engine not reaching running temp

[marshie001]

my car has been running at no more than 40 degrees since i got it, i know that its hotter than that but its not showing on the temperature gauge, i noticed recently that the sensor on the side of the water pump was broken so i replaced it today hoping to have cured it but it didn't!
did i replace the ecu sender? or was it the correct sender, but something else is at fault?
im stuck now, its an '89 200 te by the way!
engine temp doesn't seem extremely hot or cold but i would like it working just so i know :roll:

 

[Mikesmerc]

Sounds like a faulty thermostat Marshie, sticking open when it should be closed until the engine reaches the desired temp. Cheap fix and an easy job.
Mike

 

[jberks]

How do you know its running at the right temp? - Its a lot more common for the temp to be genuinely down than the gauge to be wrong - have you checked the stat? At that age I would expect it to be playing up - or has it been replaced already?

 

[marshie001]

hhhmmmmmm??? i was thinking thermostat, but ive just swapped the wires over from the other sender and its now showing 80 degrees!!?? could anybody clarify what the senders are and what colour wires should be on which sender please?

any help appreciated