Electromaxx H/0 Alternator and tach issues

[nautikaljeeper]

I have installed an Electromaxx 140 amp alternator and serpentine belt kit on a 2006 Hunter 36 with a Yanmar 3YM30 having the combined VDO tacho & LCD digital hour meter type tach. Before the install the tach worked fine. After installing the alternator the tach is reading higher rpms than it should but seems to be charging normally. WOT is now reading 4800. In my research I am finding that I will have to measure the new alternator and crankshaft pulley to recalibrate the tack using a formula (crank pulley diameter/alt pulley diameter x 8). This info is said to be specific to VDO tachs. Having said that I have since calculated the pulleys and made the adjustments to the tach. What I am experiencing now is that the tach is steady at idle but reading lower than it should being around 600 rpms(I might add this is being measured by a photo tach). Then when I raise rpms the tach becomes erratic and falls to 0 rpms. Is there something I might be doing wrong? Apparently so. Is it some kind of noise interference? This kit from Electromaxx is supposed to be bolt-on and plug-in to the existing harness plug. May I add that bolt-on wasn't quite accurate as some minor fabrication had to be made for factory belt cover to fit. It would be much appreciated if there is someone with knowledge of what I am doing wrong or where to go next.

Scott

 

[Marc14857]

Tach Issue

I have installed an Electromaxx 140 amp alternator and serpentine belt kit on a 2006 Hunter 36 with a Yanmar 3YM30 having the combined VDO tacho & LCD digital hour meter type tach. Before the install the tach worked fine. After installing the alternator the tach is reading higher rpms than it should but seems to be charging normally. WOT is now reading 4800. In my research I am finding that I will have to measure the new alternator and crankshaft pulley to recalibrate the tack using a formula (crank pulley diameter/alt pulley diameter x 8). This info is said to be specific to VDO tachs. Having said that I have since calculated the pulleys and made the adjustments to the tach. What I am experiencing now is that the tach is steady at idle but reading lower than it should being around 600 rpms(I might add this is being measured by a photo tach). Then when I raise rpms the tach becomes erratic and falls to 0 rpms. Is there something I might be doing wrong? Apparently so. Is it some kind of noise interference? This kit from Electromaxx is supposed to be bolt-on and plug-in to the existing harness plug. May I add that bolt-on wasn't quite accurate as some minor fabrication had to be made for factory belt cover to fit. It would be much appreciated if there is someone with knowledge of what I am doing wrong or where to go next.

Scott

I am very sure that the issue is the new Alternator has a different number of poles than the original alternator. Had the same problem a fer years ago. If the new alternator has more poles say 14 instead of 12 the tach will read high or vica versa for fewer poles as counts the number of pulses produced by the poles in each rpm. Easy to fix. Go to the vdo website and download the spec sheet for the tach. It will contain programming instructions to calibrate the tach for the number of poles on your new alternator. I think that I may have posted the spec sheet for the tach a few years ago so you may find it in the archives here as well. Let me knowmifnyou can't find it and I will try to locate my copy.

 

[nautikaljeeper]

I am very sure that the issue is the new Alternator has a different number of poles than the original alternator. Had the same problem a fer years ago. If the new alternator has more poles say 14 instead of 12 the tach will read high or vica versa for fewer poles as counts the number of pulses produced by the poles in each rpm. Easy to fix. Go to the vdo website and download the spec sheet for the tach. It will contain programming instructions to calibrate the tach for the number of poles on your new alternator. I think that I may have posted the spec sheet for the tach a few years ago so you may find it in the archives here as well. Let me knowmifnyou can't find it and I will try to locate my copy.

Thank you for your reply and I may be a bit confused. I thought that is what I have done but I will visit the site and look further into the procedure and see what happens.

 

[Marc14857]

Tach Issues

Just want to make sure that you understand that the calibration is done by programming the tach by entering the program mode and entering the number of poles. No manual calculations are necessary. In effect you are telling the tach that 12 pulses ( or whatever number is right for your alternator) = 1 RPM. The programming mode is entered by accessing the back of the TACH and following the step by step instructions in the spec sheet.

 

[nautikaljeeper]

Just want to make sure that you understand that the calibration is done by programming the tach by entering the program mode and entering the number of poles. No manual calculations are necessary. In effect you are telling the tach that 12 pulses ( or whatever number is right for your alternator) = 1 RPM. The programming mode is entered by accessing the back of the TACH and following the step by step instructions in the spec sheet.

