Crazy water temp transmitters

Hi!
I have a 110 2.5NA, recently my water temp sensor packed up (thanks to mechanic who turned the flat blade and destroyed it). Hate driving without knowing the temp of the engine. The temp gauge is working fine though.

Replaced it with PRC6663 - WATER TEMPERATURE TRANSMITTER and found that the needle would not go over 10% of the white area. After maybe two hours it went to about 20% of the white area. Thought something was amiss. Checked the wire and connection which was ok.

Replaced the PRC 6663 with 560794 - WATER / OIL TEMP.TRANSMITTER and this time something really crazy happens which is:-
On starting the engine yesterday from cold, the gauge slowly rose up. So I switched it off and this morning at 5:30AM, started my 110 and the gauge shot to 50% of the gauge in less than a minute, funny. After a small drive of less than a KM, the gauge was showing the needle at the end of the white area. Went for my morning walk for an hour and returned and started her up again and up the needle goes. This time I took a 2 KM route and guess what the needle enters the orange area.

Can someone explain what the hell is happening. Dont have the first transmitter part number. The above transmitters are brand new and the temp gauge is working fine, the cables & connectors are all ok.

On LR series.com I saw this:-
PRC6663 - WATER TEMPERATURE TRANSMITTER (supposed to be for 2.5NA)
560794 - WATER / OIL TEMP.TRANSMITTER (using right now)
PRC2505 - THERMAL TRANSMITTER OIL OR WATER

Can someone please tell me which is the exact one? And why this is happening.

PRC6663 is the one for the 2.5NA, 2.5TD and 2.5P, as you have found there are a few to choose from but I can confirm this is the right part. Who made your new one, it could be faulty.

On top of the old one what colour was the plastic and is the new one the same colour, if they are OEM parts they will be marked for easy identification, if not they might have a part no. stamped on it somewhere - it might not be a LR part no but any motor factor should be able to cross reference them for you.

Now, the question is, was your 110 always a 2.5NA Diesel - it may have started life as a V8 or something in which case the sender may be from that.

The next problem, based on your description of events it seems to me like the sender or guage may be goosed because with your PRC6663 fitted you got some funny readings, did you use any PTFE or sealant on the new sender that may be causing grounding issues?

The next thing is, do you still have the old one? It may still be fine, I have saved a few senders and thermalswitches and things by sticking a piece of copper down the side of the old broken spade (if need be drill it out a little) then catch it with some solder - sender fixed.

Also, if you have the old one, get a multimeter on it and all the new ones and measure the resistance of them all - so they are all about the same leave them indoors somewhere slightly warm together overnight so that they all equalise in temp. Does the old one and PRC6663 match more or less?

Thanks for the info. Replaced the faulty one with the PRC 6663, its stamped on the transmitter. Now the temp very gradually climbs up to 10-15% of the white area. Will do another long run and check. Sadly threw away the old transmitter.

Will order a few 6663's and check. Funny as before the gauge & transmitter were working perfectly till the transmitter broke. Was and always been a 2.5na.