Water Temperature Sensor Fuse

[MrAl]

Hello there,

[1998 v70 non turbo]

Been a while since i posted here got into a lot of other stuff recently.
I've had a problem with my sensor for the water temperature but i hear there is a fuse somewhere and was advised to check that first. The problem is, everywhere i looked seems to have no information about where this fuse is.

Could it be inline, or perhaps shared with another device in the car?
Anyone know where i can find this fuse?

Thanks in advance.

It's so amazing that there are hundreds of articles and posts on the sensor itself, but none on the fuse or at least none that i could find and i searched for quite a while and i dont give up too easy

Thanks a lot.

[scot850]

I have never heard of a fuse for the temp sensor. Well not one specific to the sensor. Do you mean a relay? There is a fan relay that gets its signal from the ECT. It is mounted on the inside of the slam panel above the radiator. If this is bad or had bad connections it would cause the fan not to run or possibly not at the correct speed.

I think you would already know how the ECT can go bad on these cars (especially if aftermarket part is used). The connector at the back of the steering pump and the wires are a known issue as well. Checking for clean contacts and wires there is very important.

Lastly, a sticking thermostat could also cause variable readings.

Neil.

[abscate]

A sensor like that will use a regulated power supply from the ECU and a return line showing the voltage drop as the coolant temperature changes. The power supply from the ECU will be current clamped so it doesn’t need a fuse for protection.

The typical resistance of the ECT is1000 ohms , so a 12V source would mean atypical current of only 0.010 amps, or 10 milliamperes.

[MrAl]

I have never heard of a fuse for the temp sensor. Well not one specific to the sensor. Do you mean a relay? There is a fan relay that gets its signal from the ECT. It is mounted on the inside of the slam panel above the radiator. If this is bad or had bad connections it would cause the fan not to run or possibly not at the correct speed.

I think you would already know how the ECT can go bad on these cars (especially if aftermarket part is used). The connector at the back of the steering pump and the wires are a known issue as well. Checking for clean contacts and wires there is very important.

Lastly, a sticking thermostat could also cause variable readings.

Neil.

Thanks for the info i didnt know about the thermostate too. Have to check that also.

[MrAl]

A sensor like that will use a regulated power supply from the ECU and a return line showing the voltage drop as the coolant temperature changes. The power supply from the ECU will be current clamped so it doesn’t need a fuse for protection.

The typical resistance of the ECT is1000 ohms , so a 12V source would mean atypical current of only 0.010 amps, or 10 milliamperes.

Hello again,

Oh ok, thanks for the info.
Been having some problem with this for a while now. Turn the car engine off, radiator cooling fan keeps running, runs the battery down. How stupid is that. I guess it is time to fix it. The battery was getting older now anyway but i found out something important i will mention here for now...

The jump starters now come in two flavors: Lead acid (old style) and Lithium ion or similar (new style).
Well i picked up a Lithium based unit a while back and the day befpre yesterday i had to jump start the car. The weather was not too cold, somewhat mild. The car turned over about 5 times but would not start beacuse when it sits for a week it has to turn over more times before it will start. Unfortunately, the Lithium based units use Litium ion or polymer batteres, and though this is a better technology than lead acid in general, there has to be enough cells in parallel to deliver sustained high current or else the cells will overheat and even catch fire (see videos online). So when they design them they have to include a time out function because if you use too few battery cells you have to force a shorter run time, which means the car only gets a jump for about 5 seconds. So if the car does not start in about 5 seconds it times out and you get no more power so you have to get out of the car, unplug the connector from the unit, then plug it back in and connect the jumpers to the battery again. Then you can get back in the car and try again. Well, i did that 3 times and found that the car engine really needs a longer boost time than that so i gave up after the three tries. Lucky a neighbor was outside at the time and we used his 100 amp plug in jumper booster to start the car. It's a really good charger/booster so after a minute or two it started right up.
Next day however (yesterday) it was down again, and it was nice and warm out about 70 degrees F. It turned over about 4 times without a jump but that wasnt enough because the battery was low and so it turned over too slow.
I almost gave up, but then decided to try the little Li-ion based jumper unit again. This time it started the car but it only took about 4 engine turns to get it to start and it was very warm out.

So in conclusion i cant recommend these new types of portable jump starters unless your car can start within maybe 5 seconds. That means a really bad battery wont cut it and a slightly harder to start engine will never start. In that case i would stick to the Lead acid based jump starters. They are more expensive and much heavier, but that is the only way.
That's of course if you dont have access to a regular 120vac outlet where you can charger the battery for a while with a decent plug in charger before you start the car. I cant do that really because i have to run an extension cord across the driveway and in winter it gets a little more risky with the wet snow or whatever, and of course if you are at the grocery store you dont hafve access to a 120vac outlet anyway.

Well thanks again for the information it will help me solve this.

[MrAl]

I get some good help here so maybe this will help someone one day.

When the coolent temperature sensor goes bad or just something like the connector is bad, the cooling fan runs even after the car engine is turned off. This drains the battery significantly as the motor in that fan draws a lot of current (the fuse is 60 amps).
The fan can run for up to 3 minutes so it readly kills the battery after a few times. I found out the hard way and had to purchase a new battery over 220 dollars (USD).
The fan still runs of course, but now after i shut the engine down i pull the fuse to the cooling fan. That stops the fan from running. I put it back in when i have to go somewhere and pull it out again once i get there.
I will be fixing this soon though as that's the best way to handle this, but if you cant fix it right away at least you can pull the fuse to prevent the battery from draining.

[scot850]

Some of these cars (may depend on region) do have a fan run on feature to cool the engine after running for a while. My turbo gets really hot under the hood on hot days so it can run on for a while but not continuously to run the battery flat.

As you say, a bad temp sensor or fan relay can cause this to run on.

Neil.

[MrAl]

Some of these cars (may depend on region) do have a fan run on feature to cool the engine after running for a while. My turbo gets really hot under the hood on hot days so it can run on for a while but not continuously to run the battery flat.

As you say, a bad temp sensor or fan relay can cause this to run on.

Neil.

Hi,

That's interesting, i had not thought about the relay i'll look into that also.

I thought it would be the sensor becuase it is kicking on the PO116 trouble code which points to the sensor. Not sure if it could be for the relay too, but i guess i'll find out soon. I was thinking even the connector to the sensor as others have suggested.

[abscate]

It’s always been a curiosity of mine thst if you unplug the MAF and run my ME7 cars, the radiator fan goes on amd does a several minute afterrun , independent of outside or engine temperature

It’s probably a default limp code in the software thst does this

[MrAl]

It’s always been a curiosity of mine thst if you unplug the MAF and run my ME7 cars, the radiator fan goes on amd does a several minute afterrun , independent of outside or engine temperature

It’s probably a default limp code in the software thst does this

I forgot what an MAF is, but the sensor and thermostat has been replaced now and the fan no loner runs after turnoff and the gas mixture is back on track, so i guess it will be ok now.

I have a feeling that sensor was "iffy" for a long time now it would run rough all of a sudden sometimes.