Tach quit working

[Brockwaykid]

So, yesterday i was charging my truck after having a dead or near dead battery for the past few weeks. I started it, and noticed the tach wouldnt move. I recently changed the fuel filter assembly, and may have done somthing with the wiring behnd it. (6.5 diesel) Could it not work because of the low voltage? It worked great before this.... Not sure what else could be the cause. Any ideas?

 

[someotherguy]

Man...I'd have to check the manual to be sure, but I think the tach on the diesel is driven by...the...alternator? I'll check and edit back. Probably doesn't matter for this question but it usually helps to post what year/model along with the engine.

EDIT - yup, the "I" terminal on the alternator is where the tach signal comes from. I don't have any troubleshooting info for it, but once you deal with your croaked batteries and have some in there with a strong charge, and still don't have a working tach, I'd suspect the alternator or wiring. Remember the alternator isn't meant to charge up dead batteries; it's just meant to do minor recharge after starting and to supply power to the vehicle while running. Using it to repeatedly charge up dead batteries after a jump is hell on an alternator.

Richard

 

[Brockwaykid]

Man...I'd have to check the manual to be sure, but I think the tach on the diesel is driven by...the...alternator? I'll check and edit back. Probably doesn't matter for this question but it usually helps to post what year/model along with the engine.

EDIT - yup, the "I" terminal on the alternator is where the tach signal comes from. I don't have any troubleshooting info for it, but once you deal with your croaked batteries and have some in there with a strong charge, and still don't have a working tach, I'd suspect the alternator or wiring. Remember the alternator isn't meant to charge up dead batteries; it's just meant to do minor recharge after starting and to supply power to the vehicle while running. Using it to repeatedly charge up dead batteries after a jump is hell on an alternator.

Richard

Ok, I wiiggled the terminal on the alternator and started the truck up and its back working. I now know i had my knee on the alternator when i changed the filter assembly. thx for the help!