[NelsonP]

Hi,

Please need advise on the following problem. While on anchor, as soon as I am operating the aft fresh water wash pump to clean the boat, the VHF switches off. Obviously it has to do something with load, but do not have a clue.

Other DC instruments do work normally. It is only the VHF that play such tricks. When this takes place, the genset is operating, and the "smart chargers" are on.

Any ideas as to the reason that such problem occurs will be appreciated.

Thanks,

[NYCAP123]

Originally Posted by NelsonP

Hi,

Please need advise on the following problem. While on anchor, as soon as I am operating the aft fresh water wash pump to clean the boat, the VHF switches off. Obviously it has to do something with load, but do not have a clue.

Other DC instruments do work normally. It is only the VHF that play such tricks. When this takes place, the genset is operating, and the "smart chargers" are on.

Any ideas as to the reason that such problem occurs will be appreciated.

Thanks,

I'd look for the DC power line to the pump to be crossing the power line to the VHF or they may be on the same breaker. Best bet would be at or just before the breaker panel. I'd also check that both are grounded. Would this happen to be an Azimut?

[C4ENG]

I would start with a ground test for possible ground faults with the pump.

With the breaker off to the pump, Take a voltage meter and set it to continuity. Put one end of the meter to any power lead to the pump, if not two or three power leads, one at a time. Put the other lead to a Known ground surface of the vessel. You should have no continuity, operating the pump or not.

If you do..find where the wire has failed from the power source and correct it.

[NelsonP]

Thanks for the post,

Well I doubt if it is that, as I had a look behing the circuit panel already and everything was neatly placed. Actually, the circuit breakers have some distance from each other as the VHF is on 12V and the water pump is on 24V.

In any case I shall have a look again and check the wiring. Its a Sunseeker not an Azimut.

Thanks,

[NYCAP123]

Originally Posted by NelsonP

Thanks for the post,

Well I doubt if it is that, as I had a look behing the circuit panel already and everything was neatly placed. Actually, the circuit breakers have some distance from each other as the VHF is on 12V and the water pump is on 24V.

In any case I shall have a look again and check the wiring. Its a Sunseeker not an Azimut.

Thanks,

Theoretically, they should have no effect on each other unless the pump is somehow drawing the power from the VHF which should only be possible if there is a connection in the lines. I assume from what you say there is no drain on other 12V items.

[chesapeake46]

A place to start is here:
This sounds like a voltage drop at the VHF radio when the large load of the wash down pump comes on.
That could indicate a less than perfect battery, inverter or less than really tight termination somewhere.
Using a meter at the VHF terminations, set to the 12 Vdc scale, watch the voltage while you have some one turn the pump on.
An analogue meter is better for this test than a digital meter.
The analogue meter's needle will deflect with the voltage.
Digital may not respond fast enough to catch the drop.
The test is best done near the VHF radio for a true reading of the voltage where it is furthest from the source to indicate voltage drop.
If it is the voltage drop, I would begin with tight terminations and battery/inverter load test.

[NYCAP123]

Originally Posted by chesapeake46

A place to start is here:
This sounds like a voltage drop at the VHF radio when the large load of the wash down pump comes on.
That could indicate a less than perfect battery, inverter or less than really tight termination somewhere.
Using a meter at the VHF terminations, set to the 12 Vdc scale, watch the voltage while you have some one turn the pump on.
An analogue meter is better for this test than a digital meter.
The analogue meter's needle will deflect with the voltage.
Digital may not respond fast enough to catch the drop.
The test is best done near the VHF radio for a true reading of the voltage where it is furthest from the source to indicate voltage drop.
If it is the voltage drop, I would begin with tight terminations and battery/inverter load test.

The voltage drop is obvious from the result, but what about the fact that one is on the 24V system and the other is 12V?

[chesapeake46]

Originally Posted by NYCAP123

The voltage drop is obvious from the result, but what about the fact that one is on the 24V system and the other is 12V?

****, I missed that part....
Could be loose terminations on a common Neg or ground..
****** connections reek havoc

[K1W1]

Originally Posted by chesapeake46

Digital may not respond fast enough to catch the drop.

Hi,

You are correct in adding this as I have had personal experience with this little nugget of frustration years ago.

Analogue Meters are normally moving coil of moving iron meters, Digital Meters can show full voltage on a DC system that can barely power a light bulb. It is because they are so sensitive.

For quick testing on DC systems I use a good old fashioned Test Light when ever I can.

[NelsonP]

Thank's a lot guys,

It seems that a loose connection is the case. I shall drop to the boat in the morning and do some tests. I suspect the connection with the VHF unit, a Simrad RS8400 is the problem as it has these pins, female to male connection, and since it is an open boat I remove the unit every time, I am not in.

Thanks, I ' ll keep you posted.

[chesapeake46]

Nelson, is it possible that the 24 volts is a pair of 12 volt batteries connected in series from which the 12 volt system is taken from one of these batteires ?
This would be a common point and possibly indicate a cell going bad in a battery or a place to look for the bad termination also.