Where on earth is my outside temp sensor wire?

[VectraGoVroom]

So my car has never had that outside temp sensor while I've owned it. I've got the sensor now, but I can't seem to find the wire. Could someone help me out and describe the connector, where it comes from and where it may be tucked away? I've discovered one two-pin plug hidden under the center grille, could that be it? I'd rather not plug the sensor in and risk frying it or something else if it ends up being the wrong plug.

[Lowrider Dave]

The sensor 'plugs into' the front bumper on the passenger side near the front. The wiring will be in that area if you have it - the plug will be blue, thus:



(TonyO's photo)

[Robsey]

You may not have the wire from the engine bay bulkhead to the front bumper.

There will be a connector on the euro-mainland driver's side of the bulkhead.

It will have two wires in it.
One wire is blue.
One is blue with a white stripe.

You need to extend these two wires to the front bumper.

If it helps, the temperature sensor and plug is the same for all Vectra-A, Vectra-B, Astra, Corsa and Omega.
So plenty of potential donor vehicles in the salvage yard or on ebay.

[VectraGoVroom]

Thanks, both of you.
Robsey - That connector is the wide one with a bunch of unused terminals, correct? I was wondering what that was for. I assume both are the standard Bosch connectors, like this.


It might be easier and cheaper to pick up some connectors and wire, and put together that loom myself. Am I seeing Dave's picture correctly, that's the striped wire on the right side of the sensor? Or does polarity even matter in this case?

[Robsey]

It should not matter which way the sensor is wired.

The sensor is simply a resistor who's value changes with temperature.

And in Daves image, the near wire is blue, and the far wire is the blue with white stripe.

[VectraGoVroom]

Hey, I found the wire! It was tucked away next to the radiator, with an old busted sensor still on it. The reading didn't seem that accurate, but maybe the sensor just hadn't cooled down from room temperature yet. Now I need to find a route to get the wire to that bumper, any help?

[Robsey]

It sounds like the bumper has been pulled off, and the sensor has been ripped out of it's socket.

From memory -

The routing of the wire should be from the bulk head.
Around the outside of the suspension turret towards the front of the car.

Along the inner wing.
Through a hole behind the headlamp assembly and down towards the ground.

Between arch liner and the bumper.

Then clip into the bottom lip of the bumper, with the centre probe pointing down.

There is a hole in the lip about 15mm diameter. The sensor has three barbs or tangs that clip through this hole.

[VectraGoVroom]

The bumper absolutely has been taken off, the car was a write-off from a big front end crash, and my brother bought her and fixed her up and gave her to me for my eighteenth birthday! That sounds like good advice, I'll need to go under the hood again tomorrow. The sensor says it's +10C while it's actually -5, I need to get it out of the engine bay and onto the bumper. Who knows, maybe the connections actually are corroded and I'll need to make up a new loom.

[Robsey]

Maybe your brother thought that the sensor should be located near to the radiator.
It is in a lower member in front of the radiator but behind the grille on most other Vauxhalls including Astra F & G, Vectra B & C, Corsa A to C.

But the Cavalier (Vectra-A) is different, and it is in the bottom lip of the front bumper on the left side.

Being different is what makes the Cavalier special - ha ha.

So you simply need to feed the wire back out from near to the radiator, back towards the bulk head. I cannot see it reaching all the way around the inner wing, and to the front of the car near to the radiator, so it is probably mis-routed.

If it is reading warm, is that because it is near the radiator?

Normally these things fail in two ways.
Open circuit - so you either get -40 degrees Celsius or F on the display.
or
The sensor is going odd and starts reading warmer than it should.
I have fond memories of my sensors telling me that it is +43 degrees Celsius.
Not likely in the UK... and I have never taken the car to any African or Middle-Eastern states. - ha ha

These sensors are very cheap (well they are in the UK), and will fit from many other Vauxhall / Opel models.
If it isn't localised radiator heat making the error, then I would indeed suspect your sensor is going faulty.

[VectraGoVroom]

Got it. The sensor's on the bumper now, still shows about four degrees too warm. The sensor's brand new, but it's a generic one from China. Could it just be an inaccurate sensor, or could the wires or connectors be faulty?

[James McGrath]

Not sure if it's the design of the sensor itself or the chip which calculates the temperature based on the sensor's readings but I've always found the reading to be a bit vague.
I also think they are a bit slow to react to a change in temperature.

My CD manual which has a genuine sensor is currently reading 8.5 C and the V6 with a non genuine sensor is reading 9.5 C.
The current outside temperature is 7 C

So 4 degrees isn't that far off. I would say you've got it wired up correctly.

[Robsey]

Hmm - a whole 4 degrees. Yikes.

Mine always seems "about right", but it only really matters for judging ground frost temperatures.

Below -3 and you can tell it is flippin' freezin'

Above 20 degrees and the windows need opening. (Unless you have an air con equiped car). The give away is perspiraion on your forehead.

What more do you need to know... ha ha.

[VectraGoVroom]

-3 is "flippin' freezing"? Greetings from Finland: Weeeeeak.

The temperatures I'm most worried about are the ones hovering around zero. A little sunshine turns snow to slush, some night frost turns slush to ice, some rain lubricates things nicely and the roads become a damn skating rink. We just got first snow last night, luckily I've got some brand new winter rubber. I should do an update on the car's thread again, I've been busy with her...

[Robsey]

Ah yes - Finland... what a great place and lovely people.
Land of the mid-night sun in summer.
Had lovely times in Rovaniemi.
Only about -17 and -7 the two times I stayed.
Managed to dress in normal UK clothing.
In fact it was so warm on our second trip we had to keep the window open all night.

The winds are flaming harsh off that wide river though.

I agree with what you say... and I stand corrected.
It will indeed be what the temperatures either side of zero that matter to you.

[cavalier1990]

Thought mine was gubbed as well so I bought a Siemens one off of that famous auction site, cost a tenner, not sure it's settled in and reading correct temp now but about to go find out by referring to airport temp and what car is reading! All i know is it is coolldd tonight!

Pity we couldn't calibrate the damn thing isn't it Robsey sure there must be a way.

Update: mine is reading -5.5oC and it is about 2-3oC in town so a bit of a difference, although I am a bit out in the sticks away from warmer town area, still a good bit out I would think though.

[Robsey]

Hmm - possibly a resister shunt to allow a %age correction.


There is also a speed sensor wire on the temperature displays. It is supposed to be to allow correction in relation to the speed of air rushing past the sensor tip.
The wind chill factor.

[cavalier1990]

Hmm - possibly a resister shunt to allow a %age correction.


There is also a speed sensor wire on the temperature displays. It is supposed to be to allow correction in relation to the speed of air rushing past the sensor tip.
The wind chill factor.

Interesting factoid that!

[VectraGoVroom]

Hmm - possibly a resister shunt to allow a %age correction.

I was thinking about that! Maybe I could just splice in a potentiometer on the display end of things, then measure its resistance at the correct setting and replace it with an actual resistor if I wanted to get fancy... Off to the bay of E.

[Robsey]

I wonder whether this would be accurate on the whole temperature range, or in only a small narrow band of temperatures where you would need to set it for best accuracey where you actually rely on it the most.

With regard to actual temperature...
I live 165 yards up a hill, and it is always between 0.5 and 1 degree colder up here than down at the bottom of the hill where it is more sheltered.