Temperature gauge reading low?

Hi all,

I've been thinking about changing the thermostat due to the temp' gauge sitting right at the bottom of the scale recently. When I first got the car, the gauge always sat at around the lower bit of the Normal section but recently, it's been sat on the black block before the Normal range.

The reason I'm questioning if the thermostat actually needs changing it is because the fuel economy has remained constant at around the 37+mpg mark. I'd expect a stuck open thermostat to drastically reduce the economy.

I noticed today that with the ignition off, the gauge sits well down below the range of the gauge which got me wondering if it's the gauge which is showing low due to the low starting point. If at rest, the gauge sat at the start of the range, then running, it'd show pretty much bang on the middle of the Normal...

Anyway, I'm starting to talk drivel now so could someone tell me if this is normal for a temp gauge at rest or whether it's sort of slipping down? It's an early analogue dash by the way.

I think when its turned off the gage is inactive so is at its default position?

The thermostat allows the coolant to flow when it reaches the right temperature, so is not directly linked to the gauge.
The gauge should read whatever temp the coolant is.

Do you have any over heating issues? Does the radiator get hot all over?

If you don't have any over heating issues and the radiator gets hot all over, I would be more inclined to start by looking at the temperature sender.

Below the coil pack, you'll find the temp sender for the ECU (has a two pin plug on it) and I think (but not 100%) the sender for the gauge is below that.

Lecky off



But as your fuel is showing then I guess you have lecky on and mine then goes up to this, car is cold at the mo so this is where it starts then goes up to half way when warmed up, with no air locks in system



hope this helps

topmansparkie said:

The thermostat allows the coolant to flow when it reaches the right temperature, so is not directly linked to the gauge.

Click to expand...

if the stat is faulty and stuck open, then it will allow coolant to constantly flow around the rad which would cause the temp gauge to read cold like that

Wot Steve said.

But if stationary for any length of time on a hot day (No idea where you'd find one of them) it should start to climb as no air is now flowing through the rad and the fan shouldn't be running.

Thanks for all the replies! I don't get any overheating, the heating still works fine after a few mins running and sitting in traffic doesn't budge it. I'll have a feel of the top and bottom hoses to see if they're getting uniformally hot. I'd tend to agree with Steve as well, but it's not showing any signs of a stuck 'stat... The running reading has just got lower over the last 12 months but it never read anywhere near the middle.

Sorry to revive this old thread, but did you manage to fix this?

I have the analog dash and I'm having this same issue: The temp gauge always reads low, but it's working, as if you just let the car warm up for a few minutes, you see it moving up to the first black square and shortly after the fan will start and it will go down again.

The temp sender unit has just been changed and it didn't resolve the issue.

As far as I know, the analogue dash models have a separate temperature sender for the gauge and the other one is for the ECU. Re read all the posts, as the 2 sender's/temp sensor are described. Mine has a digital dash so only has the one sensor.

@danihxh i joined this thread as you had posted just over a year ago and perhaps you are still experiencing the problem.
I have a 2001 Ford fiesta however it shares the exact same gauge cluster as the puma and has the same problem as the second image in @lrrhood’s post. It has nothing to do with coolant temperature sensor as I started there before doing any sort of diagnostics and found that the temperature of coolant is being read by the ECU/PCM.
Only just found this out after several months of pondering what it could be, if you put your key into the ignition, hold down the trip reset button and turn the key to position 2 without turning the engine on, the word test should be displayed where your mileage count usually is. When the word ‘test’ appears, let go of the button and then press it again and it will take you into a sub-menu that will allow you to scroll through (by pressing the trip reset repeatedly) where you can perform a gauge cluster test and it will also at one point give you a live coolant temperature read out. When I performed the gauge test on my car, all the other gauges swept over as far as they can go but the temp gauge only reached just past half way which makes me unsure whether the needle needs resetting to it’s true zero or if it is an electrical fault.
When I scanned my car for fault codes, a P0115 fault code came up which is ‘ECT (engine coolant temperature) circuit fault’. This code did not illuminate the check engine light but was a stored fault code.
If I come to a conclusion with the problem I will post it for anyone else having the same issues.

I had P0115 on my Red Puma, replaced the coolant temperature sensor last week and the fault code has gone. The car was built in 08/99 and doesn't have an EML, Forscan found the error code as well as P1000, which I've ignored.

Good grief! I never knew you could do the trip switch thing!