? Sudden overheating?

[KWKloeber]

When the gauge goes high, is the engine cover closed? 
Do you have foil insulation on it **(terminal shorting out)**
(see Ron's previous warning about that!!) 

If it is not already, insulate the temp sender terminal with a small BlueSea terminal cap.

I to G terminals is 12.5V. 
No wire on the "S" terminal, gauge rests below 120'F.
"S" and "G" terminals are connected, gauge reads >240'F.

It APPEARS that the gauge is OK

resistance of the sender is 435 ohms at 97'F.

That APPEARS reasonable for that temp.  That was with the S wire disconnected from the sender correct?

I ran a new wire directly from the sender to the "S" on the gauge.  Gauge still shows >240'F.

Based on #3 on the troubleshooting guide, is the sender shorted (0 ohms)?

What #3 refers to is:  "If you short out the terminal on the sender, the gauge will (**should**) read >240.
You measured the sender (said it was 435 ohms -- so no, the sender itself appears to not be shorted out.)

I don't think they are around any longer.

Along with nearly all other manufacturers (Guest, Ancor, etc, etc,) Teleflex gauges have been gobbled up by SeaStar Marine.  I doubt they can help much beyond what is in the troubleshooting steps.

Remove the S wire from the gauge.  Check the resistance from that wire to panel ground.
  It **should** read the same as the temp sender resistance

[Schulcb]

After removing the S wire from the gauge, the resistance from the S wire to the panel ground (checked using the G post on the temp gauge) IS 970 ohms.  Checking the resistance at the sender again (cold this AM) is 900 ohms.

When the gauge started displaying inaccurate readings it was sporatic with it going from "pinned" high to reading normal.  Then the frequency diminished until it always reads >240.

This morning with the engine cool, when I engerize the panel the gauge reads ~170'F.

Not sure it this tells you anything...

Thanks,
Craig

[KWKloeber]

EDITED

Craig this makes no sense to me. Pinning high is due to zero resistance at the gauge S terminal and you have 970 ohms there.  The R measured on the S wire should be very close to the R of the sender (depending on what gauge S wire you ran.)  However, you are measuring the two Rs by referencing two different grounds (directly to the engine block vs. the path back to the gauge G terminal, therefore, that could account for the difference***. (That might mean your ground up to the panel needs checking/ohm-ing/attention.)  ***Remember when you are measuring R using that method, you are measuring R of the entire circuit (i.e., from the panel, S wire to the sender, the sender, through the engine block to wherever the connection is for the ground wire going up to the panel, through the panel wiring, and to the gauge G terminal.  70 ohms difference corresponds to about 30 feet of 14 AWG stranded wire, so you are definitely in the ballpark given the theoretical resistance of the S wire and return circuit.

Still, the gauge should read a little lower (not pin high) if the R is higher at the gauge than at the sender.

You saw my questions about your engine cover?

After removing the S wire from the gauge, the resistance from the S wire to the panel ground (checked using the G post on the temp gauge) IS 970 ohms.  Checking the resistance at the sender again (cold this AM) is 900 ohms.

When the gauge started displaying inaccurate readings it was sporadic with it going from "pinned" high to reading normal.  Then the frequency diminished until it always reads >240.

This morning with the engine cool, when I engerize the panel the gauge reads ~170'F.

Not sure it this tells you anything...

Thanks,
Craig

[Ron Hill]

Guys : Before you start tearing things apart - spend a few $$ on a heat detection gun and see what the temperature of the engine really is!!   

A thought

[Noah]

I assume Ron is suggesting using an "infrared thermometer" to measures heat, NOT a "heat gun" that creates heat. Both are good inexpensive tools to have onboard.

[KWKloeber]

Guys : Before you start tearing things apart - spend a few $$ on a heat detection gun and see what the temperature of the engine really is!!   

A thought

Ron

Perhaps you can post a link to your info about the engine cover grounding out the Temp switch.  I could not locate it.  Given what was explained so far that's the only explanation I see that makes any sense.

