tach and autopilot problems
Our shakedown cruise to Alaska on our 2 1/2 year project continues. We are currently at Campbell River BC waiting for the 14knot current at Seymour Narrows to subside. Thought I'd take this chance while I have internet access to get some input on two problems.
The first one is an intermittenly working tach (more off than on). I have a small alternator(Motorola w/internal regulators) on each engine that just charge my one starting battery. The stbd tach sometimes comes on and then dies after several minutes, although today it stayed on for an hour until I powered up over 1600 rpms. I've checked wires for loose connections and found nothing. I was wondering if perhaps a bad oil pressure switch could cause the problem. I'm sure I can chase it down eventually but thought I'd see if anyone else had any ideas.
The other problem is with my Comnav 1001 autopilot with a fluxgate compass and heading stabilizer. When a big load comes on the inverter, such as a microwave or toaster oven (Heart 3K), it really screws with the heading info. The inverter is a good 7' from the compass. On this one I'm leaning towards trying removing the case grd from the inverter and seeing if that makes a difference. If my memory serves me, we had other problems with this on our old boat and the Heart that could only be solved by doing this. It does mess up our fishfinder and gives a hum on our vhf as well. Any thoughts? Thanks in advance for any input as once we leave here in a couple of hours we probably won't have internet access for a week. Later, Tator
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"Dick "Tator" or Patti" pattitator@yahoo.com writes:
The first one is an intermittenly working tach (more off than on). I have
a small alternator(Motorola w/internal regulators) on each engine that just
charge my one starting battery. The stbd tach sometimes comes on and then
dies after several minutes, although today it stayed on for an hour until I
powered up over 1600 rpms. I've checked wires for loose connections and
found nothing. I was wondering if perhaps a bad oil pressure switch could
cause the problem. I'm sure I can chase it down eventually but thought I'd
see if anyone else had any ideas.
I too experienced a similar problem. I have two 24 volt 150A Ample Power
alternators, one for the start bank and one for the house bank. My tach was
driven from the house bank alternator and would cut out after a few hours of
operation. I talked to the folks at Ample (great customer service, BTW). They
said that the amplitude of the tach signal is based on the amount of changing
current, and that the charging demands of the start bank were typically so
low that the tach signal dropped to almost nothing. I switched the tach to
the house alternator (which always has a higher load) and sure enough the
problem disappeared.
Scott Welch
FirstClass Product Manager
www.firstclass.com
"The person who makes no mistakes usually doesn't make anything"
<<The first one is an intermittenly working tach (more off than on). I have
a small alternator(Motorola w/internal regulators) on each engine that just
charge my one starting battery. The stbd tach sometimes comes on and then
dies after several minutes, although today it stayed on for an hour until I
powered up over 1600 rpms. I've checked wires for loose connections and
found nothing. I was wondering if perhaps a bad oil pressure switch could
cause the problem.>>
Dick,
Most Lehmans and some other engines are set up to turn on the alternator's
regulator by sending power through an oil pressure switch. If this switch
malfunctions, no inverter power and no tach signal. Try jumpering this
switch while underway to see if the tach returns to functioning. Don't
leave the jumper wire on after shutdown, or the battery will slowly
discharge through the alternator field coil.
Mark Richter, m/v Winnie the Pooh
Presently docked in Canajoharie, NY on the Erie Canal and northbound
MaArk's Mobile Marine electrical systems installation, repair and
consulting.