Project Van: More Electrical Tricks

We’re working on turning this $2000 van into a do-it-all machine that can tow a car to the track, then serve as a mobile workshop and hotel room for the weekend.

Another day, another project. 

The pin on the van's 7-way connector that charges the trailer battery has never worked. We know exactly why, too, because we were there when the current trailer wiring was installed a few years ago: We couldn't find a convenient place to connect the wire. We also knew the van was probably getting traded in soon. Hah! Joke's on future us, past us!

Anyway, we sat down with the Ford body builder's handbook, which is never more than a quick Google away, and has info on all sorts of neat electrical tricks built into this van's control modules, like stationary elevated idle control to run a power take off. I found something particularly interesting: shove any standard 40A relay into the spare spot in the fuse box (closest to the top of the photo), and the red wire in the bundle that ends on the driver's side of the firewall will magically be powered only when the van's ignition is on and the battery voltage is still high enough to start the vehicle. Plus, it's already fused, too. This is called the trailer battery charge control relay, and after putting one in and hooking up that red wire, we now have a trailer charging circuit that can never run the battery dead. 

With our trailer wiring fixed, we moved on to another issue we'd been putting off: We really, really needed a transmission temp gauge. At 223,000 miles, the van is still on its original automatic transmission. GRM serviced it every 70,000 miles, and we just had the fluid and filter changed again, but sooner or later it will die. 

When towing with an automatic, priority number one is keeping temperatures under control. We towed to the rallycross with overdrive off, but honestly we have no idea what's happening inside the slushbox.

Enter the Scangauge II. We picked it up used on eBay for $89 shipped, and it can basically display anything that the van's computer knows. It's like Veritaserum for OBDII ports. 

Like any good project, the first step was drilling a hole….

Add some double-sided tape.

And you're done! Yes, we straightened it out–this photo was taken before we applied the tape. 

We pulled the driver's knee panel off and zip tied the wires out of the way, so this is all you can see on the other end:

The photos don't show it well, but after a few minutes of tinkering we matched the color and brightness of the van's stock cluster. 

Then, after a few more minutes of tinkering, we programmed it to display what we wanted to know. We chose the ScanGauge II over its competitors because it allows user-programmable X-gauges, which basically means you can add vehicle-specific gauges to it.

Here we've got current gear ratio, coolant temp, trans fluid temp, and torque converter slip ratio displayed. This thing has about a million other gauges it can display, though, so we're sure we'll keep tinkering and finding new things to display. It can also show a bunch of what we'll call calculated gauges, which are things it calculates based on a few other readings. Now we have a fuel mileage gage and a distance-to-empty reading, for example. 

After a few trips towing with the ScanGauge II, the news was good: During steady-state cruising with our small enclosed trailer, the transmission temps stay at about 180-190 degrees. Our transmission should have a long life ahead of it.

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