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wes brown
wes brown,
Category: Boat
Satisfied Customers: 6
Experience:  installer/ technician at georges marine electronics
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I have Cummins 450C engines and all of a sudden, both tachs

Customer Question

I have Cummins 450C engines and all of a sudden, both tachs stopped working. I can understand that one may go due to maybe a sensor, but both at the same time? I had a tech look at it and he says the tachs are working but no signal from the sensors. Reluctant to call Cummins because there is a $300 charge just to get to the boat and they don't always fix the problem.
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else the Marine Mechanic should be aware of?
Customer: No
Submitted: 1 month ago.
Category: Boat
Expert:  wes brown replied 1 month ago.

The sensor for the Tach is in each engines alternator.

what voltage are your engine batteries reading?

Customer: replied 1 month ago.
The voltage reading the last time I used the boat (last week) was 12V while running, which seemed a little off because normally they would read a charging voltage of 13+ Volts. The interesting thing here is that both tachs stopped working at the same time, which would suggest some common element to both.
Customer: replied 1 month ago.
I am anxious to get a resolution to this as the boat is now sold, so please respond asap.Thanks.
Customer: replied 1 month ago.
Expert:  wes brown replied 1 month ago.
the alternator have to have sufficient voltage to run the a.c. tap probe (teach sensor).
if one alternator has been down, the other would circulate voltage to the other while running.I suspect both a lternators need repair
Customer: replied 1 month ago.
I'll be heading to the boat tomorrow and check it out...thanks.Chris
Expert:  wes brown replied 1 month ago.
are any other gauges not working?
Customer: replied 1 month ago.
No, all other gauges are working properly.
Customer: replied 1 month ago.
Wes,Thanks for the advice. It turned out to be that the engine battery switch was turned off and the voltage must have been low. When I allowed it to charge, the tachs worked fine.

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