Temperature gauge problem 2009 Peugeot 207

[regsmyth]

Hi All,
Looking for some advice re the above. It's my daughters car, and she noticed that the temp gauge was not registering.
At some point she fiddled with the wires and noticed that the needle began to move.

I have had a look into it.
At first I noticed the connector onto the sensor was disintegrating, so assumed this was the problem.
I got a new coolant sensor and connector, and replaced both.
Went for a 5 mile drive and the needle didn't move.
Stopped to look at the manual, (engine running) and noticed that it was beginning to rise very slowly. After about 15 mins it was on 90.
As soon as I drove on, the gauge dropped back to zero.

The heater is working fine. I now suspect the thermostat, but I'm not sure if a failing thermostat would give the symptoms described.

Any help much appreciated,

Thanks.

 

[Old Salt]

To test the gauge touch the connector to earth (any metal part of the chassis) it should show full deflection towards hot if its working. Ignition on but engine doesn't have to be running.
To test the thermostat put it in a jug and add some boiling water and see if it opens, as the water cools it should close. Cheap enough to replace if needed, use a new gasket and make sure the surfaces are clean.

 

[carmanmemoranda]

Does the heater produce hot air or blows cold when driving at all ?

 

[regsmyth]

Thanks for the replies.
The heater does blow hot air, although I'm not sure it's as hot as it should be.
I think the symptoms I'm getting are indicating a "stuck open" thermostat.
So when driving, the radiator is keeping the water too cool to register on the gauge, but warm enough for the heater matrix. When I sit for a while with the engine running, it gradually begins to rise, as the radiator isn't doing any cooling. When I drive off, the radiator cools the water again, so the gauge begins to drop.
I'm going to get a new thermostat - it comes with the housing - £65 at ECP. Will let you know how it goes....

 

[norseman]

Sorry but this doesn't sound like a thermostat issue to me, more like electrical.
Some modern cars (BMW for example) have a electric heating device in the 'stat. housing that is controlled by the ECU .. something to do with economy/emissions?
Don't know if PSA group cars go in for this level of complication

nb. if you have an electric cooling fan is that being over-active?

 

[carmanmemoranda]

Sorry but this doesn't sound like a thermostat issue to me, more like electrical.
Some modern cars (BMW for example) have a electric heating device in the 'stat. housing that is controlled by the ECU .. something to do with economy/emissions?
Don't know if PSA group cars go in for this level of complication

nb. if you have an electric cooling fan is that being over-active?

I have to disagree with you, definitely sounds thermostat stuck open to me. But I will be interested in the outcome.

 

[norseman]

I have to disagree with you, definitely sounds thermostat stuck open to me. But I will be interested in the outcome.

Me too.
I hope I'm wrong as my suspicions may lead to greater expense for the OP. Hopefully the design of a 13 yo mainstream car is still fairly basic.

 

[Old Salt]

Always worth doing some basic testing first to try to identify the problem.

 

[Burnerman]

Always fit an O.E quality sensor......I can't remember the last dud thermostat that I had, but the symptoms do look that way.
John

 

[Mottie]

nb. if you have an electric cooling fan is that being over-active?

That wouldn’t make any difference if the thermostat was working properly. It’s the thermostat stuck open as the OP suspects.

 

[johnny2007]

When I sit for a while with the engine running, it gradually begins to rise, as the radiator isn't doing any cooling. When I drive off, the radiator cools the water again, so the gauge begins to drop.

Yes, you're correct.
Thermostat stuck open.
Being an older car I would get a good quality after market rather than give lots of money to the main dealer for the same part.

 

[carmanmemoranda]

Always worth doing some basic testing first to try to identify the problem.

not as easy as it sounds to test a thermostat now as it used to be. Very rarely are they actually just a thermostat now. mostly come in a housing, often physically unable to even see the stat now

 

[johnny2007]

not as easy as it sounds to test a thermostat now as it used to be. Very rarely are they actually just a thermostat now. mostly come in a housing, often physically unable to even see the stat now

That's where the internet becomes useful.

This for example

 

[carmanmemoranda]

That's my point. Changing it is as easy as testing it, or easier

 

[johnny2007]

Well, all symptoms point in one direction: thermostat stuck open.
I would just replace that for £50 rather than go to a main dealer and pay 5 or 6 times that for the same think, possibly done wrong.
Just have a look at all these cars with fsh from main dealer.
Most of them are missing half of the trim screws and undertray locking nuts.
Or, the undertray has never been removed because their idea of a full service is to suck some oil with a pump and refill.