ALTERNATOR TACHOMETER ???

[MIDNIGHT RIDER]

Many years ago, I installed an ?Autometer? diesel tachometer in my truck.

Gauge face says "AUTO GAGE", then "2308", and goes up to 6 (000).

This is basically what I have :

http://www.amazon.com/exec/obidos/ASIN/B000CIJ4AM/ref=nosim/modsearchcom-20


But it looks exactly like this one, except diesel :

http://www.amazon.com/Auto-Meter-23...9SS6GS/ref=pd_ts_auto_49?ie=UTF8&s=automotive

I couldn't find the actual one I have; it may be obsolete???

This unit has a two-wire cord that terminates in a sensor-gizmo that "straddles" the seam between the two halves of my 1985-model alternator.

From what I see, the large-case 3G alternators lack this "seam".

Where on the 3G should my tach sensor be positioned ??


On the same note, on the Dodge/Cummins alternators, it is common to attach the tach wire(s) to something inside the alternator, rather than the sensor being clamped to the outside (one of my Dodge/Cummins has a VDO tach wired thus, but by the previous owner); is this also possible on the Ford alternators ??


Is it possible with the style of tach that I have to connect the wires internally ??



Thanks.

 

[Al_E]

[/URL]attach the tach wire(s) to something inside the alternator, is this also possible on the Ford alternators ?? Yes its possible with a ford alternator. It is called an AC tap. You have to attach a lead off one of the stator poles usually at the rectifier. Not shure if this works with your AutoMeter tach, but it works real well with Vdo tachs.http://www.egauges.com has online instructions for many brands of gauges.

 

[Pino2234]

[/URL]attach the tach wire(s) to something inside the alternator, is this also possible on the Ford alternators ??


Yes its possible with a ford alternator. It is called an AC tap.

You have to attach a lead off one of the stator poles usually at the rectifier. Not shure if this works with your AutoMeter tach, but it works real well with Vdo tachs.http://www.egauges.com has online instructions for many brands of gauges.

This does work on Ford Alternators? I have the 3G Ford Alternator upgrade from a ford taurus. Do you have any more info on this?

I might buy a new Tachometer from Autometer or I have one from Banks that came with my turbo kit that I want to see if it'll run off the alternator.

 

[MIDNIGHT RIDER]

I have since discovered that there are two styles of alternator-pick-up tachometers.

The one on the wife's truck, a VDO, actually has a wire that taps INSIDE the alternator on one of the three terminals.

the kind on my truck has an external "reader" that is clamped astraddle the seam/center of the alternator and counts the magnetic impulses or whatever.

It is my understanding that the two are specific to their use and without being an electronic genious, connecting the one style inside the alternator is not feasible.


I read somewhere of someone making their own brain-box gizmo and modifying a plain old SUN Super Tach II to pick up the signal from inside an alternator.

 

[Pino2234]

I have since discovered that there are two styles of alternator-pick-up tachometers.

The one on the wife's truck, a VDO, actually has a wire that taps INSIDE the alternator on one of the three terminals.

the kind on my truck has an external "reader" that is clamped astraddle the seam/center of the alternator and counts the magnetic impulses or whatever.

It is my understanding that the two are specific to their use and without being an electronic genious, connecting the one style inside the alternator is not feasible.


I read somewhere of someone making their own brain-box gizmo and modifying a plain old SUN Super Tach II to pick up the signal from inside an alternator.

Since your post, I bought an aftermarket tach from Pep Boys and hooked it up to the Stator/S terminal on a 3G alternator. My truck idles at 2200 RPMS and when I rev it up it goes up accordingly. So it is a tachometer signal. I dont know what kind of signal tachometers pickup so I can alter it.

 

[TWeatherford]

I know this is a really old thread, and anyone that was posting in it has long since figured it out or gone a different route for a tach signal. However, I searched high and low online and could find no other example of someone using a 3G alternator for a tach signal, so thought I'd post my experience here in case anyone is looking for it in the future. It was frustrating to read all the threads where people were trying to use their alternator for a tach signal (essentially free) and all that anyone had to say to help was "just spend $50-200+ for one from Dakota Digital, TinyTach etc and it'll be easy."

