Engine temperature gauge packed up

[Peter R]

Just set off on a cruise today, and after i'd been going for a bit noticed that the temperature gauge wasn't working. Engine seemed happy enough so I carried on. 1.5 hours later, the gauge still hadn't got off the mark, but I have a tank full of hot water, so I know the engine did warm up.

 

Me thinks the most likely culprit is the sender, but I guess it could also be the gauge - anyone know off-hand how to prove which?

 

In case it's relevent, engine is a lister LPWS3.

 

Peter

[alan_fincher]

I guess you've checked the wire is connected at each end ?

 

It certainly can't hurt to put a multimeter on the resistance range between sender terminal and engine housing. I've no idea what I'd expect it to measure, but if it's completely open circuit, then I'd say the sender is shot. I'd expect you to get a different resistance reading between a hot and cold engine.

 

I'm not sure if it's legitimate to touch the sender wire onto to engine casing, and see if the meter jumps wildly. I don't think you would damage the meter, but it might be better to do it with something offering a resistance in place. (I'd not be surprised to be told this last suggestion is dumb - it may well be!......)

[RobinJ]

Just set off on a cruise today, and after i'd been going for a bit noticed that the temperature gauge wasn't working. Engine seemed happy enough so I carried on. 1.5 hours later, the gauge still hadn't got off the mark, but I have a tank full of hot water, so I know the engine did warm up.

 

Me thinks the most likely culprit is the sender, but I guess it could also be the gauge - anyone know off-hand how to prove which?

Normally (negative earth, single wire) temperature gauge resistance reduces as temperature goes up, so connecting lead to engine (-ve) should make it go full scale. Easy to have a wire come off at either end, but sensor is probably most likely fault, can measure resitance with a meter, open circuit indicates its given up!

[Sir Nibble]

Or alternatively, Take the wire off the sender and connect it to earth, (the engine). With the ignition on, watch the gauge, if either having the wire connected to earth or left disconnected sends the gauge up, it's the sender. It usually is.

[Peter R]

I guess you've checked the wire is connected at each end ?

 

I hadn't last night as it was gone 7pm when I stopped, and at that time was more interested in dinner than poking around a hot engine!

 

Checked this morning, and sure enough a wire had come off the sender (which actually has two wires). 30 secs with a pair of pliers and the spade connector now stays on!

 

Thanks for the replies - I just couldn't think last night how it worked - I think the brain's on holiday as well!

 

Peter

[alan_fincher]

I like the easy ones!