We found the same on Rick's car when checking it after fitting the new blend motors. Initially it was reading 19 degrees, which with the engine running and a nice hot pipe, seemed a little on the low side. Wiggling the connector on it and it dropped to -20, then with another wiggle started to read 50+ degrees which seemed about right. So it does appear that the connector is the weak point.

Just managed to remove the cursed o rings from my car (Look east and spot the blue cloud - that'll give you a location!)

They were really crusted and flat but they've clearly been done before as the front edge of the under trim panel has been attacked in the past. Thanks for the tip on tightening and then untightening the screw - worked a treat!

One question - has anyone got any tips on how to actually get the new rings on the metal pipes. I got the old ones off with a small screwdriver pretty easily but space is severely compromised. I have removed the top binnacle and fiddled with the heater ducting but am really struggling to get access - it really is a piece of crap design.
I want to clean the join up nicely but I've stopped for the evening now before I torch the whole **ing vehicle.

Thanks in advance ;)

Also - just received an update on the sensor I had on back order from John Craddocks (about 2 weeks ago).

They want £80+postage as they had to 'outsource' supply! Predictably I've cancelled the order - that's extortionate IMO

Craddock are invariably more expensive than others I have found

You need skinny hands and go in from underneath. It's fiddly getting the new rings on, but can be done. Did you remove the duct or just shove it out of the way? I always cut it off as high as possible so the lower part can be pulled out and then put if back with duct tape (probably the only time duct tape is ever used for what it is intended for)

Thanks for the replies. Skinny hands would be great but that's never going to happen - I drive a RR coz it fits me lol
I haven't been able to remove the ducting and was reluctant to cut it in half but I think this might be the way to go (why oh why didn't they make it two piece in the first place????. Out with the vibrating cutter thingy at the weekend as I'm working tomorrow :(

Less of a hurry now as I've just opened the o ring packet and I've only got 1! I think I assumed there would be 2 in a pack but that would make far too much sense. I mean, as if any one is ever going to just replace 1!!!

Ahh, genuine ones then. They are sold singly compared with Allmakes ones that come in a pack of 5???

Be careful when cutting that you don't cut into the alloy coolant pipes behind. It has been done before, no names because he knows who he is......

Finally got a bit of time (and patience!) and got the O rings on and the back plate screwed up. I replaced the original screw with a M5 allen head screw that I got a driver onto quite easily. I gave the pipes a good wiggle as I went - it was a bitch to get started as the rear bracket/plate floats around unless you can get a hand on it but after a false start (cross threaded!) it is all now in place.

For now, I've chickened out and will fill her up tomorrow so am praying for no leaks. Seriously can't believe LR made this service item so ridiculously difficult to get at - even a slightly redesigned air duct would have made it 100 times easier!

I had a bit of a measure over the weekend as I found a 10k NTC thermistor in one of my boxes of bits.

The internal temperature sensor is 10K NYC, but it appears the heater core one I have here on my test rig is maybe 20 or 22k NTC.

I didn't get around to testing the evaporator or outside temp sensors yet, but I'd day they will be one of those 2 values

Thanks Marty, no amount of "wiggling" has got my heater core sensor responding properly. I may try removing / reinstalling next. Is it relatively easy to desolder the thermistor and replace a new one, do you think?

Rgds, Rob

To answer my own question, no, it's a sealed unit

If you've got the thermistor, why not just try poking the wires into the plug and tie wrapping the naked sensor to the pipe? That will at least tell you if it is a sensor or wiring problem.

I don't have a thermistor, but I had a jumper across the plug the last few days to see if the system might be tricked into thinking it was a balmy plus 80 and time to put the air con on, but no dice. So I'm not convinced it's the sensor. Am a bit behind plan on the A/C diagnostics as I was doing a Defender oil and coolant change over the weekend, and the weather got cold again :o)

Could you test the sensor in a pot of hot water with a multimeter attached?

Yes. Set the meter on the Ohms range and the hotter it gets the lower the resistance. Hence it will read very low when open circuit (infinitely high resistance) and very hot when short circuit (very low resistance).

I don't think the sensors are waterproof, so I wouldn't recommend dunking them. (Well not a working one)

I'm sure a few of them that I've changed over the years are down to coolant getting in/around the thermistor (I believe the metal disc is to transfer the heat). A couple have looked really crusty around that metal disc from corrosion.

It could be held against the side of a kettle with a multimeter attached then?

That would work, yes.

Pretty sure my heater core sensor is not good (so don't use this data as a reference), but after chucking the sensor in the freezer it reads about 700k ohms. At body temp it's about 230k ohms, over a kettle it's about 45k. On Nano it was reading about zero at rest, and 20 degrees or so when up and running, so definitely out of range. Anyone got real data from a working one?

I got a 20k NTC thermistor, arrived yesterday, plugged it in, and Nanocom reads more sensibly. It didn't do anything for the air con though... I'll get a replacement sensor and go from there. At least the weather is s*** these days so no need for air con, although on the plus side I got my sun roof working the other day (was turned off in the BECM...if only everything was that easy).