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TACH signal from alternator

I'm not saying for anyone to go out and buy one for @alex1234. I'm saying if anyone has an old, or fried, used diesel alternator of the correct years laying around, to pull the pulley on it and send it to him. Actual shipping rates to send something that small over there via USPS aren't that bad. Declare its value as $1 for a used pulley and duty and import taxes shouldn't be that bad. And if Customs Officials open the box to see if somebody's trying to pull a fast one on something valuable - they'll find a used pulley!
 
I got lucky talking to a local starter and alternator rebuild shop. I told them what my issue was and gave them the size of the pulley. the next day they found one and gave it to me free of charge. most rebuild shops that specialize in alternators and such would most likely have tons of old pulleys laying around where someone could sift through finding what they needed. I'm sure there would be a shop similar out there where Alex is located, though I don't know how common a GM style alternator would be out there compared to others in his area.
 
@alex1234 send me a PM with your address and I'll get a shipping quote. I have a pulley here, bought it a few years ago when I thought I had the wrong size pulley on my alternator. Turns out my transmission had been rebuilt with frankentstein parts and that's why my speed to RPM didn't add up. Should be much easier to swap pulleys than messing with the circuit board
 
as the circuit board upgrade project is not progressing....
today i tried to measure OD of the alternator shaft, for have the right pulley for it.
shaft it is practically at the level of the nut. to be sure of OD shaft I would have to remove the pulley.
but it should be a 17mm like the other previous models
but i need to remove pulley also to measure the backspace of pulley

but what shocked me is the pulley ODs

I assumed it was the small pulley for gassers, it's actually even smaller, a billet 50mm OD - 42mm OD on the groove:eek:
 

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@alex1234 I see you have the AD-244 style alternator on there. just out of curiosity does you alternator have a mount on the rear for a support bracket other than the two through bolts visible in the photo you posted? I upgraded mine using a junk yard find of the same style alternator. mine only has the two through bolts and at some point would like to find one that has a rear mount point for a support bracket. not that it might break or anything, just for some extra support in that area.
 
..with tech 1A scantool detected the TACH gap
I increased RPM with scantool to read 2000 RPM at tach...and it reported a reading of 1406 RPM to crankshaft
****600RPM gap*****:eek:

I must been very conservative with my foot on the accelerator over the years...too much😁
in reality I never gave it much importance, I pressed the pedal and went by ear
 
dbrannon79 said:
@alex1234 I see you have the AD-244 style alternator on there. just out of curiosity does you alternator have a mount on the rear for a support bracket other than the two through bolts visible in the photo you posted? I upgraded mine using a junk yard find of the same style alternator. mine only has the two through bolts and at some point would like to find one that has a rear mount point for a support bracket. not that it might break or anything, just for some extra support in that area.
Click to expand...
used 2 bolt only.....as was before
for fir it on engine with minor modification... it's upside down
 
therefore I did some calculations to have it calibrated correctly

I measured the circumference of the crankshaft pulley 600mm
(602mm)...alternator pulley circumference...some proportions
and I found the calibrated ratio is 1:10
1 pulley crankshaft revolution = 10 pulley alternator revolutions
with a deviation of less than 1 RPM

this means that I should have a pulley with a circumference of 188.495mm OD 59.999mm on groove ... a pulley with OD 60mm on groove

diesel pulley has an OD 62mm on groove, this means that with this pulley the TACH would read less RPM than real (about 50-130 RPM less on RPM engine range)

with a gas pulley with OD 56mm on groove, have two, and one measures something over 55mm and the other 56mm (not 57mm as it should) the TACH would read more RPM than real (about 100-250 RPM more on RPM engine range)

perhaps even the diesel pulley could have a lower real OD than declared, and therefore more adherent to the 60mm that would be needed to have the tach calibrated
 
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Just curious if there's a newer better way of getting a tach reading?

I have an old rpm meter that you hold to the center of a shaft - not the handiest thing.

