Ok, cheers for all
Went onboard this afternoon, started the engines up and...............still the same
Anyway, we moved her accross the harbour to the winter berth for easy access and did some further investigations (albeit only on 1 engine)
As suggested (and because easy!) first step was to ground the temp sender to the block. Bingo! Guage comes to life!
Is my reading of that correct in that the problem must
Second step was to remove the temp sender (drained the system first) - the bit inside looks like a lump of copper - probably because it is?
gave it a wipe
sat and looked at it over a cuppa
Decided to see if connecting the temp sender back up (and turning both the batteries and ignition on
) and then dangling it into a cup of hot water did anything. Nope.
Then thought maybe it needs to be grounded - found a bit of wire and grounded it. Nope. Swapped the terminals over. Nope.
All told a good 5 miinutes in the hot water. and the copper end got hot enough not to want to hold, albeit not taking the skin off hot. Fortunately
question is - would testing the copper end of the temp sender in a cup of hot water actually give any results? If so would seem (to me!) that the problem is simply the temp senders....and therefore time to buy a new one and see what happens, before buying
a 2nd for the other engine.
(my understanding is that the temp sender operates from simple expansion of the metal - no idea how the electrickery knows though
with dissimilar metals inside brass? copper and electrickery could there be any electrolysis
inside? even though no air? - science stuff not my forte
BTW I can now identify the thermostat housing