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Hi

I was driving along merrily in my Jan 1995 MK3 LS400 when suddenly no temperature gauge reading. Stopped to investigate, nothing obvious ie wires, boiling-over etc so continued a further 30 miles or so with no adverse issues. Infact she was running as well as ever. There are no warning lights illuminated.

After searching this forum, Googling and running my Mitchell repair disc, I am non the wiser as to why the gauge has died or where the sender is located. Any assistance will be gratefully received.

Steve

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Have a look at this:

http://i24.photobucket.com/albums/c45/buck.../tempsender.jpg

Should be the same as yours.

Hi

I was driving along merrily in my Jan 1995 MK3 LS400 when suddenly no temperature gauge reading. Stopped to investigate, nothing obvious ie wires, boiling-over etc so continued a further 30 miles or so with no adverse issues. Infact she was running as well as ever. There are no warning lights illuminated.

After searching this forum, Googling and running my Mitchell repair disc, I am non the wiser as to why the gauge has died or where the sender is located. Any assistance will be gratefully received.

Steve

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Have a look at this:

http://i24.photobucket.com/albums/c45/buck.../tempsender.jpg

Should be the same as yours.

Thanks for that Steve, and a local reply to boot (me being in Sleaford).

I will have a look in the morning to compare, although I'm not that confident having searched high and low today. Will report back

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The sender unit should be located on top of the intake manifold below the IAC valve,the wiring to it should be yellow/green.

If you have no gauge reading it is normally due to an open circuit ( wire off or broken) so check at the sender unit 1st ( if the gauge reads hot all the time it is normally a short in the wiring to earth).

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I would have a sniff around your local Motor Factors/Lexus main dealers etc, anywhere you could get one from and price them up.

Japparts have them at 15 quid:

http://www.japarts.co.uk/shop/

Its under the Electrics/sensors menu for the LS, all the years have the same part number (J5622003) so its common to all 400`s by the looks of it.

Cant see any on E-Bay, but at least you have got somewhere to get one from, if you cant source one locally.

BTW before you order, just give them a call to ask them if this is the right part.

Steve, Steve

Unit located so thanks. Shorted the wiring and gauge shot up indicating defunct unit. So going to have to source a new one.

Steve

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I would have a sniff around your local Motor Factors/Lexus main dealers etc, anywhere you could get one from and price them up.

Japparts have them at 15 quid:

http://www.japarts.co.uk/shop/

Hi and thanks once again.

Sourced from local factors at £10.84 inc VAT. Should be in tomorrow.

Given the location on the inlet manifold, I'm hoping to do the job with minimal coolant loss.

Steve

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Hi Guys

The plot thickens. After I shorted the wiring the other day, the gauge has been reading half way between off and a "quarter" when warm. Anyway, changed the sender unit today and............, the gauge still reads half way between off and a quarter! Shorted it again, same result - gauge shoots to max. Much head scratching and no inspiration.

Any ideas as to whats happening fellas? cant believe that the new sender has exactly the same problem as the original.

Steve

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Try getting a jump lead, putting one end on the Battery negative terminal and the other on a none painted clean engine part, see if the guage works properly.

Hi Guys

The plot thickens. After I shorted the wiring the other day, the gauge has been reading half way between off and a "quarter" when warm. Anyway, changed the sender unit today and............, the gauge still reads half way between off and a quarter! Shorted it again, same result - gauge shoots to max. Much head scratching and no inspiration.

Any ideas as to whats happening fellas? cant believe that the new sender has exactly the same problem as the original.

Steve

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Odd.

It could be a faulty sender that they supplied you.

Is your fuel gauge working ok?

when you replaced the sender, did water come out of the hole?

And (no insult intended, it happens) are you sure you didnt put the old one back in instead of the new one?

Try getting a jump lead, putting one end on the battery negative terminal and the other on a none painted clean engine part, see if the guage works properly.

Made no difference to the reading

Steve

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Odd.

It could be a faulty sender that they supplied you.

Is your fuel gauge working ok?

when you replaced the sender, did water come out of the hole?

And (no insult intended, it happens) are you sure you didnt put the old one back in instead of the new one?

Try getting a jump lead, putting one end on the battery negative terminal and the other on a none painted clean engine part, see if the guage works properly.

Made no difference to the reading

Steve

Water did come out of the hole and it was the new one that was fitted; I have the old one in view.

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And the fuel gauge reads normal? if not then it could well be a dash fault.

