Wednesday, July 31, 2013

Good News, Bad News Part 2

Good news everybody, the Porsche is finally registered!

The other good news is I can finally charge the car without having to open the hatch and the hood.  I installed this spiffy outlet where the gas tank fill spout used to be.  I also got a nice 12 gauge cable so I don't have to worry about overheating the wires anymore.

Now for the bad.  I also had my first breakdown!  I was driving to work and I suddenly lost power.  Luckily I had enough momentum to easily coast into a parking lot.  I realized the voltage on the battery was way low and quickly remembered that I haven't charged the auxiliary battery in about 80 miles!  I conclude that the power to the controller was so low that the brownout feature on the microcontroller shut it down before it started malfunctioning.  My kind and loving wife picked me and the battery up, I hooked it up to the charger, and took the jeep into work.

After work I pick up the battery and my wife drives me back to the Porsche.  I plop the battery in and away I go.  I'm about 7 miles from home and after 5 miles, the car starts shutting down again.  Now I'm not feeling so good because the voltage still reads okay.  I figure out that if I take my foot off the pedal, the controller seems to reset and I am able to limp home.

After thinking for a while, a friend comes over and holds the laptop for me while I drive.  The same problem keeps coming up, and luckily I get a clue from the RTD program.  When I lose power that the controller sends restart info to the RTD program, so it appears that the controller is momentarily losing power.  When it regains power it goes into "high pedal lockout" mode.  The controller will sense if you have your foot on the pedal when it starts up and won't allow the PWM signal to start until you take your foot off.  That explains why I can lift my foot off the pedal and keep going.

So now, what's causing this?  I've got a few theories and I try running a dedicated wire straight from the battery to the controller.  Luckily, this seems to work!  I drive 4 miles and have no problems compared to at least a dozen restarts in the previous 4 miles.

There's a relay I put in to power all the stuff I added (controller, pumps, fans, etc.) and it turns on with the ignition.  I've had problems from the beginning that the instruments seem to have a bad ground or something.  A fresh 12.5 volt battery only reads about 11 volts.  The headlight motor doesn't work either (forums tell me that anything less than 12 volts will cause this to not work) and when the headlights go on, the voltage drops even more.  In fact, it seems like turning on the blinkers would cause the controller to cut out.  I'm thinking the voltage gets low enough that the relay loses power and flips off momentarily.

I've known I need to fix this for a while, and it seems like now is the time.  I checked all the ground connections, and those seem to be good.  I look at the fuse and relay box and find a couple of loose wires!  Unfortunately, it is not obvious at all where these go, but it doesn't appear that they have anything to do with grounding or the headlights.  I snoop around for a while, and suddenly I see this!

Gah!  I'm pretty sure this is one of the 12v power supply lines going into the fuse and relay box.  This must have been loose for a while and the poor conductance built up heat and eventually fried this connection.  I have no idea how long it's been like this, and to my knowledge I've never messed with these connections.  I'm not sure how I'm going to fix this but I'll have to reroute power to the fuse box.  Hopefully this is the problem!

Let's end on some good news.  I've racked up 235 miles so far, so I've almost saved an entire tank of gas!  I can feel the savings rolling in!

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