Fixing the Speedometer, Removing ECU

During the test drive, I noticed that the speedometer wasn't working. It had worked fine before I removed the engine. After researching the Helms manual, I needed to get at the speed-sensor on the transmission to figure out what was going wrong. Fortunately I hadn't yet wired up all the BatMon boards, so removing the firewall batteries to get at the sensor only took a few minutes.


Here's the firewall battery rack with two batteries removed to get at the speed sensor on the transmission. I'm pretty happy with how quickly I could remove the powder-coated hold-downs and remove the batteries.


Here's the non-functional speed-sensor. The debug procedure is to remove this and test the voltage at each of the three wires. It turns out I had a bad ground connection (black wire). The original ground came from a bolt on the engine which no longer exists. The black ground wire actually went up the wiring loom all the way to the engine harness connector, so I could fix it there.


Here's the fix for the problem: Find the all-black(no stripe) wire on the engine harness loom just in front of the driver and ground it to the chassis. This ground wire actually supplies the ground not only for the speed sensor but for the ECU. I used an automotive wire splice (pinkish connector) to splice in a piece of 16 gauge wire to a blue ring terminal on the chassis.


Speaking of the ECU. I guess it's pretty useless now, and I can tap into some of its wires to drive lights on the dash or sense other parts of the car. Since I don't want it drawing extra current (probably not much anyway), I decided to remove it. Here is the passenger side carpet pulled away so I could get at the ECU bolts.


Here's the ECU unbolted on the passenger side floor.


Just for yucks, I opened it up to see the inside. I'll probably sell this if there is a local buyer.


After checking a few other electrical items, I noticed that my 12V car battery was actually quite low (11.8 volts). I'm pretty sure it came this way, since the DC-DC converter appears to be working. I'm leaving it on a 13.6 volt float charge overnight (perhaps the weekend) to see if I can get it back to full.

Next up: wiring up all the BatMon boards (spaghetti, here we come!)