Jumpy Tachometer

[ndutton]

Jerry,
I second Shawn's offer. If shipping gets pricey, I believe I'm closer.

[roadnsky]

Shawn & Neil-
Thanks guys, great offer. I really, really appreciate it.
(Man, I'm tearing up here )

I think I'm close though...
I checked the belt tension and it was good. So not belt slippage causing the jump. (Thanks for the suggestion though, SB)
I'm almost certain it's not the alt now. Nor the tach gauge.

I ran a jumper from the ALT output (Orange Wire) to the positive side of the starter (bypassing running to the ignition) and ran her up. When the alt kicked in, the Tach "jumped" once and then settled in. I didn't see another jump.
Problem is, I ran out of time.
I was running late for a big "Family" (spelled In-Laws) Dinner, so I had to button her up before finishing my testing.
I'll go back tomorrow and finish running thru some paces and report back...

PS - Don, I may still call you in the morning to discuss and tap your wisdom, if that's ok.

[ndutton]

Man, that's screaming loose connection to me.

[roadnsky]

Man, that's screaming loose connection to me.

Neil-
I KNOW it wasn't a loose connection because I've been through those connections with care and prudent circumspection.

What I really think it is/was...
The Orange wire may have had a short or bad conductivity. (best bet)
I've replaced almost all of my wiring, but was reluctant (yes, and cheap) to replace that beautiful Orange wire because I didn't want to buy a roll to replace a 4-foot run.
Another possibility, which I will look into tomorrow, is that by leaving the output of the ALT running UP to the Ignition (sorta old style wiring) instead of going straight back to the charging system (starter post) there might be something going on resistance-wise in that ignition/coil path. (Steve, were are you?!)

The good news is that I feel like I'm really close here...
AND I'll end up with a new and improved wiring from the ALT.
I promise to report back tomorrow with findings as this may help a lot of other wiring issues yet unknown out there...

[sastanley]

Jerry..my thought on the comparison was to get another alternator in there to see if yours may have some issues and causing undesired interference. I have an aftermarket tach on my boat and it is rock solid, so hence the suggestion...no worries though - I know we all like to tinker.

[off topic question]
Since you mentioned cheap and wiring..
I am just beginning what will ultimately be a complete re-wire of my boat. Neil and I have been chatting offline regarding mast re-wiring, which is my current winter project and one he tackled a few years ago. Anyway, when you guys buy your marine wire, are you buying entire rolls? I guess in the long run that would be cheaper for most projects than buying "x" feet for each application. For example..I am not currently planning to re-wire the entire boat this winter, but I am thinking now, why would I only buy 50 feet of duplex & 50 feet of triplex wire to re-wire the mast, if someday I have to make new runs all over the boat anyway? Spend money now to save money later?
OK, I think I just answered my own question...off to genuniedealz.com! Carry on.
[/off topic]

[roadnsky]

Shawn-
Yes, you did answer as I would have advised.

Go and sin no more my son...

[rigspelt]

[off topic question] Since you mentioned cheap and wiring.. I am just beginning what will ultimately be a complete re-wire of my boat ... when you guys buy your marine wire, are you buying entire rolls?[/off topic]

I should have bought whole rolls three boats ago. Finally woke up and smelled the dollar signs. I also gave up trying to find marine wire colours other than red, black or white and learned how to label wires carefully.

This all applies to DC wire. When I rewired AC I bought two rolls of good marine triple cable because I could not find a custom length supplier of the stuff around here. Thought I could sell the rest at cost to someone else rewiring a boat locally - no luck.

[sastanley]

rigs, thanks for your feedback...I have NO AC in my boat so it is not a factor..but I still appreciate it.

I research and research and research, so much so I am sure I over research..sometimes I just need to pull the trigger....maybe by next week, I'll have ordered some DC wire. I am re-researching the Moyer PDF of DC A-4 wiring tonight, so I can maybe get some of that in my next order too...

[roadnsky]

Done

Ok. Done. Success.
Did the tests and have solved the jumping problem.
Also, by tracking this down, I solved a problem I wasn't even aware that I had.

First thing I did was fire up and watch the volt gauge to know when the Alt kicked in and crossed fingers and toes that that pesky jump wouldn't start.
Watched that damn gauge for 5 minutes. Yippee! No jumping! Move on...

Hooked the old Orange wire back up (going thru the ignition) and fired back up.
Alt kicks in and bingo. Jumping disco tachometer!

Re-wired a permanent jumper (Alt to Solenoid) and went out for an extended 45 minute engine run. There was never a jump at all RPM's.

Some interesting voltage readings to ponder...
At the ALT Output Terminal - 13.68
At the IGNITION post at the end of the Orange wire - 13.20
At the Positive POST of the SOLENOID with the Orange wire run to Ignition - 13.18
At the Positive POST of the SOLENOID Bypass the Orange wire and use ALT to Solenoid jumper - 13.68

So, I'm theorizing the Orange wire had enough resistance (or even a short) to cause enough voltage drop to effect the tach?
Or possibly the length of the run from Alt to Ignition and back to Solenoid?
The Ignition switch and positive feed from Solenoid to Ignition are new (within the year)
The ORANGE wire is the only old original wire left in the ignition circuit for reasons I mentioned earlier.
(Sorry Don. Should have taken your advice about replacing all of that old harness )

The real value in tracing this down is that I feel I'm getting a better Alt to battery voltage AND possibly avoided a short (or worse?!)
causing a shutdown or non-start. (Most likely in a 30K gale on a Lee Shore)
Sure hated to throw away that pretty Orange cable but decided a red one in the proper gauge with an easy path to follow does the job too.
(Yes, Rigs. I'm also slowly giving in to labeling instead of color coding too)
The "Purist Devil" on my left shoulder still keeps whispering to go buy colors though!
Anyway, I'm ruling success and will enjoy my shiny new tach.

