Another tach not working, trying to decipher alternator wiring

[dxulander]

References Reviewed (there were many others but these were the key ones):

Alternator wiring...tach issue

I've recently completed a wiring harness replacement on my 1990 E32-200/Universal M25XP. I was originally inspired to do this due to intermittent tachometer function as well as intermittent starter button failure...(ie. push button, no start). I also bought new gauges and re-fabricated my...

ericsonyachts.org

Tach not working....

My tachometer was previously working a few weeks ago. Engine runs fine, but tach needle dances all over the place. It's not a huge priority to fix because I know how the engine sounds at cruising RPM, but it would be nice to get it working again. Can anyone give me pointers on what to check...

ericsonyachts.org

E32-3 - Another Engine Panel Upgrade - Pt. 1

Here’s my posting of my recent Universal engine panel upgrade. The real nuts-and-bolts of engine panel and wiring upgrades has already been posted, thankfully, by C. Williams and T. Metzger (see CW-1, TM-1). My write-up assumes you’ve already...

ericsonyachts.org

Context: Been on the journey to get the instrument panel fully upgrade/updated (https://ericsonyachts.org/ie/thread...un-begin-starting-w-engine-instruments.20233/), and I've basically got every wire figured out / reverse-engineered on both the cockpit-side and engine-side, have redone everything, including some of the wire-hacks that Christian posted (i.e. start w/o glow). Engine fires up, water temperature is registering reading.

• Cockpit-side: IGN bus and ground bus
• Engine-side: (+) battery bus and ground bus

Problem statement: tach still isn't working. Tracing the "gray" #10 from tach-sender leads me to slot "1" at the alternator. Generic online search seems to show this is an "internal regulated alternator", can't seem to find the make model of this specific alternator, to find the manuals. Plugs 1 and 2 on alternator seems to be connected on the same circuit, and register same voltage as battery when engine not running, running DC. Can't find where my "AC" tap is for the tachometer.

Slightly obsessed, any help appreciated.

 

[G Kiba]

I don't know if this will be any help. I put in a new tach two years ago and had problems with it not working. That is after doing my best measuring the pulley and trying to decipher the number of poles from the info on the unit. In desperation, I ended up trying the different settings on the back of the tachometer to see what would happened. One of the settings looked close to what I expected idle RPM to be. All others were way off or didn't move the needle at all. I kept the setting that was close and it has been working since. I never did figure out how many poles my alternator had.

 

[Christian Williams]

As Grant says, try various settings on the black knob (white arrow). See if anything happens.

Recollection is that Ericson often used 55 amp Motorola internal regulator alternators, if that helps identify yours.

 

[dxulander]

I don't know if this will be any help. I put in a new tach two years ago and had problems with it not working. That is after doing my best measuring the pulley and trying to decipher the number of poles from the info on the unit. In desperation, I ended up trying the different settings on the back of the tachometer to see what would happened. One of the settings looked close to what I expected idle RPM to be. All others were way off or didn't move the needle at all. I kept the setting that was close and it has been working since. I never did figure out how many poles my alternator

As Grant says, try various settings on the black knob (white arrow). See if anything happens.

Recollection is that Ericson often used 55 amp Motorola internal regulator alternators, if that helps identify yours.

View attachment 48238

Yep, I read your post from prior (https://ericsonyachts.org/ie/threads/tach-not-working.18183/post-137659), and turned to all of the tach "ratio" settings, on back of tach. I think primary root-cause, if alt isn't putting out an AC signal, as the sender is connected to DC circuit, conclusion is that it's not a ratio setting.

 

[Christian Williams]

Somebody here will figure it out. Missing Tom Metzger. Metzger? (Never thought I'd say that )

 

[Kenneth K]

The tach gauge itself should have 4 leads: 1. gauge power, 2. gauge ground, 3. alternator signal, 4. light bulb power. If any of the first three are not conducting, the gauge won't work. Even if those three connections are good and powered, the gauge itself could be shot.

 

[dxulander]

The tach gauge itself should have 4 leads: 1. gauge power, 2. gauge ground, 3. alternator signal, 4. light bulb power. If any of the first three are not conducting, the gauge won't work. Even if those three connections are good and powered, the gauge itself could be shot.

Yep, all 4 leads are working, key switch in IGN: gauge lights up, same circuit goes to (+), voltage registering, ground goes to ground-bus. Tact is a brand new tact from defender.com. Debating if I want to go grab another new tach, or put my tach into some other system to test.