Red Transmission oil temp light on all the time. Need your help please Guys.

**wedgetail37** · 22nd April 2018, 09:01 AM

Hi guys

The red Transmission oil temp light is on all the time on my Discovery 1. Its obviously not a hot transmission as it is on as soon as |I start the Beast.
It is a 1998 auto 300tdi old mate.
I haven't a clue where to start to track down the problem. Has anybody had this problem before? and/or does anyone want to give me a place to start.
Does it have a fuse? I cant see one. is this a common fault etc etc. Any help would be appreciated.
If anyone can point me in the right direction to fix it, then I will turn all your Chooks into Emus and they will give you bloody big eggs for your Brekky. (or they might just kick your fence down. I am not sure hahahahahahaha.)
See ya - Gerry

**justinc** · 22nd April 2018, 09:16 AM

The d1 also has wiring underneath for a transfer case temp sender thst is not fitted on diesel models in Australia. The 2 wires can possibly rub through on the transmission case or similar, make a connection and set light off . There is also the more likely scenario thst the trans temp semsor which is attached to one of the cooler lines fron left of engine next to front crossmember Under radiator shroud has failed or the rubber boot is full of water.

**AK83** · 22nd April 2018, 10:09 AM

Mine is doing the same thing.
Due to my inherent laziness tho I'm still yet to fit the new switch I bought about a year ago!

Switch part no. is 8510043 .. do a google search on 'landrover 8510043' and it will come up with the part you need.
Not cheap tho!(~$80-$100)

Pull the plug off the switch that JC mentioned.
Easy from under the front, passengers side. You kind'a do it by feel as from underneath you can't see the actual switch as it's mounted on top of the pipe.
Hard to see from the top as it's deep down and lots of stuff in the way.
You need a 7/8ths(AF) spanner to remove the switch.

What mine does is that when I pull the plug and then replace it, the light goes out for a while but then comes back on eventually.
Sprayed the plug and switch contacts(2 of) with contact cleaner, and still the same issue.

Not sure if any trans oil will ooze out when the switch is removed tho .. but I'm about to find out, I guess!

**justinc** · 23rd April 2018, 05:47 PM

Originally Posted by AK83

Mine is doing the same thing.
Due to my inherent laziness tho I'm still yet to fit the new switch I bought about a year ago!

Switch part no. is 8510043 .. do a google search on 'landrover 8510043' and it will come up with the part you need.
Not cheap tho!(~$80-$100)

Pull the plug off the switch that JC mentioned.
Easy from under the front, passengers side. You kind'a do it by feel as from underneath you can't see the actual switch as it's mounted on top of the pipe.
Hard to see from the top as it's deep down and lots of stuff in the way.
You need a 7/8ths(AF) spanner to remove the switch.

What mine does is that when I pull the plug and then replace it, the light goes out for a while but then comes back on eventually.
Sprayed the plug and switch contacts(2 of) with contact cleaner, and still the same issue.

Not sure if any trans oil will ooze out when the switch is removed tho .. but I'm about to find out, I guess!

Yes trans oil will leak. Replace the copper washer with new unless you want a steady drip😣

**wedgetail37** · 23rd April 2018, 06:13 PM

Thank you guys. It gives me a place to start and hopefully this is the problem. Have a beaut Sunday. See Ya - Gerry

**AK83** · 23rd April 2018, 10:33 PM

Originally Posted by justinc

Yes trans oil will leak. ....

Yeah, finally got off my posterior on Sunday and changed mine.
Lost about 50ml of trans fluid, and I had the new one right there ready to go.

Couldn't find any specs on what resistance the switch should display when 'cold', but I measured my old one at 12-15 Mega Ohms .. which sounds like a lot to me.
Stupidly tho, I forgot to measure the new one before fitting.

**Old Farang** · 24th April 2018, 02:50 PM

Originally Posted by AK83

Yeah, finally got off my posterior on Sunday and changed mine.
Lost about 50ml of trans fluid, and I had the new one right there ready to go.
Couldn't find any specs on what resistance the switch should display when 'cold', but I measured my old one at 12-15 Mega Ohms .. which sounds like a lot to me.
Stupidly tho, I forgot to measure the new one before fitting.

I think that you will find that this is a simple on/off temperature switch (8510043/PRC8473/AMR4948), not a sensor that varies resistance with temperature.
Those cars that also have a TC sensor are wired to the same indicating lamp on the dash.

**wedgetail37** · 25th April 2018, 11:20 PM

Hi Guys

You wouldn't believe it. Whilst I was collecting and collating info from fellow Club members so I could tackle the problem, it fixed itself. I went out four wheeling on some rather rough coastal sand tracks today with my two sons and their Land Rovers. I got home and decided I wanted to have a few cans of Bourbon and Coke. I went to the local booze shop and for the first time in a couple of months the light was not on. We go four wheel reasonably often and I would like to think that a rough sandy track unplugged the AT temp switch and then a rough sandy track put the plug back on. I would like to think that, but I am not quite that stupid (not quite). So at the moment only the Gods know.

Thanks again to all of you and I will keep a close eye on it and inform you guys and this Forum as to what, if anything, might eventuate.

Have a beaut day - Gerry

**AK83** · 26th April 2018, 08:37 AM

Originally Posted by wedgetail37

Hi Guys

You wouldn't believe it. Whilst I was collecting and collating info from fellow Club members so I could tackle the problem, it fixed itself. I went out four wheeling on some rather rough coastal sand tracks today with my two sons and their Land Rovers. I got home and decided I wanted to have a few cans of Bourbon and Coke. I went to the local booze shop and for the first time in a couple of months the light was not on. We go four wheel reasonably often and I would like to think that a rough sandy track unplugged the AT temp switch and then a rough sandy track put the plug back on. I would like to think that, but I am not quite that stupid (not quite). So at the moment only the Gods know.

Thanks again to all of you and I will keep a close eye on it and inform you guys and this Forum as to what, if anything, might eventuate.

Have a beaut day - Gerry

Yep! they seem to do that ..... well, mine did a few times, and why I knew the temp sender unit was stuffed, and not the wiring.

Now that it's not always on, does it come on for 3 sec(and then off) when you first turn the ignition on? Similar to glow plug dash indicator, but not as long.
This is what they're supposed to do, and mine stopped doing that too.

After a short time seemingly working again, it then came back on(all the time) and then developed this weird habit of slowly going out at a specific engine rev point and throttle position.
Can't remember exactly, but as an example .. just under 80k/h with torque converter unlocked, I could hold the accelerator at a certain point holing (say) 1900RPM or so and it would fade out as it hit the revs sweet spot!

Strange thing is that it wouldn't then do the same if I was at 90 or so k/h torque converter locked and trying to do the same with with revs and accelerator!

It got weird in it's final days. Last few days before I replaced switch it stopped coming on at all.

Thread: Red Transmission oil temp light on all the time. Need your help please Guys.

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Red Transmission oil temp light on all the time. Need your help please Guys.

Thank you guys.

You wouldn't believe it.

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