Octane switch plan

Topic: Octane switch plan (Read 1708 times) previous topic - next topic

Octane switch plan

April 07, 2012, 02:21:42 PM

I think I found a way to use the fuel selector switch, without having to use the original ford switch.
Everything is named generic, because I do not have diagram with me to remember the wire colors :lol:
Will use the SPDT relay, normally closed for Regular fuel, and switch relay on for premium fuel.
I think I should be able to get away with this idea.

Octane switch plan

Reply #1 – April 08, 2012, 12:55:47 AM

Having a sport, I'm not really familiar with this switch. Is there any reason why you cant just use a two way toggle switch instead of a relay?

Octane switch plan

Reply #2 – April 08, 2012, 01:21:35 AM

The octane switch on the TC's are on, or on. no real off position. There are 3 wires. Always 2 of the 3 are in a completed circuit. Digikey has a switch that would probably do it, but I already have these parts, and I want the 2 switches to match :D
I've already redone the PRC switch, finally the old one was so messed up, if you switched to firm, it'd lose connection within a few seconds.

Octane switch plan

Reply #3 – April 08, 2012, 07:01:10 AM

You are over engineering this thing. No relay is required at all. Just a simple single pole switch with on illumination feature if desired. All the octane selector relay does is supply SIG-RTN to octane selector pin 24 . With the switch closed you are in HI TEST WITH IT OPEN and SIG RTN removed from pin 24 you are in regular. Dont over design this. It is a simple on off switch. Good luck Tom

The octane switch on the TC's are on, or on. no real off position.

^ ??????????????????????????? I dont get this one BIT. Of course their is an off position. The switch has to open pin 24&46 of the ECM to drop it out of premium. I can draw you a simple print if you like. But this circuit is as simple as it comes!!

Octane switch plan

Reply #4 – April 08, 2012, 01:28:49 PM

I agree with Tom, a relay seems like overkill.
However, according to the 88 EVTM, you already have a relay.

Octane switch plan

Reply #5 – April 08, 2012, 02:24:43 PM

Look at that circuit from ford. Is that the dumbest thing you have ever seen designed in your life. A relay controlled by a switch to bridge 2 ECM pins. What a waste of time money and relays. What was Ford thinking when they designed this. Someone had a lot of stock in BOSCH when they designed this BOONDOGGLE!!!

Octane switch plan

Reply #6 – April 08, 2012, 02:49:16 PM

Quote from: TOM Renzo;386300

Look at that circuit from ford. Is that the dumbest thing you have ever seen designed in your life. A relay controlled by a switch to bridge 2 ECM pins. What a waste of time money and relays. What was Ford thinking when they designed this. Someone had a lot of stock in BOSCH when they designed this BOONDOGGLE!!!

Yeah that, and I am still pondering why they needed ground on both sides of the relay coil when the switch is off.

Octane switch plan

Reply #7 – April 08, 2012, 03:43:59 PM

They don't. That ground terminal on the switch is only there for switch illumination. The bulb inside the switch is connected between the ground and the yellow wire to the relay. When the switch is off the bulb is grounded on one side and gets no power from the relay side. When the switch is on the bulb gets its power through the relay side (which now has power thanks to the switch contacts) and its ground comes from that ground you see. The ground to the relay when the switch is off has no other function and does not affect relay operation at all, it's just that way to allow an illuminated switch with only three wires and one set of contacts inside the switch (to configure it any other way would require a second set of contacts and at least one more wire). Most switches that light up when turned on are wired this way, including aftermarket ones.

Hell, it's easier to draw than to explain, so here's a drawing detailing the innards of this type of switch:

Octane switch plan

Reply #8 – April 08, 2012, 04:51:36 PM

I follow. I didn't realize all that extra circuit was for was just a light

I just assumed that other circuit in regular mode was for a more important reason.

Glad to see this info, Less work to hook the switch up

Octane switch plan

Reply #9 – April 08, 2012, 05:11:26 PM

Actually, now that I think of it, all that extra wiring IS just for the light. Without that factory relay in the circuit that red/yellow wire (pin 24 on the ECM) would be grounded when the switch is off. The ECM probably wouldn't like that one bit, hence the relay. If you wish to use a lighted switch the relay is a neccesity...

Octane switch plan

Reply #10 – April 08, 2012, 09:27:05 PM

Thunder, thanks for the explanation.

Octane switch plan

Reply #11 – April 09, 2012, 06:04:58 AM

I totally forgot the indicator lamp Thunder D'OH!!!

The lamp is shorted out in premium mode. In reg mode it gets it's ground through G 902 illuminating the switch handle. Another words in regular mode warning by illuminating the handle. Thunder that is exactly why the relay is their Thanks for clearing that up. Thanks.

Note i am surprised the print did not show that. I even looked it up in all data. No lamp. Good call explaining it THUNDER. When i transplant the 2.3 in to mustangs i just jump pins 46&24 Permanently and eliminate the octane selector. Much easier

Here is an easy way to do it with a 4 pr0ng illuminated switch.

Here is what the print should have looked like

Octane switch plan

Reply #12 – April 15, 2012, 12:38:41 AM

Used the regular light up switch from autozone, works perfectly :D

Now I just have to secure the switches as they are slightly smaller, and reattach the sticker

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