Coolant temp guage

[stericker]

It has been a long time since I last posted. Moved from London to Tunbridge Wells three years ago. Only LS 400 in town so easily recognised (sometimes too easily !)

The temperature guage on my LS 400 (1999) 156K miles has just started to play around. It fails to rise initially and then from time to time, during a journey,

will flick on and show the expected temp.and then go back to zero again. Should I be worried ?  Could it be the thermostat ? Your advice please.

[Tinonline]

Hi. I doubt there’d be such an erratic rise in the case of a thermostat. The gauge shows over cool or worse case too high. That leaves the sender unit itself (cheaper fix and test) or the gauge. 

[Razor61]

Could be thermostat but I don’t think so. I would guess at the temp gauge itself, mine went a month or so ago.
Temp gauge went higher than normal so had it checked out at Lexus in case something was about to go pop. Main concern was head gasket/s.
Nothing was wrong and it was the gauge itself, I slapped the dash on the right hand side and the gauge was all over the place.
I bought a spare instrument cluster a while ago and swopped the main board from the existing cluster to the spare one. Fitted it and all is good.

[Howplum]

Or it could be a component on the circuit board. Apparently faulty electrolytic capacitors can cause the gauges to become erratic.

[Malc]

12 hours ago, Howplum said:

Apparently faulty electrolytic capacitors can cause the gauges to become erratic.

Wot .............     Fawlty after 23 years, c'mon  it's a Ls400 ....... NEVER .....  well, not until geriatrics take hold after the age of 25 surely 

Then a good slap often wakes it up into action as you say

Us owners are living in a time warp with our aged limos ........  all these strange experiences will never be known to the to younger car ..... owners ....  coz they never get to this age 

Reading summat " Official " yesterday that the general scrappage age is now at about age 13 

Mine's 100% uplift in Green Credentials then being now only aged 27 

Malc

[BigBoomer]

Temp gauge or Temp sensor is crapping out.
Will not be the thermostat.

[stericker]

Thank you all for your responses. Might start by giving it a bit of a slap above the dash. Always works when the speedo gets stuck.

Will keep you informed.

[Razor61]

21 hours ago, stericker said:

Might start by giving it a bit of a slap above the dash.

That won’t fix it like the speedo, if it is the actual gauge that’s faulty. I did it to prove it was the gauge at fault and not anything more serious. With mine it sometimes stayed at the bottom on cold, slapped the dash and it moved up a bit, another slap moved it up a bit more.

[Tinonline]

On 9/9/2022 at 8:59 AM, BigBoomer said:

Temp gauge or Temp sensor is crapping out.
Will not be the thermostat.

Yup I’d start here as it’s a relatively quick replacement and worth doing anyway.

[stericker]

I went away on holiday shorly after my posts on the coolant guage. As always I diconnected the Battery.

On return. and after reconnecting the Battery, the guage is acting normally. Battery disconnection seems to solve a number of problems.

I now am being told by my better half that the car is too big and we need something smaller. I shall try to sell it on the forum as I am a gold member.

[Tinonline]

1 hour ago, stericker said:

I went away on holiday shorly after my posts on the coolant guage. As always I diconnected the battery.

On return. and after reconnecting the battery, the guage is acting normally. Battery disconnection seems to solve a number of problems.

I now am being told by my better half that the car is too big and we need something smaller. I shall try to sell it on the forum as I am a gold member.

Great idea and keep the car. 😂

[Malc1]

1 hour ago, stericker said:

I now am being told by my better half that the car is too big and we need something smaller.

she's totally NUTS  ...........  smaller, newer and much bigger bills and far less comfort and reliability no doubt about it 

You'll regret forever and a day trading down away from your Ls400

Malc