Power Surge

[larman]

I have a 1987 Searay 410 aft cabin. I have been having an issue with power surges when I turn certain things on at the helm. The one that is most troubling involves the temperature gauge. When I turn for instance the navigation lights on my temperature will jump 20 degrees setting off the alarm. Is there any thing that I can do to maybe isolate the temperature gauges so they will not be subject to power surge issues?

 

[ScottC]

It seems to me that the effort would be better spent trying to identify the root cause. Certainly it wasn’t this way from the factory! Unfortunately, I don’t know enough about this area to give you troubleshooting guidance. Hopefully, others will!

 

[C lectric]

I will guess that you have a poor connection or two in the power supply to the panel.
Could be either or both the + & - leads. THe connections must be clean and tight.
What it sounds like to me is as you turn on another item there is more voltage drop due to the extra current drawn through the excessive resistance caused by the poor connection thus the Vdrop.

Go through the feeds, especially the main one for the power and check them.
Do NOT ignore the ground.
Start there.

 

[larman]

Ok will do, thank you for the replies.

 

[STB]

How long are the reading off before returning to normal? Or are they off as long as the other device is on?

What other symptoms are there?

Do we know if the gauges normally read correctly, e.g. have they been compared to resistance on sender?

Did the boat come to you this way? Did the problem suddenly develop? Did it develop slowly over time? Didnit appear at the same time another change happened or was made?

The odd thing is, unless I'm misremembering (which is very possible) is I think the resistance of most temp senders goes down as temp goes up and are part of the ground path for the gauge. So, I'm a little surprised the temp moves up. I forget if the gauges are a bimetallic ammeter, or similar, or if they are volt meters across a resister forming a voltage divider. But, either way, I'd expect a lower voltage to mean a lower temp.

The only reason I mention the above is that, if the guages stay off vs bouncing, and it is an old problem, tou msy want to check that the gauge is getting a real +12 and not in series with something else.

But, as others have said, 99% of the time it is corrosion, a bad connector, etc.

 

[rslifkin]

I'd blame the grounds personally. If the sensor doesn't have a dedicated ground wire to the gauge, then a bad shared ground from the gauge will cause bad readings. With a temp gauge, typically they'll read high in my experience.