Engine off coasting on my matrix

[Weather Spotter]

My shifter is just like yours, I might have to try it once I get the switch and relay.

[Weather Spotter]

Update:

I went shopping and got the same switches that Niner got
My issue is the those switches are only ratted for 50mA so it will not run a 30A relay. I bought a second relay that is good for 10A @ 120vac/24VDC. The guy at radio shack that it is good for 5A @12vdc. Is this right?

Do I need to have this small relay run the big one? or is 5A good enough for the injector circuit?

[Weather Spotter]

Well I had it all hooked up and tested it. The car cranked and cranked.... I hit the button and it ran, when I let up it shut off. Opps! I hooked my secondary relay up wrong, I had the NC contact hooked to the ground, so I was grounding out the main relay all the time. When I went to fix it I broke a pin off my relay so the project will have to wait until I can get another one.

I will upload some pic later so you can see what I did.

You were right on which wire to snip

[Niner]

Hm, I don't see why that other relay wouldn't work. I would think it should be good for 10A at any voltage below 120 volts. Voltage would cap out due to where you start getting arcing, but current is current - 10A at 24V DC looks the same as 10A at 12DC, or 5DC - because the switch doesn't have a voltage drop across it anyways, unless it's open.

Does your original relay say what the coil resistance is? I found one on Radio Shack that was 30A, and listed 160mA for the coil, but also 400 ohms, so at 15V (the high end in a car) it's still only pulling 37mA. Maybe startup/drop currents because it's not resistive?

Sorry to hear about your relay! I hate when stuff breaks. Did you get one of the ones from Radio Shack with wire pins instead of the flat auto connectors? That's what I used, which is also why I had breadboard - I soldered the relay to a little board, soldered my wires onto that, and then wrapped it in tape.

I came up with an idea for a kill switch that would use this same relay - between the switch and the relay, tap in a second line. Attach this second line into a toggle switch, and from the toggle switch into the normally-open side of a second relay, and then into ground. Power the normally-open relay with the starter signal. During normal driving, this relay won't be powered and the second relay will stay open, so even if you bump the switch you don't kill the engine. However, if you flip the switch off when you leave the car, it's harder to hotwire - the starter signal will also kick the second relay on, which will ground out the first relay, interrupting power to the injectors. Fortunately, theft is not a big issue in backwoods Michigan, so I'll probably never try this.

[Weather Spotter]

I got the same relay you did- with pins rather then spades
I do not have any bread boards to attach it to.

My big relay does not list anything as to specs.

Once I buy another relay I might just use it rather then mess with two relays.
What should I buy at the shack in addition to a relay?

[Niner]

How comfortable are you with soldering?

If very, then I'd get the same little 5A blue relay and a board - the one I got was called a "dual mini board", it was about 3" x 1.5" and could be snapped in two. Each hole has a little copper around it but nothing is connected. You just stick the relay through the holes, solder from the backside, and then it's easy to solder stuff to it from there.

If not, I'd just get the 30A auto relay that they sell. It will probably work with that button.

[Weather Spotter]

Originally Posted by Niner

How comfortable are you with soldering?

If very, then I'd get the same little 5A blue relay and a board - the one I got was called a "dual mini board", it was about 3" x 1.5" and could be snapped in two. Each hole has a little copper around it but nothing is connected. You just stick the relay through the holes, solder from the backside, and then it's easy to solder stuff to it from there.

If not, I'd just get the 30A auto relay that they sell. It will probably work with that button.

I have a 30A auto relay, that was my" big one". I was going to hook that to the button but thecurrent of the relay is like 120mA. The switch can only do 50mA.

I can sodder relitivly well. If the board has rings then I. Should be good. I presum I can get that at the shack? Did you get some screw down terminals as well?

Thanks for all the help!

[Niner]

I did, but that was before I thought of using quick disconnects. My first plan was to keep a butt connector in the car if I needed to patch the lines together. With disconnects, I would just solder stubs (or however long you want to move the relay) of wire direct to the board.

[Weather Spotter]

Update:
Picts of OEM:

glove box removed:


Junction in car:


Shifter nob
front side:


epoxied in place




I went back into town and got the needed supply's.
I got another relay $4.99
A small circuit board $2.99
Some screw down contacts $1.99 for a 4 pack.
Total cost ~$20 (more if you mess up)

It was significantly faster to work with a circuit board then without one.
I soldered the screw contacts to the pins on the relay (with wire):


from the top:


Then I added a termal so that I did not need to splice the ground wires to each other (miss match in size):


Installed and tested:


I put in plugs so that I can put it back to OEM if desired. I can also undo one plug and the car will not start

Thanks Niner for the idea of where to put the switch and how to rig up the wiring It helps me to be able to bounce ideas off people.

[Weather Spotter]

Update:
I took it into town today, it works great. The only issue is that the ScanGauge is still turning off after about 20 sec. If I touch the home button then go to gauge it is still showing my MPG (over 700MPG). I want it to stay on.

How do I fix this?