Searching for a wire, hot with engine running...

[JoshT]

99 Ranger 4.0L that has been engine swapped with a 2000 Explorer 5.0L

I stalling a wideband O2 sensor for tuning and need to find a wire/circuit to tap into for powerering it. The instructions include the following.

Do not install the Lambda Sensor in such a manner that the unit is powered before your engine is running. An engine start can move condensation in your exhaust system to the sensor, if the sensor is already heated this can cause thermal shock and cause the ceramic internals inside the sensor to crack and deform.

While the Lambda Sensor is in an active exhaust stream, it must be controlled by Spartan 3. Carbon from an active exhaust can easily build up on an unpowered sensor and foul it.

So I need to locate a wire that is hot in engine run only. This does not need to power the wideband itself, I can use a relay and just have this wire triggering the relay.

Any ideas?

 

[SenorNoob]

What about tapping the Fuel pump wire? It's on for a few seconds when you turn the key on, but then goes off till the engine starts. (Something like over 400RPM I think.)

You could put it on a time delay relay, so it wouldn't start until the engine is actually running. Obviously 10 seconds might not be the amount of time you're looking for. I'm sure there is and adjustable one out there. We use them all time in 24VDC and 120VAC for industrial electronics.

 

[Brain75]

I like your idea, I was thinking (for an accessory myself) of pulling a tap of the alternator directly - have to be after the regulator for those with external regulator and wouldn't be 12v it would be more like 14v, the fuel pump w/ delay sounds like a better place.

 

[JoshT]

Fuel pump is a possibility I'll look into for the future. I am familiar with the time delay relays, but currently batting zero on getting them to work. Bought a time off delay relay to use for something on my F-100. Something that I did not want the power to cut out on while cranking the truck, but don't remember exactly what now. Did not work at all. Haven't given up on using them, just haven't been ready to try again.


For now I found a solution/workaround. This works for my 99 Ranger, I can not speak for how otheryears are wired, so do some checking before you assume that it is the same.

First, the workaround part...

I kind of geeked out on selecting what wideband I was going to use. Opted for a Spartan 3 v2 made by 14point7. One of the reasons for selecting this one is that it offers a bit of user configuration in the controller, stuff that will be benificial for future plans to use it with megasquirt on a different project. One of the offered features is what they call a smart heatup. To quote from the product page:

"Smart Heatup; Temperature Triggered Heating, Spartan 3 will wait for the Oxygen sensor to be heated to 350C by engine exhaust gas before heating up the sensor."

and from the user manual:

"wait, a max of 10 min, for exhaust gas to heat sensor to 350C before heating."

So with that setting enabled it will wait a maximum of 10 minutes for the exhaust gas to reach temperature before turning on the heating element. At the time or temperature mark it will turn on. Meeting either of those should have any condensation cleared out of the pipes. Unfortunately that setting does not come enabled by default, so you have to use a serial command interface (aka special usb adapter and program) to change the setting and endable it. Of course in my geeking out, I bought the kit that included the special usb adapter. Did that today.

Second, the power solution...

Not a permanent installation so I was looking to use an add-a-circuit in the fusebox. Radio was kind of the first place to look. There are two radio circuits, one is always hot for keep alive memory, and the other is supposed to be powered with key in run/accessory. Well for som reason getting power from the keyed radio power did not work. Install the add-a-circuit, turn key on, and no power to wideband. I tried switching to the other circuit incase I had them crossed, but the wideband was powered all the time. Probably somethinmg that I need to investigate further, but the radio seems to be working properly. It wasn't an ideal powersource anyway since it is hot in acessory. I'm not likely to sit with the key in run and engine off for very long, but I might sit with it in acessory for a little while.

Poking around I found that the ABS circuit, fuse #14 in interior panel, is powered in run only. Since my Ranger has all wheel ABS, it has a 10a fuse in this location. A truck with rear wheel ABS would have a 20a fuse. Wiring in this part of the harness is the same between both ABS systems, so not only did I have a hot in run only circuit to tap, the wire feeding it was designed with enough ampacity to easily carry the small load that my wideband would add. Popped the add-a-circuit into that fuse location, and everything seems to be working perfectly.

Between the hot in run only power source and the temperature triggered heating, I should be covered.

 

[Brain75]

Just don't take your sweety to makeout point and sit listening to the radio and looking at stars for any length of time

edit, wait is that hot in "run" only , not accessory too... In my probing I couldn't find any difference in 2nd gen - it was only 2 options, continous or accc.

 

[JoshT]

That's why I opted for the hot in run only circuit. I can sit there with the key in the accessory position all night and it won't power the wideband.

Not that it's an issue. There is no sweety and, at the rate I'm going, there won't be.

Even if there was I'm not sure that there's any place around that could be considered a makeout point, where I wouldn't want to be wearing a bullet proof vest. I imagine that it would be difficult to get in that kind of mood when the wrong type of fireworks are going off, and someone is scoping you out for acar jacking.

 

[901wd#2]

Any chance the oem narrowband O2 sensor has a built-in delay for the heater? Could use that for your signal wire to the relay.

 

[JoshT]

Possibly, that circuit appears to be powered in start and run. To use that I'd have had to tap into the circuit with under the truck or under the hood, which were less than idea for what I was trying to accomplish with this temporary install. The harness with the wideband runs up into the cab around the cup holder, only about 5" tail on each wire once it splits out. To tap into the circuit that powers the O2 sensors I'd have had to run a wire back out to the sensor pigtail or into the battery junction box. I prefer to keep everything simplified and wired inside the cab.

Used a scrap piece of wire from an old project, and ran over to the tap in the fuse panel, and other short scrap over to ground under the dash. Before I get to the point of tuning I'll probably get some conectors and make a little nicer and more modular install. Right now I'm just powering the controler and wideband. It's installed so I won't have to get back under there later and install it. and it's powered so it won't get damaged by sitting in the exhaust stream. I don't even have an AFR gauge connected, I'll get it attached to the SCT tuner soon and make sure I have everything communicating properly.