Temp Gauge Weirdness 85 4runner SR5

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Racehoss

Racehoss

10 Year
Joined
Mar 24, 2011
Threads
26
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207
Location
Austin, Texas
Temp gauge goes immediately to the middle when the key is turned on. It doesn't move from the middle position if the engine is cold or warmed up. I've replace the Temp sending unit. If I tap on the gauge cluster the temp gauge sometimes moves to the cold side and then will come back up to the middle. Is it the gauge itself? Where can I get just a replacement temp gauge if that's the case. Thanks, Carter
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I've got a buddy sending me an extra temp and oil gauge. I'll see if that works.
 
Ya it's priority one right now because I don't think it's telling anything about the temperature at all.
 
What if you unhooked it from the sending unit...... when you turn the key on shouldn't the gauge be all the way pegged one way or the other? Might be worth a try to verify if it is the sending unit
 
right thats my thought but if you unhook the sender and turn the key on and it goes back up to half we should have ruled one item out..... I am not sure if it works off of ground or voltage as if it was based off of ground I would say ground the plug and see if the guage maxes out.
 
I don't think you want to ground out the gauge, it may fry it... Kind of like the oil pressure switch when you swap to an SR5 dash... If you unplug it and turn the key on and the gauge does come up, then I'd say that the sender is not the issue....

+12V goes to the gauge, then to the sender which provides the ground to the circuit....
 
Same issue here!!!
Very rarely, it will go down and work for a moment and begin to creep up like it should and then all of a sudden, it jumps back up to half way.

I hate it! I wish there was a fix for it.....

PLEASE, SOMEONE!!!!
 
Mine does the exact same as Gas-a-lot. Pretty much wants to stay in the middle but sometimes creeps up and then flips to the middle and stays there. I put a new sending unit in and same issue. Must be the gauge but how do you confirm that the gauge has issues and not the wiring or something else?
 
Already replaced the sender. Same issue
 
hilux508402-10-2007, 01:28 PM
I have just made a very interesting discovery about the way Toyota temperature gauges work.
I have always thought that Toyota cooling systems were rock steady reached operating temp quickly and no matter the days temp stayed steady in the middle.

I had reason to test a Toyota Coaster temp gauge and since checked 3 other Toyota's with the same result, the gauge move rapidly from cold to 75 then doesn't move between 75 and 98 degrees C then rapidly again at 99 it is almost in the red.

There is nothing wrong with this as it is in the normal operating range I just haven't seen it before, an interesting way of stopping all those customer complaints like it runs a bit hot or cold.

Joe

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johnv02-11-2007, 07:30 AM
My Temp. gauge operates exactly like you have stated also,and I also thought like you said once the operating temp. is reached it stays rock solid there without any variations which seemed a little strange to me there was never any changes to the gauge in extremely hot or cold weather just thought that the cooling system was functioning extremely effecient (like toyota qaulity?).
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This is some stuff I found while searching that doesnt help squat but maybe explains why it seems as though everything is fine and then all of a sudden you look down and go :eek:
 
Maintaining the right level of oil is important for a car engine so that you avoid damaging the engine. Many vehicles are equipped with a gauge that lets the driver know whether the engine is working within its temperature range. But it is hard to tell when the gauge needle stops working entirely and gets stuck at a Hot or Cold reading or wanders from one end to the other. Fortunately, gauges are one of those car electrical instruments easy to diagnose. You only need minimal knowledge of electricity to be able to determine in a matter of minutes whether the gauge in your vehicle needs replacement.

Difficulty: Moderately Easy Instructions
things you'll need:
1 to 2 foot-long jumper wire

Voltmeter


1
Unplug the temperature gauge wire at the sending unit, most likely located on the engine.

2
Turn the ignition key to the on position but don’t start the engine.

3
Ground the temperature gauge wire to the engine using a jumper wire, then watch the temperature gauge needle. If the gauge now reads Hot, replace the temperature sending unit. Otherwise, go to the next step.