You could also hold it to the side of a shaft and do some calculations.

Keyways really in messed with doing it that way.
 
it would be nice to find another way to calibrate the tach on these rigs. the one thing that always stuck out to me was the need of a larger pulley on the alternator. using a larger diameter pulley makes the alternator spin that much slower and can effect the charging at idle.

just thinking about it reminds me of the older rigs that when you had any accessories on like headlights and you stop at a intersection seeing everything slightly dim out. iirc all vehicles in the era of the 70's and 80's up had this problem.
 
dbrannon79 said:
it would be nice to find another way to calibrate the tach on these rigs. the one thing that always stuck out to me was the need of a larger pulley on the alternator. using a larger diameter pulley makes the alternator spin that much slower and can effect the charging at idle.

just thinking about it reminds me of the older rigs that when you had any accessories on like headlights and you stop at a intersection seeing everything slightly dim out. iirc all vehicles in the era of the 70's and 80's up had this problem.
Click to expand...
I would think, with everything we have available now, something could be made to attach to 1 end of the crank or the other.
The electronic tach I had, wasn't very big and seemed to work fine
 
dbrannon79 said:
the one thing that always stuck out to me was the need of a larger pulley on the alternator. using a larger diameter pulley makes the alternator spin that much slower and can effect the charging at idle.
Click to expand...
Y’all need to concentrate in this point a bit more.

Why did GM bother spending all the money to make the different size pulleys?
It would be much easier and far more profitable for them to just use the gasser one but they didn’t. They could have set the ratio up at any one they wanted for the same cost but instead spent more for doing it where they did.

Change that pulley and avoid the charging hiccups, and avoid the rpm hiccups.

You can run the tachometer using an ESS, Engine speed sensor - it is an Oil Pump Drive with a 2 wires signal that comes out. Then build an adapter. That should only set you back around $600 by time your done.

You can buy aftermarket tachometers that have a sensor that goes on the alternator and a huge hose clamp around the alternator to hold it in place. Then mount the gauge on top of your dash. Those were $400 last time I saw, and reportedly last 4-5 years.

There is another one that is adjustable that you drill part of the bellhousing to install and it reads the flywheel teeth. You program in how many teeth the flywheel has, mount its gauge on the dash and good to go- those seem to last decades, cost around $1200.

From here, prices start getting mighty expensive.
My suggestion- buy the correct pulley.
 
Will L. said:
Y’all need to concentrate in this point a bit more.

Why did GM bother spending all the money to make the different size pulleys?
It would be much easier and far more profitable for them to just use the gasser one but they didn’t. They could have set the ratio up at any one they wanted for the same cost but instead spent more for doing it where they did.

Change that pulley and avoid the charging hiccups, and avoid the rpm hiccups.

You can run the tachometer using an ESS, Engine speed sensor - it is an Oil Pump Drive with a 2 wires signal that comes out. Then build an adapter. That should only set you back around $600 by time your done.

You can buy aftermarket tachometers that have a sensor that goes on the alternator and a huge hose clamp around the alternator to hold it in place. Then mount the gauge on top of your dash. Those were $400 last time I saw, and reportedly last 4-5 years.

There is another one that is adjustable that you drill part of the bellhousing to install and it reads the flywheel teeth. You program in how many teeth the flywheel has, mount its gauge on the dash and good to go- those seem to last decades, cost around $1200.

From here, prices start getting mighty expensive.
My suggestion- buy the correct pulley.
Click to expand...
Aw c'mon Will, we all love to question the GM engineers and over think things. HAHA 🤣😆😂 .. Just joking
 
discussion of alternators and the pulley GM designed for them, has its limits
from 96 the pulley is a 57mm (or less) as gasser they also changed the alternator, I hope
CS-130 was a piece of shit
my yucon, had 3 of this,... last one with very short life
then i go to AD-244...is there from 2012 without problems
 
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