Testing my temp gauge

[guy48065]

My temperature gauge hardly moves--if at all. Before I put this up for the winter I'd like to test the sensor & gauge.
Can I just remove the sensor and put it in hot water? I'm guessing there will be water behind that sensor (open system). Just let it run into the bilge?

 

[Scott Danforth]

first, check the ends of the wire at teh gauge and sender (tan wire)
check the ground at the gauge

most likely its corrosion on the terminals

then check resistance of the sender. should be a 230-30 ohm sender (most in the US are)

 

[Grub54891]

You can test it in a pot of hot water without running the motor. Be sure to hook up a go ground and keep the connector on the top.

 

[guy48065]

You can test it in a pot of hot water without running the motor. Be sure to hook up a go ground and keep the connector on the top.

Engine off, key on...annoying alarm ON.

 

[Grub54891]

I

Engine off, key on...annoying alarm ON.

get that, but it will show you if the gauge is reading. I often get annoyed at squaking people but do my best to ignore them.
or just put a temporary pipe plug in the motor if you are running it.

 

[Horigan]

The alarm is likely driven by a separate oil pressure switch, not the sensor that feeds the gauge.

 

[guy48065]

The alarm is likely driven by a separate oil pressure switch, not the sensor that feeds the gauge.

Yeah it's normal but loud, continuous, and real annoying.
My other boat just beeps once as a self-check, then silence.

 

[guy48065]

I thought the 'standard' sensor output varied from about 240 to 40 ohms?
I bought a 200 ohm rheostat to test the gauge and wiring. At first when I jumpered the pot in place of the sensor the gauge didn't budge off the pin. I unplugged the gauge and checked the voltage on the 3 wires with a dmm. Seemed ok but I'm not sure what it 'should be'. Plugged the gauge back in and restarted the motor. Now it moved up to 100*. Subbed the pot back in place of the sensor and now can get the gauge to sweep. It would seem the problem was at least partly dirty connection to gauge.

Sensor measures about 450 ohms when motor is warmed up. Sensor terminal is bright brass and sensor body has continuity to ground. Shouldn't this be reading ~150 ohms on a warm motor?

 

[nola mike]

Sensor measures about 450 ohms when motor is warmed up. Sensor terminal is bright brass and sensor body has continuity to ground. Shouldn't this be reading ~150 ohms on a warm motor?

for a standard faria/teleflex gauge. I believe some vdo gauges (maybe others) have a different scale

 

[Jeff J]

First step is to check the connections.

A pot of hot water works well if you have a good thermometer to compare readings throughout the scale or just want to see if the needle moves. Water boils at 212 degrees with some variance for barometric pressure just to find out if it’s working and semi-accurate without a separate thermometer.

I used a heat gun once just to see if one was working when I didn’t have a way to heat water.

The alarm can likely be unplugged while troubleshooting.

 

[Grub54891]

Sometimes I want to give up. I suggest something and get ignored, then someone says the same thing.

 

[guy48065]

Sometimes I want to give up. I suggest something and get ignored, then someone says the same thing.

Deja vu...

 

[guy48065]

I verified power, connections and gauge operation by connecting the rheostat with alligator jumpers. Then I measured the sensor R and continuity to ground with a DMM. I don't think several hundred ohms is right so I'm waiting for a Quicksilver replacement to arrive early next week.

Once I have it in hand I can then compare indications against a good thermometer, before installing it.

 

[guy48065]

Just a quick update...

My Quicksilver temp sensor measures 800 ohms at 70*F. same as the one on the boat so I guess the sensor is fine after all.
Which now puts the thermostat at the head of the 'suspicion' line.

This is my last weekend on the water. I'll put in a new Tstat during winterization. Testing will have to wait till spring.