2100SD High Temp Alarm

[JPut]

I have a 2002 2100SD with 5.7 engine, my problem is during normal day light operation the temp gauge is stable at 175, but as soon as I turn on my Nav or Deck lights the temp indicator immediately starts to rise and the High Temp Alarm sounds. I know the engine is not overheating so it appears that I am getting an electrical feedback through the electrical system! Has anyone experienced this type of problem, or can someone tell where to begin to resolved the problem, I was thinking it might be a problem with the Temp Gauge or a short in the instrument assembly.

Suggestions please,

JPut

[pascavone]

I believe the gauges never lie....

You have a short, and the alternator is maxing out with the large draw on it as it grounding out.

the alternator under full load will stretch the belt and bog down the engine.

try this:
1. pull the fuse to the lights you have problems with and then try it.
2. loosen the alternator belt off the engine and then run the engine, turn on your lights. see if the temp gauge reacts. the raw water pump will not turn with the belt off or water pump, so only run it unit the temperature gauge rises.
3. you can put a volt meter on the alternator and see if it pushing out 80amp... which is maximum.

[ss3964spd]

Interesting symptoms, JPut.

Though I disagree that the alt is "maxing out" I do agree with #1 to aid your troubleshooting. Perhaps you've already tried but can you duplicate the symptom using any other accessory on the boat? Meaning, the stereo, the GPS if you have one, fresh water pump if you have one, the anchor light, etc-etc. How about raising and lowering the outdrive while watching the temp gauge for movement? Anything else what will draw current.

If it turns out that turning on the deck or Nav lights are the only two things that will reproduce the symptom I would start by removing the light bulbs, one at a time, from each fixture and re-test. The nav lights for instance; remove the port light, test, replace and remove starboard, test, remove both, test. This is going to tell you if the problem is located behind the helm or back in the engine compartment.

Remember how the wiring is run. You've got a 12V cable running from the engine compartment up to the helm and into the fuse box, as well as a ground cable. Also know that the audible alarm does not function straight off the backs of the gauges, but instead is triggered by the engine computer.

Dan

[shrew]

Not much to add, but more to hijack. My temp guage does the same thing. though not to this degree. I do see that wehn my volt guage takes a dive, my temp also rises. It seems to do it for most everything at the helm; drive trim, tab trim, I particularly notice it with the fridge, and most other 12v devices. The less I have running the higher my voltage and the lower my temps.

I've already replaced both fuse boxes at the helm, all fuses and all connectors. I'm considering running a new ground to the fuse boxes.