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Joined: Jul 12 2016
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If this fails would it show -20 degrees in Nanocom?

Mine is showing -20 degrees.

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Joined: Dec 30 2015
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Yes, it's open circuit.

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Joined: Jul 12 2016
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And, based on the name, I'm guessing it's in the side of the heater core in the depths of the dashboard?

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Joined: Dec 30 2015
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It's the one clipped to the inlet pipe next to where the O rings live. The clip can break so it falls off the pipe and just dangles so reads ambient temperature. I know it's been cold but I doubt it got that cold.......

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Joined: Jul 12 2016
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Sounds like an ideal candidate for when I replace my blower motors. Might as well pre-emptively do the o-rings while I'm there!

Going to be a busy year under/in the P38 this year!

Ball joints, heater stuff, suspension bushes...

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Joined: Jan 05 2016
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Bastard clip is a pain to get back on... it will probably snap when you do. If it does... cable tie.

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RutlandRover wrote:

Might as well pre-emptively do the o-rings while I'm there!

Well, that's no longer going to be a pre-emptive job. Found a nice pink damp patch on the side of the transmission tunnel this afternoon.

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Joined: Jun 16 2018
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Good luck with finding one. I've been looking for a new one for when I do my O-rings. Got to the point now where I've got one on order with Craddocks but they've no idea if and when it will arrive - most suppliers say it is an obsolete part! (STC3256 in case you're wondering)

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Well that's annoying. I looked earlier in the year and thought they were available. I saw £30ish, decided that wasn't so bad and I'd get one when I decided to do the work. I must have not paid enough attention to stock level info.

Have you tried an LR dealer?

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Joined: Jul 12 2016
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https://www.devon4x4.com/stc3256-sensor-heater-388961.html

They don't have anything to say it's not in stock or otherwise unavailable. Tried them?

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Joined: Jul 12 2016
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If this sensor fails and the system thinks the core is at -20 would it stop the AC coming on?

Now that it's getting warmer I've tried my AC and found it's not getting cold. It was regassed last year and held pressure and vacuum so I'm fairly confident it's not leaking. It's not impossible though.

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Not sure how it will affect the AC but mainly it means your fans won't come on. Normal operation is on a cold morning with the system set to Auto, the fans don't start up until there is heat in the matrix so it doesn't blast you with cold air when you really want hot air. After a cold start you should hear the fans ramp up in speed as the temperature increases.

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Interesting, my fans are working exactly as you describe and have done all winter. Slow/no fans on a cold morning then they kick in after a few minutes.

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Joined: Jun 16 2018
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Yep - phoned Devon - none in stock. Same for Island4x4 - they emailed to say that some S/H ones were available on ebay. Websites not telling the full story. I have an outstanding order with craddocks but not overly hopeful as I've now had 2 emails telling me that they don't know when they'll arrive........

Guess it is a case of grab em where you can. Question is, do they genuinely fail or do the clips just break off?

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Joined: Dec 29 2015
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I'd be terribly surprised if you couldn't find a suitable thermistor and make up a connector for it.

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Joined: Nov 16 2016
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gordonjcp wrote:

I'd be terribly surprised if you couldn't find a suitable thermistor and make up a connector for it.

Or just connect the wires.
Lots of different spec thermistors are used in the LPG conversion scene and are dirt cheap. I chuck loads on the floor and eventually sweep them into a bin - Lots of LPG ECUs come supplied with a thermistor that would normally be fitted to the reducer... if the reducer didn't come supplied already fitted with a built in thermistor. Could send as many 2.2k thermistors as you like or could easily get hold of other specs.

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Joined: Jul 12 2016
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I've just had a look through electrical troubleshooting manual but it doesn't seem to give them specs for the heater core temp sensor.

Anyone know what the specs are?

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Joined: Dec 30 2015
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I believe they are a 10K NTC thermistor for all of the P38 HEVAC Temp sensors

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Joined: Jan 07 2016
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Hey Marty,
Good to know it is NTC......I have a bag of 10k PTC parts here (10k @25c) and was going to try one on the Borrego........Nano says temp sensor is bad, but HVAC works fine?
Do you know if the outside temp sensor is same?

For those not Geekier enuf' NTC is Negative Temperature Coefficient. PTC is Positive. Means resistance falls or rises with temp change.
Thermistors cost about 5 of whatever currency you want to use....Cheap as Chips!

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Joined: Jul 12 2016
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Following a bit of a mishap with the replacement of my heater o rings my sensor was disturbed.

It now seems to be working! Not sure why but current thinking is either a loose connection or some coolant contact from the o rings.

Might be worth giving the electrical connector a wiggle before assuming the sensor is dead.