There is another Temperature sensor, which I believe is the green plug on that photo, but I think that one is to do with the engine ECU and not the gauge, and I think you would get a management light come on if that was faulty.

If you have a multimeter, you can test the sensor set to read ohms.

the procedure is here:

http://www.topbuzz.co.uk/maintenance/cts/cts.htm

That is for a Vauxhall, so although the procedure would be the same, the readouts probably would not be.

You could test the new one on the car, and the old one in a pan to see how the two compare.

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  • 2 weeks later...
And the fuel gauge reads normal? if not then it could well be a dash fault.

There is another Temperature sensor, which I believe is the green plug on that photo, but I think that one is to do with the engine ECU and not the gauge, and I think you would get a management light come on if that was faulty.

If you have a multimeter, you can test the sensor set to read ohms.

the procedure is here:

http://www.topbuzz.co.uk/maintenance/cts/cts.htm

That is for a Vauxhall, so although the procedure would be the same, the readouts probably would not be.

You could test the new one on the car, and the old one in a pan to see how the two compare.

Hi again

Ive now tried everything including every electrical device except heated rear window and heated seats. Everything works fine. I have no dash lights lit or out (except the D light which has never worked and I will change if and when the dash comes out).

I have also tried to overfill the coolant to rule out an air lock. No change.

I have now ordered an original replacement temp gauge sensor as being the only thing left I can think of :shutit:

Steve

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  • 3 months later...
And the fuel gauge reads normal? if not then it could well be a dash fault.

There is another Temperature sensor, which I believe is the green plug on that photo, but I think that one is to do with the engine ECU and not the gauge, and I think you would get a management light come on if that was faulty.

If you have a multimeter, you can test the sensor set to read ohms.

the procedure is here:

http://www.topbuzz.co.uk/maintenance/cts/cts.htm

That is for a Vauxhall, so although the procedure would be the same, the readouts probably would not be.

You could test the new one on the car, and the old one in a pan to see how the two compare.

Hi again

Ive now tried everything including every electrical device except heated rear window and heated seats. Everything works fine. I have no dash lights lit or out (except the D light which has never worked and I will change if and when the dash comes out).

I have also tried to overfill the coolant to rule out an air lock. No change.

I have now ordered an original replacement temp gauge sensor as being the only thing left I can think of :shutit:

Steve

Hi again

Now, 4 temparature gauge sender units later including a very expensive one! (Least said soonest mended) I now have a complete car. Despite my protestations, it was infact the plug fitting and not the sender. By crimping the plug contact, I now have a a normal reading :shifty:

O Joy

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  • 2 months later...

Hi again.

Spoke too soon. Crimping-up the plug did work for a short while but alas its beyond the Heath Robinson approach.

Since my previous post on this subject, Ive moved house and installed a new kitchen and bathroom (in the house) and had serious issues with my daughter's Vauxhall Ashtray which has a wonderful Isuzu 1.7Td engine which eats alternators. Still I digress.

I obviously need a new plug with some wire for my baby's temp sender unit.

I have emailed the breakers on Fleabay without success. I have ALSO asked 2 Lexus dealers to supply the part. I have given them VIN and Engine numbers without success: they can only find a unit that has both positive and earth wires. Mine has a positive; it being earthed to the head. (Rant coming)

I am not a great fan of dealers notwithstanding prices. By way of example ( and if I thought about it, no doubt I could go on)

1) New Escort, 1st service. Walk in at 5.30pm man says "ah, should have rung you". Car has no engine, went home on bus.

2) New Terrano 5k service- new clutch. Gearbox fell off on beach 3 days later in south of France due to lack of 1 (ONE) bolt!!!! (Proven by nice man in France).

3) LS400. Ring dealer for paint touch-up colour - gave em code, "sorry sir, you will have to bring it in"

Rant over, I hope.

I need a plug for the temperature gauge sender unit for my LS400 1st registered 26/01/95 on Park Lane, together with say 4 to 6 inches of cable OR a reliable and p..s easy modification. If anyone can help, please.

By-the-way, I have a Mitchell manual on disc which leaves a lot to be desired especially the wiring diagrams.

StevewithoutatemperaturegaugeLS400

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Hi again.

Spoke too soon. Crimping-up the plug did work for a short while but alas its beyond the Heath Robinson approach.

Since my previous post on this subject, Ive moved house and installed a new kitchen and bathroom (in the house) and had serious issues with my daughter's Vauxhall Ashtray which has a wonderful Isuzu 1.7Td engine which eats alternators. Still I digress.