4
Check the fuse for the temperature gauge circuit. If the fuse is good, go to the next step.

5
Unplug the temperature gauge wire at the sending unit and ground the wire using a jumper wire. Turn the ignition key to the "on" position. Using a voltmeter, check for voltage at the ignition terminal on the gauge. If there is no voltage, there is a problem in the circuit between the ignition key and the gauge or the fuse panel and the gauge temperature. Fix the problem and test again. If there is voltage, replace the gauge.

6
Connect a jumper wire to the sending unit terminal at the gauge to a good ground. Turn the ignition key to the "on" position. If the gauge now reads Hot, there is an open at the wire going to the sending unit. Repair and test again.

7
Take a close look at the gauge after you disconnect the wire at the sending unit and turn the ignition to the "on" position. If the needle at the gauge goes a little bit higher than cold range, go to the next step.

8
Unplug the wire going to the sending unit at the gauge. Turn the ignition key to the "on" position. If the gauge still reads higher than cold, replace the gauge. If the gauge now reads Cold, there is a short in the wire going to the sending unit. Fix the short and test again.



Read more: How to Troubleshoot a Car Engine Temperature Gauge | eHow.com How to Troubleshoot a Car Engine Temperature Gauge | eHow.com
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Check out step three that is how I remember testing them in the past but I am not trying to fry someones guage..... Therefor I volunteer to be the pig.... I would have to throw my battery back in and find the wire but if someone wants to remind me what wire I would be happy to ground my gauge. I have mechanical guages that I go by and do not hook mine up. The main question here is for those of you that are stuck half way when you unhook the wire does the gauge go to cold?? Mine is unhooked and it is on cold :meh:
How to Troubleshoot a Car Engine Temperature Gauge | eHow.com
 
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If you get a second while working on your TPS I would be curious about if you unplugged the sending unit and turned the key on would it still go to half way? That should completely take one equation back out of the mix and allow us all to search for where these things are wanting to short out at. I understand being busy though

Here is another yota thread that talks about grounding the single wire.... this is a good bit of info as to not accidently ground the two wire that 2ndgen may have been thinking of....:meh:

Temp gauge not working - Toyota Nation Forum : Toyota Car and Truck Forums
 
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Just cause the internet says it's ok doesn't mean it is... The bottom line is I know that if you ground the wire going to the oil pressure gauge, you'll be shopping for a new gauge. Maybe the temp gauge is different, but I would trouble shoot it properly. Get an ohm meter and test the resistance of the sender as it heats up.

And a quick check of the FSM says that you should ground the gauge through a 3.4 watt bulb (IE not directly to round) to check proper function of the gauge.

(The oil pressure gauge has the same test, so if you ground your temp gauge you can destroy it would be my bet...)
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Sender resistance:

while cold (60F) 146 ohms +26 ohms/-4 ohms
Whild hot: 115 24 ohms +1.3 ohms/ - 1.8 ohms
 
which is exactly why I stated that incase I am wrong I would be happy to ground mine first. If you recall I first stated I had done it before and later found it several times on the net resulting in me bringing it back up as a possiblility and offering to ruin my own stuff :meh: I am just pointing out that I am not a read it on the internet it must be true type person. And I made sure to post links to all my findings to allow others to verify for themselves prior to taking my assumptions that again are based on my recollection of what worked for me. I am certain if I had grounded it and held it there for several minutes yah I probably would have toasted it

2ndgen I understand your concern and I am simply seeing a reoccuring issue that has a bunch of people scratching their heads that I am willing to be the test rat on.......
 
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Hehe, I'm not ragging on you at all, I just want the proper test procedures followed first... If you ground a gauge, it might put up with it once or twice, or for 5 or 10 seconds, I don't know. But don't do it when there are other options available. I didn't feel like retyping the gauge tests, but they are in the Body Electric section of the FSM, all simple ohm tests that anyone can do with a $5 meter. :cheers:
 
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