Problem diagnosis required - punto running too cold

[Wing Commander]

I am in the process of prepping a mk1 punto for sale.

One annoying thing that has been common on this car for the last two years is that it runs under the normal operating temperature, according to the dash.

Thing is, I have flushed the entire coolant system more times than I care to remember, and bled it properly after. I have recently replaced the radiator and the thermostat, along with the temp sender plug (which feeds the dash) and the instrument cluster.


All of this, and it still runs just under a quarter. The thermostat opens as it should, letting hot water circulate once it starts warming up. Just leaving the car on the drive running pushed it just above a quarter when the fan kicked in and brought it back down to just under.




The new temp sender is clean and has a good water supply to it (water flowed out when I changed it).

I'm at a loss as to what it could be. The car runs fine, no problems, but I would like to sort it before I sold it.

Thanks

[kambites]

If the fan is kicking in when the temperature gauge is reading that low, then either the sensor that triggers the fan is broken, or the gauge is.

If the thermostat is opening (which I'm pretty sure it shouldn't at that temperature) then I'd say it's the gauge.

Edited by kambites on Wednesday 4th August 11:37

[Mr Gear]

I certainly wouldn't worry about that. That gauge won't be reading 0degs-100degs... it will start somewhere around 60 degs C, so the needle is reading about 80 degs C... perfect temp.

Does the needle take some minutes before it even moves off the bottom of the gauge? If so, I am correct and it's nothing to worry about.

EDIT: You could check the temperature by taking an infra-red reading off the radiator. This should be between 80 and 100 degs C. http://www.google.co.uk/products?q=infrared+thermo...

Edited by Mr Gear on Wednesday 4th August 11:40

[JC2012]

It could be the actual guage itself that is faulty?

It sounds as though you have replaced all the common bits you would expect to be at fault. Are you sure theres no other electrical connectors that measure the temperature that are possible paired or linked in anyway?

[JC2012]

http://www.fiatforum.com/punto/125524-temperature-...

Could be a dodgy earth or even the chances of a you buying a NEW faulty Thermostat might be worth trying another one.

[kambites]

Can you get it up to temperature and then stick an actual thermometer into the coolant to see what temperature it's really running at?

[Mr Gear]

kambites said:

Can you get it up to temperature and then stick an actual thermometer into the coolant to see what temperature it's really running at?

I'd use a non-contact thermometer to do the same job... radiator would be under pressure, so you can't just go dipping a thermometer in.

[kambites]

Mr Gear said:

kambites said:

Can you get it up to temperature and then stick an actual thermometer into the coolant to see what temperature it's really running at?

I'd use a non-contact thermometer to do the same job... radiator would be under pressure, so you can't just go dipping a thermometer in.

True.

[RobCrezz]

You sure that it isn't the right temp? 1/4 way is normal on my civic.

[Wing Commander]

I'm in no doubt the engine is performing as it should, as it goes through all the correct stages ie start up, idle for a few mins, start to see the needle go up,goes up a bit more, now start to feel heat in rad hoses, heats up some more and the fan will eventually come on.

I have replaced the temp sender and the dash cluster so thought they would both be ok. The cluster was second hand though, so can't be sure. Earth sounds like a possibility but not sure where it is. Will have a hunt later but you guys have put my mind at rest anyway so might not bother just yet!

[WOO5IE]

Water temperature senders and guages are not very high tech and in fact very basic technology and notoriously inaccurate. The main issue is what is normal and is there any variance to the 'Normal' reading.

Its sounds Ok and I would leave well alone.

[varsas]

Sounds OK to me however were this a classic car and it were reading low (and I'm not sure it is in this case, although I wouldn't expect the fan to cut in with the gauge reading 1/4) I'd be suspecting the voltage regulator. Dials/gauges need a constant 12v to work correctly, a battery/alternator won't supply that so you have a regulator which smooths the input down to 12v. I expect modern cars have something similar somewhere, maybe the voltage regulator on the back of the alternator?

The test would be the fuel gauge, does that also read low?

[Stoatman]

My civic was running too cold and it turned out that that themostat was stuck open so always cooling the block. Changed it, now its spot on and never wavers.

[Bollah]

[quote]along with the temp sender plug (which feeds the dash)
[/quote]

Are you sure it was that plug? I know some Fiat's (tipo's and coupe's) have 2 sensors, 1 for the ECU and 1 for the dashboard. Could it be possible you replaced the ECU one instead? (This is where you tell me it's a carb model )

[Wing Commander]

Fuel injection and yes, pretty sure it was the right plug!

TBH, just going to leave it well alone! Runs fine, fuel consumption fine, fuel gauge is fine.

Thanks everyone!