Water Temp gauge not working ?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Nov 20, 2011
Threads
51
Messages
250
Location
USA
Hi, 1981 Toyota FJ40, recently the engines water temp gauge in the dash cluster just stopped working, nothing, not even a flinch.
Was working fine but the cluster was removed to install new dash light bulbs (brighter one's) and after that reinstalled the dash cluster and nothing. The cluster was never dropped or smacked . Checked the wires to make sure nothing was crushed or broken. The black round main plug looks okay and the prong plug looks good also. That's all that's on the back that I can find. All the other items in the cluster work fine - turns signals, oil temp, lights, the amp never worked. Checked the wire at the sensor and it looks in good condition and connected.
Were should I check next? Thanks nuch.
 
Sounds like you're going to be pulling the cluster back out.
I'd start with grounding the wire to the gauge, using the temp sensor as that's easiest. Gauge should go to hot, don't leave it there. If that moves it, it's time to test the sensor.
If gauge didn't move, then move onto testing continuity of the wire. I have a cheap tone generator I used to use testing CATV wiring and like the chance to use an otherwise unused tool. I also find it easier to trace wires in and out of looms.

I'm not familiar with what happens once it's at the cluster. Wish you were closer, I'd like to learn more about it.
Good luck, hope it's an easy fix.
 
I gave grounding it a try but got nothing, ran a wire from the pin on the back and direct to the sender. nothing"

Looks like this one in the picture I found on the web. Thanks
1953062
 
I know you mentioned that it was working before the initial removal. With that being said, I’d check the thermostat housing with an inferred thermometer. Just to double check that the engine is getting up to temp.
 
Instead of grounding the temp sensor and using the gauge deflection as a determination, ground the sensor and use a voltmeter to see changing. It could be the gauge itself.
 
I gave grounding it a try but got nothing, ran a wire from the pin on the back and direct to the sender. nothing"

Looks like this one in the picture I found on the web. ThanksView attachment 1953062


Hi Leo,

please elaborate how u ran a wire from the sender unit on the cylinder head to the Pin on back of the cluster ?

was the black Barrel connector also connected & plugged in at the same time or disconnected during this Field Test

if it was plugged in how did u connect the test wire to the Temp. Gauge male Pin on the cluster

if your black barrel was disconnected during the use of the test wire to the sender gauge then that may help explain some

things too


i know grounds were discussed above , but did u take a aligater clip and hook to a phillps head screw back side of cluster ,

then a known good ground on your dash somewhere


lastly , please verify u are focused on the Yellow wire w / the green tracer stripe , if not what color code wire are u working with

on this temp. gauge issue ?

if u noticed the black barrel connector is Numbered 1 - 12 let me know what # terminal Bay u are working with


I posted photos of My white Barrel connector kit so u have a Navigation Aid and Cross Comparison to study and work with



thanks



1953685



1953686



1953687


1953688


1953689
 
Okay a lot of questions so I will try to answer them as best as possible.

Sounds like you're going to be pulling the cluster back out.
I'd start with grounding the wire to the gauge, using the temp sensor as that's easiest. Gauge should go to hot, don't leave it there. If that moves it, it's time to test the sensor.
If gauge didn't move, then move onto testing continuity of the wire. I have a cheap tone generator I used to use testing CATV wiring and like the chance to use an otherwise unused tool. I also find it easier to trace wires in and out of looms.

Checked the sensor by the book for Oms and it passed as the book shows.
Grounded the senor wire while power was on and nothing moved.
Tested the senor wire as best as possible as I only have a test light but with power on we get not conformation of power.
Thanks

The battery was not disconnected before removing the cluster.

I did check the thermostat with a inferred thermometer and it shows normal warm up to proper temp as the manual says.
[U]RAGINGMATT[/U]
Did not run a wire from the plug in pin only to the ground is what I meant.
The plug in was connected and disconnected for the tests
I used the door bolt for the ground point, no Philips head on the back of the cluster.
I believe the wire color is yellow. I can check again.


I have a feeling that the gauge just gave up and failed being 30 something years old and never the cluster never being removed
before. I guess its pretty basic wiring and the only delicate item in the system is the gauge. I never bumped it but and I never dropped it?


Thanks
 
I wanted to ask - is the suppose to be power going from the wire to the sensor on the head or is it just a ground. I did try to see if it has power with my test light unless its really low MA type.
I think just for the heck of it to put in a new sender.
Also there are two what look to be sensors with small rubber tubes ruining up to somewhere on the top of the engine. The two sensors are located at the base area of the thermostat housing.
 
Last edited:
No power. The sender lowers resistance as it gets hotter. If you think it might be the sender, pull it out, measure the resistance on it. Place it in a cup of hot water for a minute or two and remeasure the resistance.

Unfortunately I don't think it's the sender, since when you grounded it, the gauge didn't move.
 
I think your right, I did the check with the meter as noted with the manual and it passed so yeah maybe the 38 year old 40 needs some attention.
I will post what happens with a new gauge. I will try the ground one more time at the back of the black pin plug with power on and see if it deflects, got to pull out the gauge anyway. Thanks guys.
 

Users who are viewing this thread

Back
Top Bottom