Strange temperature gauge issue??

[Maine Sail]

My temperature gauge on my Westerbeke 44B Four has been acting up lately and no one at Westerbeke can give me the info I need. I'm trying to trouble shoot the sending unit and the temp gauge but no one at Westerbeke can tell me the cold resistance reading (OHM's) I should get on the temp sending unit and what the reading should be a 180 degrees. I am not one of those who just replaces parts until he finds the problem. I much prefer to trouble shoot correctly and in the proper path. In this instance it would be sending unit, wiring then gauge but the folks at Westerbeke are NO help. Does anyone know the resistance I should see when cold on a temp sending unit for a Westerbeke or Universal temp gauge. The panel I have is the standard Universal or Westerbeke panel with volts, tach, temp and oil pressure. Before anyone states the obvious, yes, I have used my infrared thermometer to double check that the temp is correct and it's running at between 176 and 182 degrees consistently even though the temp gauge consistently says it's running at 220 degrees....

 

[Chris Burti]

Try Seaward Products

The tech support folks at Seaward Products in CA have been very knowledgeable in providing me with this sort of information when I have had just this sort of inquiry.http://www.seawardproducts.com/

 

[Maine Sail]

Thanks Chris..

But it is not one of the Catalina / Seaward panels. It's a factory Westerbeke panel and it uses different gauges than the Seawards do....

 

[Chris Burti]

Doesn't Matter

I'm pretty sure that Seaward doesn't actually manufacture any of their guages or senders. I suspect that they have manufacturers reference material that may provide you with an answer.Most similar guages and senders operate within approximately the same ranges and the info they have may be close enough for you to proceed with your testing.

 

[Maine Sail]

Yes maybe the...

Temp sending units are the same and they'll know the resistance... Thanks for smacking me in the head until I got your point....

 

[larry w]

try this

I had a very similar problem with my Perkins temp. gauge. My system does not use the engine block for ground, rather they use two wires to everything. I had many problems with the gauge until I ran a separate ground straight to the start batt. neg. terminal. problem solved.

 

[Chris]

In addition to the foregoing, all of which is on

the money, the quick and dirty test is:Disconnect the sender. The gauge should read either full hot or (usually)full cold, depending on the type.Short out the sender wire to battery ground (run a jumper). The gauge should read the opposite extreme.If the two conditions do not give an extreme reading, check the harness and gauge for bad connections, you have resistance in there.If the gauge does give an extreme reading both disconnected and shorted, try shorting to engine, not battery. Gauge reading should stay the same. If not, you have a bad engine ground.If all these are good, you have a bad sender.

 

[RAD]

Maine Sail

I have an older Weserbeke 30 and had the exact same problem and did the same thing with infared scanner and tried to figure out which is bad the sender or the gauge, I ended up installing a mechanical water temp gauge and now I know what the temp is without any power and it match's the old gauge in looks

 

[Bill Roosa]

Checking the sender

Chris gave you the display unit checkTo check the sending unit all you need is an ohm meter. Start with a cold engine and connect an ohm meter to the sender. Start the motor and watch for a "smooth" but not necessarily linear, response to the engine warming up. If you see a spike or flat spot then the sender unit is suspect.Chris's observation about 2-wire systems is correct. If you have only one wire to the sender then make sure the "ground" is good by taking it off and cleaning the threads.

 

[Don12364]

Been There - Done That!

Over the last 50 years or so have had several sender failures on various engines both boats & cars.The sender has a thermistor inside and this reads a high value when cold - 5KΩ or above and this rapidly alters to only a few ohms - 180Ω or less when hot. I have discovered the resistance change with temperature is so rapid that it means you get a different reading every time you measure it!In previous cases the sender has failed due to old age or overheating.You will need to buy the correct sender for the gauge as different makes use different thermistor pills.A simple test of the meter is to switch on with the sender disconnected and the gauge should read at the low end of the scale. Then short the sender out and the gauge should read full scale. Gauges are made to tolerate this treatment.If the meter is ok then I guess it must be the sender - or the wiring??

 

[Gord May]

Testing Gauges

Basic Engine Gauge Theory & Testingcruisersforum.com/forums/f14/basic-engine-gauge-theory-and-testing-645.html?highlight=Testing+Gaugeshttp://www.cruisersforum.com/forums/f14/basic-engine-gauge-theory-and-testing-645.html?highlight=Testing+GaugesSender Resistance: cruisersforum.com/gallery...=500&userid=79http://www.cruisersforum.com/gallery...=500&userid=79Temperature Gauges:1. Disconnect Tan Sender Wire from Gauge (Terminal “S”) and turn Instrument Power ON.The Temperature Gauge should indicate ZERO Scale (< Low Temperature).2. Short the Gauge Sender Terminal “S” to Ground Terminal “G”.The Gauge should deflect to FULL Scale (> High Temperature).3. Measure Resistance from Tan Sender Wire (disconnected from Gauge) to Ground.American Temp. Senders will read: 450 Ohms (Engine Cold @ 100 deg. F)or 29.6 Ohms (Engine Hot @ 250 Deg F )European Temp. Senders will read: 281 Ohms (Cold @ 40 DegC) and 22 Ohms (Hot @ 120 Deg C)4. Disconnect Tan Wire from Sender on Engine Block.5. Test continuity of Tan Wire.Zero Ohms from Block End to Gauge End - If not, repair or replace Wire.6. Measure Resistance from Sender Terminal (on Block) to Ground on Block.Should read as per (3) above - If not, replace Sender.