higher current through a smaller lighter wire.
Oh, and just to say - you've got this backwards. 12V automotive systems require *less* current to deliver the equivalent amount of power (P = V x I again), that's why with a 12 volt system you can deliver roughly the same power with less current - and hence, smaller wire. The bigger the wire, the greater the current carrying capacity. Reduced wiring costs were an impetus for car manufacturers to go to 12V systems.
 
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