Can't officially close the thread (it's not mine anyway) until Gary (gmilburn) hopefully reports back to us if he solved his jumpy issue from October.
AND I'm sure you sparky geniuses may have a better theory of what was actually going on in that old Orange path...

[roadnsky]

One more...

After a conversation with Don I thought it necessary to post one more time with a little more explanation/info and a thought...

Don asked if I had an ammeter...
No, there isn't an ammeter in the cockpit gauge cluster. It's very possible there was one originally with the boat and it was removed.
The gauge of that Orange wire leads me to believe it was there at some point. That might also explain why it was wired that way when I bought the boat.
(That Orange wire terminated at the Ignition post with the Red positive wire from the solenoid)

Don... "I can't recall what kind of boat you have, but your voltage readings are reflective of the "Catalina 30 syndrome". The Catalina 30 has an 18 foot wiring harness between the engine and the cockpit which means that the charging circuit has a total run of 36 feet in the round trip between the alternator and the battery bus on the starter solenoid. This unusual length alone will frequently result in voltage drops much more than your 1/2 volt. Add to this unusually long distance the fact that there are three eight-pin Medallion disconnects in the harness through which the charging circuit must pass two times (for a total of 6 male/female pin connections) before getting back to the battery bus, and you can easily see why the Catalina 30 has chronic charging issues."

My boat is a Ranger 30. And it is interesting how the original wiring was. The wiring harness is somewhat similar to the C30...
It's approximately a 12-foot cable run with TWO Multi-Pin disconnects. The interesting part is that it could easily be a 3-foot run as the crow flies!
Those cables were even "wrapped" in a back-n-forth loop and wire-tied together to hold the excess wire.
Maybe the original run was designed to go to a more aft/port position, since that is where my original Depth Gauge was? (It's where I have the new Tach now)

Anyway, I mistakenly left that Orange wire run (Alt to Ignition) in when I re-wired (and put in fuses) using the MMI Drawing.
I mistakenly thought that was how it was supposed to be. (Although I questioned why alt power would need to go up and then back)

When I was troubleshooting the Tach, I read the instructions for installing the (MMI) API 55A alternator because I'm planning to go with the larger alt soon.
In those instructions it's noted that "If you do not have an ammeter, or the ammeter does not work, you can connect the output terminal of the API directly to the big battery cable on the starter solenoid."
That gave me the idea to try the jumper and the rest you know from my long-winded explanation above...

So, my reason for posting is to make sure some of you understand that the long run from Alt-Ignition and back to Solenoid is un-necessary IF you don't have the ammeter. I know this wisdom is mentioned in other threads but thought it bears repeating since some may also mis-interpret (as I did) the MMI PDF Drawing that we use to re-wire.

Again, the DC experts could certainly give us better explanations...

[sastanley]

Again, the DC experts could certainly give us better explanations...

I think you just did Jerry...nice work!

[rigspelt]

Again, the DC experts could certainly give us better explanations...

I'm no expert, but when I rewired the boat last year I got rid of that ammeter in the cockpit ignition panel, eliminated that long alternator output wire, and replaced it with a very short cable to the starter solenoid and thence (big word alert) to the positive terminal on the engine start battery. http://www.moyermarine.com/forums/showthread.php?t=2727

So Jerry, I think you found the same kind of problem I had with that failing slave starter solenoid: bad connections in old circuits. Good work.

[rigspelt]

On re-reading this post, I've been pondering principles for this pesky jumpy tach thing. These are musings from an amateur boater who has lived through 3 used boats, not a professional marine engineer. I've only experienced it once on our first boat, but it was a nightmare. You can imagine my relief when I first fired up the engine after the big refit on this third boat and saw a nice, steady tach needle.

1. Draw complete schematics of a boat's wiring. Start with one based on the batteries and charging system (the heart of the system), and then branch out to include sub-schematics for the engine, ignition panel and house wiring. Those drawings take time to make, but they are essential for troubleshooting wiring. Take advantage of a rainy dockside day to work on the schematics with nice music going in the background. Put on work clothes, then get down and crawl into every nook and cranny, wearing glasses with little LED lights on the frames (but don't let anyone see you wearing them). Along the way, I suspect most owners of old boats discover wires, connections and parts that need updating.

2. Revising old wiring is a time-consuming but very worthy project on an older boat. Shorter and simpler appeals to me, but within sound marine electrical practices. Getting professional advice for best practices in marine electronics is not easy for average boaters.

3. A jumpy tach in an older boat can mean a mechanically faulty electrical connection in either a component or a wire. If in a component, then the easy way to identify it is to swap in a new component. Start with the cheapest ones , and the ones most likely from the schematics to be able to make the tach jumpy. Tachs are expensive, so just clean their terminals and check the cylinder number setting first, unless someone can loan you a reliable tach to swap in as a check. From the few stories I've heard, tachs can be the problem, but usually aren't.

4. The old-fashioned design for alternator wiring on our 70's vintage sailboats apparently was to run a long output wire from the alternator aft to an ammeter in the cockpit, and from there double-back forward to all other systems that draw from the alternator, including recharging the batteries. While that worked for decades in many boats when loads were lower, I get the sense that the modern style is to make the alternator output cable as short as possible, and then draw current for subsystems like the engine, ignition panel and house selectively in dedicated fused circuits. The modern approach seems to reduce opportunities for problems like the one described in this thread by eliminating the ammeter aft and replacing it with a voltmeter, and then running the alternator output directly to the battery via the starter solenoid. Electricity does not seem to like long runs, or at least it is harder to keep electricity flowing cleanly over long distances.

These are just early morning recreational musings of a hobbyist over coffee. Your mileage will vary.