[Schulcb]

Hello All,

Sorry KWKloeber, the gauge is reading those values I quoted above with the engine cover open, and continues to give erroneous (high) reading with the engine cover closed.

The wiring harness with the S wire is 12 gauge, I believe, and the temporary wire I've used to by pass the wiring harness is 14 gauge.  If the ground to the instrument panel is the culprit, wouldn't all of the gauges be giving incorrect readings?

Ron, I do have an infrared temp. gun and it consistently reads ~170 - 175'F.

Thanks,
Craig

[KWKloeber]

Am I correct that if the sender isn't grounding to the engine (teflon tape), I would get a high temp reading?

The gauge **should** pin low if the sender is not grounded to the engine block (or read low if the ground has high resistance.)
When the gauge S terminal is grounded it **should** pin high.

If the ground to the instrument panel is the culprit, wouldn't all of the gauges be giving incorrect readings?

The voltmeter could read OK because there is very low current to the panel gauges, so virtually no voltage loss.

The Tach "reads" the pulses from the alternator (the frequency of the AC output, not the amplitude.)  A voltage above about 7v will drive the tach, so it may read ok.

(I have no clue how your fuel gauge is wired) but it was common for CTY to run a separate ground from the fuel gauge direct to the tank bonding screw, so that may read OK.  You should be able to see if it has a separate ground.

Try checking the panel ground wire - for resistance to the engine block (is that where the ground is  established for the panel?)  You'd need to run a temporary wire back up to the panel to use as reference (or use the old temp sender wire if it is still there.)  HOWEVER, I'm not sure how the panel ground will affect the gauge reading. but I would not **think** it would make the gauge pin high.  That's something I have not run across before.

I find this good for troubleshooting
https://www.harborfreight.com/30-ft-retractable-test-leads-58024.html
I just wish that it was 16 gauge rather than 18.


I presume that your Temp alarm works?  Grounding the engine temp switch S wire to the block **should** sound the alarm.

This keeps pointing to a short to ground in the S wire but there is resistance there.   Maybe an intermittently bad gauge, but that is a huge coincidence that it goes intermittently bad between removing and reconnecting the S wire.

Does she have the Westerbeke black plugs on the harness (at the rear of the engine?)

This is real headscratcher since you already replaced the S wire.

[KWKloeber]

Craig

The more I remotely wrap my feeble brain think about this, the more it leans toward the gauge. 

The Teleflex troubleshooting is checking only two extreme circumstances and nothing in between, like a "norm" midpoint.
It **could** be that the gauge pins high at anything above infinite resistance (when the S terminal is disconnected.)
Or it could read significantly high when the S resistance "says normal."


I couldn't see the forest -- (unless you have access to some resistors in the 50-ohm range to completely bypass the sender,) remove the sender and hook it up to the S and G terminals right at the gauge. 
If she still pins high (and the sender has a reasonable resistance value for the ambient temp,) your gauge is likely kaput. ***

***I say "likely" because it's a boat and we know that there are never any absolutes!

[oldcatsailor]

Had overheating problem screech was coolant pump lock up got back to mooring .removed belt pump was wobbling called Kubota supplier and got new pump installed and problem solved careful ordering pump first one wrong sent photo 2 nd one worked fine.

[Schulcb]

Thanks for "staying in the game".  The gauge is the only thing that hasn't been replaced or bypassed.  I'll order from from CD and report back once installed.

[KWKloeber]

Don't play whack-a-mole with parts.  Confirm, then buy

Remove the sender and hook it up to the S and G terminals right at the gauge.
If she still pins high (and the sender has a reasonable resistance value for the ambient temp,) THEN replace your gauge

[Schulcb]

I'm not sure I understand what you mean by "remove the sender"?

[KWKloeber]

Craig,

I'm not sure I understand what you mean by "remove the sender"?

Remove the temperature gauge sender from the thermostat cap. And use it to follow the troubleshooting steps I said in message #69.

[Schulcb]

Confirmed that it was a faulty gauge.  Bought a replacement from Catalina Direct which resolved the issue.

Thanks for all of the assistance.

Craig