failing temp sender? how to test?

[marin]

How do i test the temp sender on my GQ? How many ohms should it be from the terminal to ground when cold? The manual says to take it out and put in temp controlled water and get a resistance reading, but i would prefer not to take out unless buggered. I am wondering because the temp gauge doesn't seem to go above about 1/5 even when i had a radiator full of mud.

[GQAndrew]

How do i test the temp sender on my GQ? How many ohms should it be from the terminal to ground when cold? The manual says to take it out and put in temp controlled water and get a resistance reading, but i would prefer not to take out unless buggered. I am wondering because the temp gauge doesn't seem to go above about 1/5 even when i had a radiator full of mud.

In my gregorys manual, there is no test for the temp sender, only the Coolant Temp Sensor, which controls Glow Plugs, not gauge. I had this exact problem though and assumed it was the temp sender, so bought a new one from Nissan, $58, no change in readings. Found out the thermostat was never closing off properly.
If you do find a way to test the gauge sender, let me know as I would also like to know this for future reference. Taking it out is not a problem, you just lose a tiny bit of coolant, so after you unscrew it, just put something over the hole to minimise it.

[marin]

Nissan manual says:

Thermal Transmitter Check

Check the resistance between the terminals of the thermal transmitter and the body ground

Water temperature Resistance

60C (140F) Approx. 70 - 90 ohms
100C (212F) Approx. 21 - 24 ohms





now, where exactly is the thermal transmitter? I think i am looking at the right thing, is it sticking straight up next to the outlet pipe and the thermostat? Anybody able to post pics cauz the nissan manual isn't helping me......

[bagsy]

yeah , mines doing the same thing.It doesnt go over 1/5 aswell. Ive changed my thermostat and also pluged in a mates vdo electric temp gauge and it was reading 75 degrees celcius. Think I ll just get a vdo gauge , but if you find out any more info I d be interested too. Thanks and sorry about the hijack , but same problem..... shane.

[marin]

how does an aftermarket gauge work, does it plug into the original temp sender? and what are they worth?

[mkpatrol]

Forget the gauge, replace the thermostat (basics first). You will have have more problems with the thermostat then you do with the gauges. If the standard thermo doesn't work get one that opens at a higher temp. What teperature is at the radiator when it is at operating temperature?

[marin]

dont know what the temp is at radiator, but i think that may be the way to go, replacing the thermostat first

[GQAndrew]

Thermal Transmitter Check
Check the resistance between the terminals of the thermal transmitter and the body ground
Water temperature Resistance

60C (140F) Approx. 70 - 90 ohms
100C (212F) Approx. 21 - 24 ohms


now, where exactly is the thermal transmitter? I think i am looking at the right thing, is it sticking straight up next to the outlet pipe and the thermostat? Anybody able to post pics cauz the nissan manual isn't helping me......

On the diesel there are 2 coming out of the thermostat housing. If you are looking from the front of the car, they come out the right hand side of the housing, on the horizontal. The closest one is the Temp Gauge Sender, the other is the one that goes to the Glow Plug Controller (I believe?) Are the instructions you have definately for the gauge sender, or are they for the other one?

You Petrol or Diesel?

[mkpatrol]

dont know what the temp is at radiator, but i think that may be the way to go, replacing the thermostat first

Cheaper

[marin]

ive got a petrol that is on gas. I'm changing the thermostat at the moment, waiting for it to cool down so i can get it out, it is still the original nissan 1, also changed the fan clutch just b4, now the fan spins properly (i can't stop it with my hand like b4), and apart from that, just rang nissan about the temp sender unit, they quoted me $52 for it, so i think i'll hold off on that for now. guy at nissan suggested to me to check my wiring that nothing is pinched or nicked, will do that, might also pull temp sender out and just have a look, see if its something obviously wrong with it.

[mkpatrol]

Thats the go. Temp senders don't fail all that often but thermostats do. Temp senders usually fail after they have been cooked or are made cheaply (like in old aussie cars). Let me know how it goes. The cooling system is happiest at around 90 degrees but wont boil until over a hundred once it is pressurised.

[marin]

when i opened the thermostat cover, the thermostat was wide open, as the engine was still reasonably warm (read VERY warm, stupid me, that was dangerous to take that off, but anyway) and when i left it to cool, it closed itself up again, so i dont think that was the problem, but i changed it anyway, no change to the temp gauge. Tried to take the temp sender out, but as it was warm and seems to be made of brass, i slightly rounded 1 set of corners on it, but gave up b4 stuffing it totally (damn shifters!) Soooooooooooooo change the temp sender? about $50 from nissan, seems a bit steep,where else could i try to get 1 new?? Or i guess it could be my actual needle/gauge sticking......

[mkpatrol]

I really need to know what temp it is running at the radiatior. Do you have a thermostat for checking meat. plonk it in the rad & measure the temp. If it is between 90-100 degrees it is ok & maybe the gauge has gone out of range slightly.

[marin]

might be time for a trip to the supermarket to get 1... will post back here when done

[bagsy]

Hey marin, I got mine fixed tonite, the same problem....
My gauge was only rising about 1/5 and mines petrol gas also.

Test if the gauge is ok .Take the wire off the temp sender and earth it out. I just used another piece of wire and extended it to touch the negative battery terminal. Then check the gauge on your dash , if it goes straight up to hot, then the gauge is good....

And ive already changed my thermostat so it could only be the sender.

Trip to dandenong and 53 bucks and its all sorted.

Hope this helps, shane........

[marin]

awesome, an easy test for the gauge, thanks for that, will give it a go 2moz, the test in the nissan manual for the gauge involved pulling the dash out i think, thats y i didn't do it.

Did you have any trouble getting the sender out? cauz when mine was warm and i tried to get it out, i stripped 1 edge of the hex on the sender.... might do to pull it out when engine is cold...

[MKPatrolGuy]

awesome, an easy test for the gauge, thanks for that, will give it a go 2moz, the test in the nissan manual for the gauge involved pulling the dash out i think, thats y i didn't do it.

Did you have any trouble getting the sender out? cauz when mine was warm and i tried to get it out, i stripped 1 edge of the hex on the sender.... might do to pull it out when engine is cold...

Will come out much easier if you use a ring spanner instead of a shifter

[bagsy]

nope the sender came out pretty easy, mine was warm aswell. I was able to get a ring spanner on it though, 13 or 14 i believe.

Good luck.....

[mkpatrol]

Marin, the test Bagsy has described to toy only checks if the the gauge works, not if it is accurate. Most auto electritians have a resistance tester whech tests what the gauge reads at differens ohm readings set by the manufacturer. With this too he can check if it is accurate at any point on the gauge.
I had this check done on my MK & found that the gauge was faulty. Just trying to give you all the possibilities.

[marin]

well, changed temp sender 2night, $52 later and i think it is all good again, temp gauge goes higher than it did b4, to what i expected to be normal, i did that test earthing out the wire to the sender, gauge went above high till it couldn't go further, so at least it is working, (dont know about calibration), will have to wait for some warmer days, then will see if it goes up higher as the engine gets warmer, but i am confident that it will

Looking at the old 1, i noticed the plastic around the top of it was cracked and brittle looking, so it must be buggered from heat...... hope the engine hasn't been overheated b4!

[bagsy]

good work.....

[marin]

oh yeah, i used the proper tool to take the old 1 out this time, used a socket, no problems like last time, says something for my lazyness

[BLACKRAT88]

Hey guys i have a 4.2 dual fuel shorty and was wondering where the water temp sender is actually located?!?

[Clanky]

You guys should sell your dodgey low reading gauges to the other guys on another thread who have overheating problems.