Ok so I guess my question now is how to find the number of poles. To clarify my "manual calculation" what I have done is used the number 12 from the result of the equation I listed and inputed that into the tach. I could not find the spec sheet for the tach in the archives so if you have a copy it would be much appreciated. I will try to find the number of poles from Electromaxx?

Thanks again for your help.

 

[Jalepeno]

This is what I use:
http://tinytach.com/tinytach.php

 

[Mike B]

I also installed the ElectroMaax 140 and like your tach mine is also now reading a higher speed. I was going to attempt to adjust the tach, a VDO, but found it does't have any adjustment pot. I called John at ElectroMaax for his thoughts. He stated that apx 70% of his customers simply find the engine's sweet spot, take note of the new RPM reading and use it from there on in. Not really happy with that as a solution but I don't want to buy another tach just to fix it. Something I'll have to do when I sell the boat though.
Mike

 

[Marc14857]

VDO Tach

Here is the link to the spec sheet on how to adjust the VDO tach. You can calibrate it manually or input the number of poles. It also provides instructions on how to set the tach to a specific RPM if you want to use a strobe. There is no pot adjustment. It is all contained in an IC chip.

http://www.egauges.com/pdf/vdo/0-515-012-037.pdf

Marc

 

[Marc14857]

Nautikaljeeper

I realize that my previous post was not 100% correct as you do need to know pulses per diesel revolution so you do need to calculate the ratio of alternator revolutions to engine revolutions, not just alternator poles. when i changed out my alternator i did not change the pulleys so it was a little easier. Alternatively you can use an inexpensive strobe to manually calibrate as described in the instructions. Sorry for the confusion.


Marc

 

[Mike B]

Re: VDO Tach

Marc, after posting my response I decided to do a search on the topic one more time. Found the same info you shared in your link and will give it a try tomorrow.
Mike

 

[Mike B]

Made the adjustment to the VDO Tach on my Yanmar today. It's still reading a little high when I run max throttle in neutral but within 200 RPMs. Still have to do a test run under load but from what I can see it'll be very close to what I originally had and good enough for me. Other than fumbling with the tach panel assembly while pushing the button and turning the key, not to mention reading the instructions again, it was an easy fix.
Mike

 

[nautikaljeeper]

Nautikaljeeper

I realize that my previous post was not 100% correct as you do need to know pulses per diesel revolution so you do need to calculate the ratio of alternator revolutions to engine revolutions, not just alternator poles. when i changed out my alternator i did not change the pulleys so it was a little easier. Alternatively you can use an inexpensive strobe to manually calibrate as described in the instructions. Sorry for the confusion.


Marc

Yes that is what I was referring to in my first post in regards to the ratio. Somehow the ratio number that I came up with does not equal the pulse setting that is imputed into the tach for it to read correctly. Anyhow in trying different pulse settings I have found one to be correct for my alt and pulley kit. I think it would helpful if Electromaxx would give pole count on there product. Nowhere did I find that info. Much thanks for your help and all is well.

Scott

 

[nautikaljeeper]

I also installed the ElectroMaax 140 and like your tach mine is also now reading a higher speed. I was going to attempt to adjust the tach, a VDO, but found it does't have any adjustment pot. I called John at ElectroMaax for his thoughts. He stated that apx 70% of his customers simply find the engine's sweet spot, take note of the new RPM reading and use it from there on in. Not really happy with that as a solution but I don't want to buy another tach just to fix it. Something I'll have to do when I sell the boat though.
Mike

Yes I would not be happy with that solution as well. I had to chuckle as I thought to myself with that kind of product support how can you be successful in selling a product. Gives me a sour thought vs "a sweet spot".

 

[nautikaljeeper]

Made the adjustment to the VDO Tach on my Yanmar today. It's still reading a little high when I run max throttle in neutral but within 200 RPMs. Still have to do a test run under load but from what I can see it'll be very close to what I originally had and good enough for me. Other than fumbling with the tach panel assembly while pushing the button and turning the key, not to mention reading the instructions again, it was an easy fix.
Mike

Mike in several adjustments that I had made to my tach I might be correct in saying that if you lower the pulse # by 1 you would lower that number by 200. At least I found that to be true in my case. And I agree it is an easy fix.

Scott