I wanted to use my 3G alternator for a tach signal for several reasons. 1. is because I was convinced that it is possible. 2. is because I didn't want to buy a sensor. 3. is because I didn't want to come up with an oem looking/durable way to mount a sensor. 4. I have auber instruments gauges for boost, pyro, engine temp, oil pressure, and fuel pressure, and they have a similar looking tach that can handle a variety of inputs, so buying it allows me to have a uniform look to my gauges. I will always have an alternator on my truck, so if I can use it as a tach source I will always have a tach sensor working.

Ultimately, I hooked into the stator wire as described and it works perfectly. I have a digital tachometer from auber instruments, which has two modifiers (A and b) that can be programmed in to adjust the signal properly: displayed reading = measured reading x (A/b). When I first hooked it up the gauge read over 7000 rpm at idle. I used a $9 app for my iphone (search "Engine RPM" in the app store, pretty neat app, and will work for my chainsaw and other engines as well) which picked up the engine rpm pretty well to calibrate it, and so far have settled on A=1 and b=18. Since both A and b can be anything from 1-9999 I can fine tune it as much as I want. Note: these values for A and b won't necessarily work for anyone else, particularly on this forum, because this is in my 97 with a 12 valve Cummins in it. Crank and alternator pulley diameters will affect what A and b need to be.

 

[laserjock]

That's pretty neat. I started reading this and immediately thought, why not just an optical switch (sensor) and a white line. If it malfunctions, you wipe the grease and dirt off the sensor and repaint the line.

Of course picking the signal off the electrical side will work too. Are you picking the frequency up from the ripple or pre-rectifier?

 

[TWeatherford]

That's pretty neat. I started reading this and immediately thought, why not just an optical switch (sensor) and a white line. If it malfunctions, you wipe the grease and dirt off the sensor and repaint the line.

Of course picking the signal off the electrical side will work too. Are you picking the frequency up from the ripple or pre-rectifier?

I'm picking it up from the stator wire. As far as I can tell from the wiring diagrams I've dug up, it hooks right up to the stator internally.

I should mention, many tachometers probably don't have enough adjustment for picking up this signal. But it can be done with the right gauge.

 

[BDCarrillo]

That's pretty neat. I started reading this and immediately thought, why not just an optical switch (sensor) and a white line. If it malfunctions, you wipe the grease and dirt off the sensor and repaint the line.

Of course picking the signal off the electrical side will work too. Are you picking the frequency up from the ripple or pre-rectifier?

I considered the optical pickup by hacking a Harbor Freight optical tach with lcd readout. It'd have to look at the crank pulley, harmonic balancer, or torque converter since it's not adjustable.

The factory tach is driven by a 2 wire AC inductance (may not be the right word) sensor. Plenty on Amazon for a couple bucks but I haven't had time to fiddle with one.

The factory gauge wants to see a ripple for each tooth on the IP gear, and it does the math from there.

 

[Pino2234]

....I have auber instruments gauges for boost, pyro, engine temp, oil pressure, and fuel pressure, and they have a similar looking tach that can handle a variety of inputs, so buying it allows me to have a uniform look to my gauges. I will always have an alternator on my truck, so if I can use it as a tach source I will always have a tach sensor working.

Ultimately, I hooked into the stator wire as described and it works perfectly. I have a digital tachometer from auber instruments, which has two modifiers (A and b) that can be programmed in to adjust the signal properly: displayed reading = measured reading x (A/b)...

TWeatherford,

Which auber gauges do you have in your truck? I am looking into getting the same gauges. They have 2 different tachometer units and I'm guessing you got the one with a "progressive shift light".

I've just rewired my alternator and am now set up to pull from the stator wire.

Do you have any pics of them installed?