I needed to change out a faulty water temperature sensor. Well… at least I think it was a sensor issue. First order of business: collect data and diagnose the issue. That required obtaining serial infrared laser gun data and comparing that against fluctuations with sensor data that was being sent to the water temp gauge. For the most part, engine heat infra red data was steady at 160⁰ F and varied between 155⁰ and 160⁰. Engine water temp sensor data is relayed to a circuit on an AETNA gauge on the “dash” that reports tachometer rpm, system voltage, water temp, oil pressure, and hours. Water temp readings were jumping all over the map from 145⁰ to 210⁰. My estimate of the issue: bad sensor.
What’s more, when the sensor reports a 208⁰ F reading or more, faulty or not, it sets off an alarm. That event generates a handy fight or flight response within the sapien cohort aboard. In general, alarms do that and for the most part alarms are meant to awaken the crew to the fact that bad juju is stomping about, eh?
So, I commenced preparations to replace the sender. First step: put on mechanics togs which are nothing more than what were perfectly good jeans and a hoodie that I’ve splotched with paint, varnish, dirty oil, clean oil, caulk, and blood. Yes… blood. It seems to me that if I work on any of the multitude of mechanical devices on the boat, SHE always manages to bite me and I bleed. It’s never much of an issue, and I’m sure she does it with affection, but I do keep bandaids handy whilst working on the engines, generators, pumps etc.
Changing out a sensor is a simple enough process. Collect the 3/8 inch wrench to unscrew and remove the positive sensor wire. A 7/8 inch box wrench to unscrew the sensor, a plastic garbage bag to use to protect anything that might get wet with antifreeze, a bucket to place in front of the hole once the sensor is removed before you can plug the hole with the new sensor, a new sensor, multiple rags, multiple pairs of heavy duty 8mil non-latex gloves, face mask and goggles, and a headlamp with extra battery.
The process is strait forward. First corollary to prevent a coronary: one must be careful to release any pressure present in the cooling system anywhere… a most important step to take before unscrewing and removing the old sensor. If that step is ignored, antifreeze will squirt out the hole with force spraying antifreeze on the engine, on your cloths and in your mouth and eyes if they are not closed. You might ask how I learned about that…
Armed with all the paraphernalia that I collected, I lay down in front of the engine, removed the sensor wire, unscrewed the sensor to hand tight and as the last thread released a cascade of antifreeze gushed out. Now I will admit, I was expecting this even though I’d taken steps to release the cooling system pressure. It wasn’t nearly the cascade that it could have been… so I stuck my thumb over the hole, slipped the new sendor over the hole and screwed it back in, tightened it and replaced the sensor wire. All in all it was a 30 minute job and I only lost about a 100ml of antifreeze. Clean up took about as long as everything else leading up to torquing the new sender back in place…
Tested it we did, and it did seem to work, but we never got the engine over around 130 degrees. The good: the sender / AETNA readout matched much closer to the heat gun data. So far so good.
Well, that was yesterday. Today we motored from Delta Marine by Sidney, BC, over to Roche Harbor and once we cleared customs we carried on and anchored in Garrison Bay. The bad: Once the engine got up to operational temp… of around 160⁰… the sender / AETNA readout was still jumping all over the gull dern place from 145⁰ to 210⁰… with an occasional alarm firing off even though the engine was only at 160⁰. So… there you have it… the gauge itself is the culprit. Toast I say.
Hmmm… the process for replacing the gauge will be an interesting journey… I’ll just have to find a nice exotic location to ponder my next steps. A nice cold beer might assist my contemplations…
The better news: Delta staff found the leaking issue with the NAIAD stabilizer system, replaced 4 hydraulic lines and it now performs flawlessly.
Salish Sea Cruising With Blair, Les, Leo, and Bliss 