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Old 09-25-2010, 05:36 AM
BrockHubbard
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Can't get water temp gauge to work

Help! I can't get the water temp gauge to work on my '97 PS 205 with LT-1. After reading many of the threads on this forum, I've tried to troubleshoot step by step.

Checked dash gauge. Replaced sending unit on engine block with original part from Indmar. Confirmed wiring between the two is sound.

All the pieces seem to be working individually, but when I'm on the water, the gauge won't budge from 120. I "know" the engine is getting hotter than that...

Any ideas?
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  #2  
Old 10-12-2010, 02:10 PM
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Table Rocker Table Rocker is offline
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There is a possibility that the sending unit is not well grounded to the block. Most sending units are shipped with an electrical conducting sealant on the threads. If during installation something like teflon tape was used to prevent leaks a poor ground could result.

You might try running a jumper wire from a good known ground and holding it against the side of the sending unit to see if it changes the reading on the gauge. If the reading changes, the sending unit body is not conducting a good ground from the block.

I hope this helps. Good luck!
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Old 10-13-2010, 09:38 PM
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ahhudgins ahhudgins is offline
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Quote:
Originally Posted by BrockHubbard View Post
Help! I can't get the water temp gauge to work on my '97 PS 205 with LT-1. After reading many of the threads on this forum, I've tried to troubleshoot step by step.

Checked dash gauge. Replaced sending unit on engine block with original part from Indmar. Confirmed wiring between the two is sound.

All the pieces seem to be working individually, but when I'm on the water, the gauge won't budge from 120. I "know" the engine is getting hotter than that...

Any ideas?
What temperature IS your engine running if you "know" it's not 120? First off, use a infra-red thermometer and check the engine temperature right on the sensor. You could have a bad thermostat that is causing the engine to run at 120 degrees and your guage is reading correctly. I wouldn't waste my time trouble shooting a gauge problem until you know what your actual engine temperature is. My 95 uses a 140 degree thermostat and my gauge never got above 120 this weekend because the lake water was 60 degrees. If you find out that your gauge is reading incorrectly, you can look at this link. Scroll down the page.
http://mastercraft.com/teamtalk/showthread.php?t=38088
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Old 10-19-2010, 11:41 AM
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supturb89 supturb89 is offline
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Quote:
Originally Posted by Table Rocker View Post
There is a possibility that the sending unit is not well grounded to the block. Most sending units are shipped with an electrical conducting sealant on the threads. If during installation something like teflon tape was used to prevent leaks a poor ground could result.

You might try running a jumper wire from a good known ground and holding it against the side of the sending unit to see if it changes the reading on the gauge. If the reading changes, the sending unit body is not conducting a good ground from the block.

I hope this helps. Good luck!
So you should not install the sending unit with teflon tape? The previous owner of my boat had installed a "new" sending unit using it and my gauge didn't work correctly. I have since installed a new sending unit (with tape) and gauge. I have yet to confirm if it works properly but the gauge no longer pegs to the right like it was. You can see my problem here:

http://www.mastercraft.com/teamtalk/...ad.php?t=38088

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  #5  
Old 10-21-2010, 04:19 PM
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It is my understanding that any time you are installing a sensor that works by conducting to ground on the block you should use "sensor safe" thread sealant. "Sensor safe" basically means it conducts electricity well. If your temperature sensor is not well grounded to the block it cannot do it's job properly by providing accurate electrical resistance from the ground to the gauge.

Teflon tape is non-conductive, but it still might work if the threads cut through enough of the tape to make good contact with the block. An easy test is to run a jumper from a known good ground to the base of your temperature sending unit and see if your gauge moves at all.

PermaTex and others make several "sensor safe" thread sealants available at any parts store.

I hope this helps.
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