xLowNSlowx

Hey guys, so i've got a 96 ls400 here and i'm wondering whether the water temp gauge on my cluster has gone bad.

When i start the car, temp needle would climb to the halfway point within 30 seconds. (highly doubt it's at operating temps)

If i have my AC on, after several miles of driving it would slowly...i mean very slowly continue climbing until it hits the 4/5 mark (white line before the red).

With AC off (only fan on), i've sat in stop and go traffic for 20 minutes and that needle did not rise.

Anyone ever have this problem before?

Background story:
temp needle always rose to tip-top when i first got the car, but my mechanic ran the car and tested water temps with the laser gun and said it was all fine, but the needle was just wack. Then one day, when i was driving with needle at the tip-top as always, smoke poured out from under hood and into cabin etc. after i towed to shop, turns out the heater valve was clogged and a water hose popped off from it spewing coolant everywhere. After repairing that valve, needle began to sit at the half-way point while running normally, unless i have my AC on...from here on refer to first half of post.


If anyone took their time to read through all that, i sincerely thank you and any ideas or help is greatly appreciated!

Shmee

iTrader: (3)

What year? Mileage?
Have you replaced, or were any of the following replaced, recently:
Water pump?
Rad ?
Thermostat ?
Temp sensor for ECU ?
Temp sender for gauge ?

johnnyg66

Most likely is the gauge. Seems to be a lot of this on the forum these days.

Mine went to half way point one day and never went back unless i pounded on the dash even then it only went half way down.

I changed the the thermostat first than changed the temp sender. When none of that worked i measured the resistance of sender at different times to see if the ohms matched what the engine temp should be. All seemed well so than i had to measure the resistance at the gauge that proved to be bad. Bought new gauge and for the past couple weeks now all is good.

xLowNSlowx

thx for the fast responses!

I believe the thermostat has been replaced as well as the temp sensor. Not sure about the temp sending unit to gauge.

Would an easier solution be to just get an aftermarket gauge installed to monitor temps?

Shmee

iTrader: (3)

If by easier you mean a method which requires zero diagnostic work then, yes, probably...
Not sure where you are going to mount your temp gauge or what gauge you could buy that would look good in the interior of your LS though.

Don't get me wrong, I'm all for the accuracy of an aftermarket gauge over the standard idiot-dial supplied in most cars that gives you the the stunningly accurate info that your temp is between "here and here." But the LS doesn't seem like a good fit for an aftermarket gauge IMHO....

TaninAuto

Common issue with the gauge cluster. We have all parts in stock to fix all LS clusters and climate units.

Shmee

iTrader: (3)

For the record, you should check the sending unit to the gauge. The temp sensor is for the ECU and does not cross over with the dash gauge at all.

TaninAuto

The gauge cluster temp signal should be the single wire on the t-stat housing. Disconnect it and the gauge should read "C" at all times.

If it reads anything higher than C, the gauge in the cluster needs to be replaced.

xLowNSlowx

Yeah, that's the downside, the gauge would look way out of place in an LS interior. totally agree with you.

xLowNSlowx

Got it, i'll give that a try to see if my cluster has gone bad.

I'll change that temp sending sensor as well, its $15 at autozone, worth a shot.

LScowboyLS

I would recommend replacing the gauge sending unit with the factory Toyota sending unit, it is cheap (around $20 online) and it was the problem on my 96, the actual gauge tends to not go bad on this year model.

also the wiring & connector right there at the sending unit can go bad, my Toyota fancy connector went bad and now it is just a regular spade lug!

do not confuse the gauge sending unit (one wire) with the Engine Coolant Temperature Sensor (ECTS) that has two wire prongs and sits right beside the gauge sending unit (one wire prong) - the ECTS supplies the ECU with temp information, but has no relationship with the dash gauge.

you can test your cluster gauge from the sending unit, by disconnecting it and also checking it's factory resistance range by grounding it through a 3.4W test lamp as per page BE-89 in the service manual