Sending units or gauges

[Vince]

How can I determine what the proper electrical input to the gauges should be from the water temp, oil pressure sending units. I am trying to determine if I need new gauges, or new sending units as the gauges don't seem to be consistent.

[agraziano23]

I'm in the same predicament as you. I'm missing the oil pressure sending unit and the water temp is visibly broken. I'm going with the same maker of the gauges, the water temp is a Faria instrument so I'll get a faria sending unit. The oil gauge has no name on it that's going to be a more difficult. I toiled with the idea of hooking up a potentiometer to the gauge to figure out what the resistance range is but I'm not really sure that's a good method.

[Dave Neptune]

My ywo cents.

Vince & Tony, due to the costs of repairs and the trouble of replacing the engine I suggest that you just bite the bullet and buy new guages for piece of mind. They're not that expensive when compared to the cost of replacing the engine due to failure of a simple guage.
I even have some static guages mounted on my lil beastie for checking while working on the motor or if I'm just not sure of something I can check them.

Dave Neptune

[Vince]

thanks dave,

I am going to get to bottom of this. I guess the safe way would be to replace gauges and sending units, but I'd like to be sure they are the problem first. I guess I am sasking how i cantest them b4 replacinmg.

[David Masury]

I agree with Dave Neptune, replace the sending unit and the gauge as a set.

Teleflex makes pretty good units and not much money and usually available at most retail boat supply shops or onlline. Better yet, see what Don has here on this site for your needs.

David

[hanleyclifford]

If you want to see some really cool gauges, go to "cyberdyne".

[rigspelt]

I'm in the camp that simply buys new gauge/sender pairs if the old ones fail, after some basic testing. There are probably ways to verify sender/gauge matching using resistance testing, but gauges are so useful and relatively inexpensive that I have never bothered with a new old boat.

Hanley's tip: http://www.speedsolutions.net/cyberd...-shipping.html

[Al Schober]

Vince,
I agree with you, I like to know how things work. When I was sorting out my temp gauge, I removed the sender and measured the resistance at various temperatures. This also told me whether high resistance corresponded to high or low temperatures. (Don't recall which it was off hand) Then I took a resistor from one of my boxes of misc junk - I think it was 100 ohm, corresponding to about 155 F. Connect this between the sensor lead and the block, and check the temp reading - 150 F? - close enough. Then just veryify the extremes - open circuit = high resistance, peg the right way? Short to ground = low resistance, peg the other way. A similar attack on your fuel gauge should be informative.

Al

[Vince]

Thanks Al, that's the kind of info I was looking for. Will give that a shot tomorrow.