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Defender Outside Thermometer - An Easy Install


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With the recent poor weather and my local authority's hit and miss policy of gritting the roads around where I live I decided to fit an outside thermometer to my TD5 Defender 90 XS to help judge how cold conditions are. In previous Defenders I have owned I have tried to do this a number of times, but the thermometer units I bought were really poor quality and inaccurate - I am sure you will have seen these advertised. I also wanted an easy install as my workshop roof is now laying in the next county due to the recent high winds.

After the bit of research I found a really good thermometer that is used by people who keep reptiles. You can find it on eBay at this link:

http://www.ebay.co.uk/itm/160772214729?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

The unit has an inside/outside functionality as well as relative humidity. It is battery operated (AAA) so no power wiring headaches, but best of all it only costs £9.99!

The install was really straight forward and only requires a little bit of fettling to prepare it for your Landy. The temperature probe does not have a very long wire attached to it, but a piece of speaker wire can be attached to ensure correct length (long enough to reach from your dash, down to the footwell and then under your Defender to the inside of the front wing). I tested my connections then soldered and heat shrunk the speaker wire into the circuit.

Next I decided the best location for the display unit. I decided to to mount it in the bottom righthand corner of my windscreen and fixed it in position with some double-sided foam sticky tape (you can buy a roll of this stuff off Amazon) - see attached pic.

I would recommend that you fix your probe in place first and fit the display unit at the end - it just saves you having to peal off and restick etc...

I then ran the probe wire down the side of the dash and then across to the drivers door seal. Because of the size of the wire it will fit inside of the door seal all the way down to the footwell - see attached pic.

In the footwell I ran the probe wire out and across to a pre-drilled drain hole - the probe just about fits so I would advise not adding anything to it until you get it in the final mounting position - see attached pic.

From here I ran the probe and wire forward to the inside of the front wing. The probe has to be away from the engine as the engine heat will effect the units reading. I toyed with the idea to position the probe under the drivers side, but thought that it would get caked in mud and therefore effect the accuracy of the readings. The final resting place was at the front of the wing away form the headlights - heat issues too. Where I could I zip tied the wire into place.

I now have a very simple and effective inside/outside temperature gauge in my Defender that is functioning beautifully. The only downside is that the display unit is not backlit so reading it at night is a little tricky. There are more elegant solutions that are more in keeping with the Defender dash, but these require a lot more work and come in around £70 - £80. If I had the time I would install one of these, but for now I am really happy with my immediate fix. The following link is to one of these more expensive units:

http://www.ebay.co.uk/itm/Check-Temp-Time-Internal-External-car-temperature-guage-vehicle-thermometer-/370647874159?pt=UK_In_Car_Technology&hash=item564c55ba6f

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Funny you should raise this as I've bought a cheap unit from Lidl to do exactly the same thing. Have not open the box yet, as it was less than £4 I thought I would give it a shot it's a fairly slim unit and comes with ice alarm, 3m cable and a clock. whilst displaying both internal and external temps together. not sure if it has a back light but also runs on batteries. I will try to power it via a suitable voltage dropper.

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Yes, very funny this is mentioned as I too have been tinkering with a temperature gauge too.

I started with the Lidl one, but that died! The problem with that one though (and others) is they're difficult to see at night. So I got myself a funky little one off eBay with lights - you can even select orange or blue back light!

It has three round displays (temp in, temp out and clock), fairly long probe lead and was about a tenner. It's designed to be plugged into the cigerette lighter when you want the back lights (the actual sensor runs off a battery), however I cut the cigerette lighter connector off and hardwired it to the back of my clock. So... when I turn my lights on at night, ta darrr I can see what the temperature is!

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Good idea about wiring it into your clock - did not think of that! I think I know the unit you are talking about and I have bought one, but I found that it was not the most accurate and fell apart pretty quickly. The unit I bought seems to be better made, but only time will tell.

Next thing I want to do is improve the heating in my Defender - I want to be about to heat the rear as well as the front so that I can see out the rear windows on cold days and not have them all misted up. Thinking cap on...

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Any probe NEAR the engine bay will get heat sink from the engine when stationary. I thought I was being clever having the outside probe bolted to the inside of the headlight box. I was wrong. The heat from the intercooler affects the probe when stationary. It's alright when driving.

