2008 RZ4 display

[.NOBODY]

I have absolutely no display. Volts, Oil Pressure, temperature, nothing. All I did was change a battery. Then the SpeedSet. Now I have nothing. Any suggestions?

[ptige]

For sure check fuses. But once in a great while my 2007 display loses communication. There are two or three electrical bulkhead connectors on the bow end of the engine on top with locking tabs and levers to actuate them. So with the boat off I CAREFULLY disconnect and reconnect each. Might be worth a try.

[.NOBODY]

Thank you ptige, you were correct. I was fretting over here. Alls good. Thank you!!!!!! X10

[IDBoating]

We've had this reported by a couple of folks. Hint: Most electrical connectors are "self-wiping". The contacts slide over each other during connection and disconnection, wiping away contamination in the process. True even for gold contacts... they don't chemically corrode but they can get physical debris on them which can act as an insulator, or if large enough physically hold the contacts apart. Add in the rather high vibration environment of a boat (or being directly on the engine!) and connectors can "lose contact" over time. The easiest way to "service" them is to do exactly what you did: Simply disconnect and reconnect each one. Doing so costs nothing, takes very little time, has almost zero downside risk, and many times magically fixes such gremlins.

While I'm at it: The second most common electrical problem has to be ground terminals. In our 24Ve, Tige wisely used stainless grounding terminals for the harness wiring but there are still a few spots (such as battery terminals and connectors) that can corrode over time. Starter terminals are notorious for this too. Even if the starter's own terminals are corrosion resistant, the (usually copper) lugs on the heavy cables are delighted to corrode for you! (See Statue of Liberty for an example of how copper corrodes.)

Related (and somewhat personally embarrassing) story. A couple of years ago our 1994 Case 580SK loader/backhoe was getting progressively harder to start. Its battery was aging, and the weather was getting colder, so I attributed it to the battery and replaced it with a fresh diesel-ranked battery (can't remember the exact Group number but it's ~50% larger than a typical Group 24). I thoroughly cleaned the battery terminals AND the battery lug connectors during the install. Didn't help. Once in a while the engine would start, and once started it would restart reliably, but those initial cold starts were more miss than hit. When it didn't start, I could hear a relay chattering somewhere. The location of the noise clearly indicated it wasn't the solenoid, but there were some socketed Bosch relays in the area so I replaced all of those. No fix. I have this machine's factory service manual (about five inches thick) and the more I dug the more relays I found! Finally, finally, I found what appeared to be the Rosetta Stone of the electrical system, a 70A master relay that switched main power to basically everything except the starter itself. I could feel it chattering, no question it was the problem. Found a replacement at NAPA and installed it. Zippo. No fix.

WTF?!? Turning the key to "ON" lit up all the console lights. The four banks of worklights worked too. Horn worked. Everything electrical worked. The ONLY thing that didn't work was starting the engine... turning the key to "START" caused the main relay to chatter, and of course the lighting all dimmed since the starter was pulling down the battery voltage. All very expected, except that the engine didn't start and the relay was chattering.

OK, when all else fails, back to first principles. I looked up the 70A relay spec sheet and got its pull-in and hold voltages. I put my Fluke DMM across its coil terminals and turned the switch to "START". Sure enough, the voltage dropped to just below the hold voltage, which explained the chattering. Yet when in the "ON" position everything read 12-13 VDC as expected. The battery was new and fully charged, and the electrical system worked perfectly, except when trying to start the engine the voltage dropped too far. Bad connector running to the relay coil? The factory manual schematics showed the coil's circuit was really simple: Straight from the battery, through the keyswitch, to the coil. I measured the switch's contacts and while they didn't have unreasonably large resistance, I replaced the entire keyswitch anyway just for good measure. Still no fix.

I ended up working my way back along the wiring harnesses, checking voltages in both "ON" and "START" positions. Eventually I was all the way back at the heavy battery cables. On the backhoe end, the voltage drop was there. But on the battery end, no voltage drop. If you know anything about Ohm's Law, this means that voltage drop is occurring across the battery cables themselves. Bad cables? Nope... their resistance was super low, in the milliohm range. What's left? Ah... the negative cable (actually a heavy braid) bolts directly to the machine's steel frame. I'm sure that was nice and shiny at the factory, but after a couple of decades it had taken on a rusty exterior. I measured the resistance from the battery end of that braid to the machine frame, and got about 0.5 ohm. Doesn't sound like much, not enough to affect most electrical systems on the machine, but when the starter is drawing 50+ amps the voltage drop is (50A * 0.5R =) 24 volts! Obviously that's more than the battery voltage so the battery scales down under load, but you get the point. Almost all of the battery's voltage was being dissipated in that braid. The resulting drop dimmed the lights, was nowhere near enough to turn over the starter, and was also not enough to keep the main relay engaged so it started to chatter.

This was a definite "forest for the trees" situation. I should have backed up, thought about it for a while, and realized that the key was voltage. But every new discovery seemed like it HAD to be "the answer" so I just kept plowing forward. I suspect had I just cleaned up that grounding terminal I could have been done in 10 minutes for zero dollars. Instead, I replaced multiple relays, cleaned countless contacts, installed a new keyswitch, and ringed out the whole wiring harness. (My fix for the grounding terminal was to disassemble it, use a Dremel tool with wire wheel to get all surfaces down to bare shiny metal, reassembled it, and coated the entire thing in petroleum jelly to prevent corrosion.) The "good" news is I had basically inspected and/or replaced the entire electrical system, so things should be good for a while!

The moral of the story: Corrosion of electrical contacts, large or small, is a very real thing. It can lead you on some wild goose chases. When things look "wonky" on an older or corrosion-likely environment (read: boats!), it never hurts to confirm your voltages and, thus, your grounds. Yet another reason why I think every boat should ship with a basic DMM.

(Tune in next week for more true confessions in our next heartrending episode of "Backyard Boat Mechanic". )