[C320-list] Tachometer only works at startup

[Jeff Smith]

I diagnosed mine by turning off the battery charger and discharging the batteries to some degree. Then, when I started the engine, I checked to see if the alternator was supplying any voltage. It should jump up to the 13.5 - 14.4V range. I initially used my Xantrex to see if any current was flowing. You can also back probe the alternator, which I did after the quick check, but be careful. It does not hurt to make sure the alternator is getting a good ground. I did not like the brittle state of my ground wire (grounded to the engine block) so I added a ground buss bar and ran a new ground wire from the back of the block to the buss bar. Now any additional grounds are added to the buss bar and I do not mess with the engine block connection. Also, it goes without saying but I will say it anyway, you should also check the belt tension. 

I sent my alternator to an engine shop but it was not salvageable. If your alternator is bad, I think some on this site have purchased an alternator from Parts4engines.com. Just make sure you get the right alternator. It is very expensive to send anything back to the U.K. (like almost as much as the original alternator purchase). 

Hope this helps,

Jeff

> On Mar 18, 2021, at 5:02 PM, Clay Carter <fclaycarter at yahoo.com> wrote:
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> Thank you Jeff.  New to this subject of electronics:  If the alternator was bad the voltage meter would show it somehow, no?
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> “Be kind,for everyone you meet is fighting a hard battle.” ~Plato
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>    On Thursday, March 18, 2021, 01:56:35 PM PDT, Jeff Smith <jeffreyssmith at live.com> wrote:  
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> Clay,
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> Is it only your Tach or are all of your instruments on the cluster inop? I noticed my tach was operating intermittently (similar to what you suggested). It turns out my alternator was not working. Once I replaced my alternator, I got my tach back. I am less inclined to think this is the case if your hour meter still works. However, to rule that out as an issue, check voltage from your alternator. Especially if your alternator is the original Lucas alternator. 
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> Good luck,
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> Jeff
> ’94, #121
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>> On Mar 18, 2021, at 12:23 AM, Clay Carter <fclaycarter at yahoo.com> wrote:
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>> I have a 1994 Perkins M30.  Tach works for about 2 seconds only at engine startup and then falls to 0.  With engine running the hour meter which is located in the tachometer continues working. Thoughts on what the issue might be?  The tach itself?  Sender?  (Is there a sender for the tach?)
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>> Thanks for your input.
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>> Clay Carter
>> #225 We’ll Sea
>> Alamitos Bay, CA
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