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Good idea about wiring it into your clock - did not think of that! I think I know the unit you are talking about and I have bought one, but I found that it was not the most accurate and fell apart pretty quickly. The unit I bought seems to be better made, but only time will tell.

Next thing I want to do is improve the heating in my Defender - I want to be about to heat the rear as well as the front so that I can see out the rear windows on cold days and not have them all misted up. Thinking cap on...

Yes! Not the best made piece of tat from China! After installing it, and putting the battery in it would only work intermittently. I took the back off to find one leg on a capacitor leg had made snapped off, probably from movement of the high tech method the manufacturer used to stop the power lead being pulled out - a knot! Easily put right with my soldering iron though.

Also, when the lights are on, the inside temp slowly goes up to around 60 degrees! I'm thinking the power lead could be touching the inside temp sensor and any heat from that lead is responsible for the high temp reading.

And yeah no doubt it isn't very accurate but, I guess you learn what it reads when things get 'troublesome' out there. i.e when it read 6 degrees you know it near freezing! :hysterical:

As for your rear windows fogging up I dont think there's an easy solution. However do you purchase one of those 12v ceramic heaters! Been there, they're pants. Y fronts even.

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IF, note the IF.

If I do move the probe on mine I'll put it to the outside bottom of the headlight box.

At present it's in the headlight box but to the center of the vehicle. I know that the outside temperature reading will not be the actual outside temperature but as you drive you will see the temperature drop and settle to the correct temperature.

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OK, thanks. Will investigate this further since have been very taken with the value of the temperature indicator on my wife's wee car. Really rather useful at this time of year.

Better start looking to source one but like idea of back lighting the screen since by the nature of the beast you are more likely to hit interesting temperatures at night in winter!!

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The wouldn't be any difference outside to in with my 90 ;)

Interestingly enough I had an indicated 30 degrees whilst driving at night in the cold spell last March with the heater on full bore! Benefit of a V8 I suppose, if a little expensive way of being warm!

Interesting. Any consensus on where best place to try and mount the probe is??

I tried the inner wing, behind the headlight but found the temperature to rise as the engine warmed up. Probably the viscous fan chucking heat in that direction. I now have the sensor inside the O/S dumb iron - there's a handy little hole on the side! Like ballcock says anywhere in front of the radiator is ideal.

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off the back of everyone's comments, i have decided to locate the probe behind one of the outriggers under the driver's seat. this way it is away from any heat source, including the exhust, and i can give it a blast with the power hose once in a while to keep it free from gunk...

As for the back windows, i have them and it would be nice to use them - especially as i use my wagon as my daily drive :i-m_so_happy:

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As for the back windows, i have them and it would be nice to use them - especially as i use my wagon as my daily drive :i-m_so_happy:

I too use mine as a daily drive. It's the only vehicle that I have.

I suppose having learnt in something a little larger with only small exterior mirrors I've not used an interior mirror much.

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I used to have three thermometers very similar to this one:

http://www.ebay.co.uk/itm/Test-Temperature-Thermometer-Digital-Thermometer-Panel-PMTEMP1-/121194769825?pt=UK_Sound_Vision_Audio_Cable_Terminations&hash=item1c37c56da1

Except, supplied by Maplin.

One measured the engine block temperature, the second the water temp and the third the ambient temperature. The block and water should be about the same. If not, there is a problem with the cooling system - this made it much easier to spot!

The block temp was measured by using heat-sink glue (from RS) to stick the probe to the block.

The ambient was measured by drilling a hole in the heater plenum chamber in the wing just behind the vent so rainfall did not land directly on the sensor. It was largely unaffected by the engine or movement. It did heat up in hot weather as the whole vehicle was warmed by the sun, but read accurately as soon as the blower was running.

Si

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I have one which is switched with the rest of the instruments and operates off the vehicle battery.

I found the best location for the probe was level with the bottom of the front wing just in front of the OS wheel, is not affected by any heat sources and has proved perfectly reliable over the past 12-months.

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Fantastic idea! I always fancied a big mechanical pointer on the bonnet to show which direction the wheels were pointing - but a giant thermometer is even more useful!

Si

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