Need a Fuel Tank Selector Valve

[hatzie]

Originally Posted by wilkin250r

That's pretty close to how I would have done it, but it might be easier to replace the pair of relays with a single DPDT relay.

In any situation, you're running an additional wire to the valve. Whether you change the switch on the dashboard to the style designed specifically for the motorized valve, or you run relays under the dashboard and run power, you're STILL running an additional wire, you can't do it with just the single wire.




On a side note, just because it's an interesting project, I think I've found a way to run the motorized valve with just a single wire, but it would involve a power module (about $20) and a relay, not too much different than a pair of relays.

I was wanted something that was frighteningly easy to service and so common you could get replacements bubble wrapped at WalMart or any big-box auto parts store.

The Micro ISO SPDT relay, in its' many incarnations, has been around for over 4 decades. It's still being used in brand new industrial applications... literally thousands at a time. You can find em in late 1960's VWs and they've used them by the thousands in transit coaches... Open the overhead electrical compartment on a 2004 Nova LFS transit coach. There's literally two 3' x 4' hinged panels of 12v & 24v Mini ISO relays. Even the "modern" automobile, truck, and transit coach designs still use Mini ISO relays in several places where the current load would kill the modern PLC. It's probably going to stay available for a very long time.

I actually thought about using a T-92 DPDT Automotive grade relay but they are simply not as common. They don't have foolproof sockets with mounting tabs either so R&R is more complicated. They are not commonly used in industry so the supply will dry up and blow away. The DPDT relays with mounting sockets that you can find at Radio Snack are simply not robust enough to survive an automotive environment. The footprint of both the T-92 and the clear case relays is larger than the Mini ISO relays with the Lego sockets. At least that was my thinking.......

I'm interested to see what you've come up with using a single wire.
It's fairly entertaining, to me, to see other folks ways to replace obsolete electrical parts without super intrusive and difficult to reverse modifications. I've played that game with Nixie tube driver chips on my Ham-Fest Frequency counter. I eventually found a NOS tube of the correct driver chips and reversed my mod. The gods of electronics and computers Georg Ohm, James Watt, Charles Babbage, and Blaise Pascal were smiling on me when I picked that tube of brand new long obsolete chips out of a bucket and paid $3 for it.
Durn engineers.