I obviously need a new plug with some wire for my baby's temp sender unit.

I have emailed the breakers on Fleabay without success. I have ALSO asked 2 Lexus dealers to supply the part. I have given them VIN and Engine numbers without success: they can only find a unit that has both positive and earth wires. Mine has a positive; it being earthed to the head. (Rant coming)

I am not a great fan of dealers notwithstanding prices. By way of example ( and if I thought about it, no doubt I could go on)

1) New Escort, 1st service. Walk in at 5.30pm man says "ah, should have rung you". Car has no engine, went home on bus.

2) New Terrano 5k service- new clutch. Gearbox fell off on beach 3 days later in south of France due to lack of 1 (ONE) bolt!!!! (Proven by nice man in France).

3) LS400. Ring dealer for paint touch-up colour - gave em code, "sorry sir, you will have to bring it in"

Rant over, I hope.

I need a plug for the temperature gauge sender unit for my LS400 1st registered 26/01/95 on Park Lane, together with say 4 to 6 inches of cable OR a reliable and p..s easy modification. If anyone can help, please.

By-the-way, I have a Mitchell manual on disc which leaves a lot to be desired especially the wiring diagrams.

StevewithoutatemperaturegaugeLS400

Hi Steve

I have some senders somewhere and I have a loom off a mk2 which may be of help as it is still a 1uzfe

I will have a look and check the wire compatability [ should be same]

and you can have the sender, plug and a cut of wire gratis

just pm me your address to post to

All The best

Maurice

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Hi Steve

I have some senders somewhere and I have a loom off a mk2 which may be of help as it is still a 1uzfe

I will have a look and check the wire compatability [ should be same]

and you can have the sender, plug and a cut of wire gratis

just pm me your address to post to

All The best

Maurice

Hi

Thats extremely kind of you. Have pm'd you

Steve

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  • 2 weeks later...

Stardate, sorry update.

We have now fitted the replacement sender unit. The connection was not the same as the original so the wiring has had to undergo a slight modification to accomodate. There is no question that the wiring is satisfactory following extensive testing.

In addition, before fitting, the resistance of the replacement was tested against the original sender and found to be in the same ball park. However, normal used to be "half" way on the temp gauge. The gauge now appears to function correctly, ie gradually rising, but it now sits on "quarter". Prior to this issue, no matter what the ambient air temp, the gauge would read half within a short time of starting out. Is the new normal now a quarter? Should I just live with it? Is it connected to my other post about the heater?

The gauge still shoots to the top when the wiring is shorted, but is there a resistor actually in the dash which could be accounting for the quarter reading?

Any new views very much welcome.

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Is the engine thermostat stuck open allowing the engine to run cool?

Hi again and ta for responding.

Given the findings today as mentioned in my Heater post as well as here I do wonder. I still cant accept that they are linked because the heater issue started in 2007 and the temp gauge in 2009. However, thinking out load...

The aircon was s..t in Le mans in June 2007, thus prompting me to have it sorted shortly afterwards. But I wouldnt have used the heat aspect of the system till end Sept 2007 or even later as it was then set on auto all the time and with the weather warm I probably didnt want mega heat until later on like Nov 2007. However the system did make groaning noises from earlier than that. So maybe the heater issue started AFTER the aircon refurb, I just didnt know. But.....

Why did the temp gauge wait until Sept 2009 to die? And ..........

Steve

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  • 1 month later...

Hi

I was driving along merrily in my Jan 1995 MK3 LS400 when suddenly no temperature gauge reading. Stopped to investigate, nothing obvious ie wires, boiling-over etc so continued a further 30 miles or so with no adverse issues. Infact she was running as well as ever. There are no warning lights illuminated.

After searching this forum, Googling and running my Mitchell repair disc, I am non the wiser as to why the gauge has died or where the sender is located. Any assistance will be gratefully received.

Steve

wow, sounds a right can of worms

after you buying stuff and the fault is still there suggests its similar to the mk2 dash syndrome. This boiled down to 3 capacitors at fault and i after realising i couldnt solder the tiny circuits then i sent it off to be fixed. When it came back my fuel gauge suddenly didnt work...well, at first. It seems to take 10 - 15 mins to read correctly when you 1st drive it. Occasionally after several stops it might read right straight away but more than often it takes ages. Unfortunately i didnt bother to inform the guy as the car had been stood for a while since re-fitting and time had gone by.. my own fault i know

you could do with finding chrisvince on here, he's the expert with mk2 dash only, but he might now have moved on a generation, you never know

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