Temperature guage not working

[its fcucked]

Just blown and subsequently changed the engine in my 1994 525 TDS touring. Replacement engine has come from a 3 series TDS 1998. Swap went O.K except the temperature guage isn't working. When you switch the ignition on the guage moves a fraction to cold so i don't think the fault lies there. I've fitted all of the temperature senders from the old head into the 'new' lump and nothing. changed the connecting plugs over where possible and nothing. Checked for breaks in the loom...nothing. Went to BMW and they reckon that the the 2 sensors for the guage are the those nearest the front of the engine.. changed those and nothing. I've checked the voltage at the plug for these and one has 12 volts the other has 3.5
Any diagnostic ideas anybody? don't really like driving around with a newly replaced engine and not really know whats going on? everything else seems to be o.k and working...help!

[billB]

TRY THE EASY WAY OUT 1st: Possible: since all senders checked ok then the ground on the rear of the guage is most likely loose. Remove the cluster and tighten the (6 or 8mm??) nut on the back of the temp guage. This may fix your problem if not let us know then we will tell you about the SI battery..you may have to change that too
good luck
billb