Randomness of the temperature gauge.

[Tdafforn]

Over the summer I fitted a digital temp gauge alongside the original smiths gauge. Just drove to Brighton from the Midlands via the M25 on the hottest day of the year. Glad I had the digital gauge. The Smith one is way over sensitive. It didn't actually get into the red but it did get close. But the digital gauge showed the temp, at its highest was 95oC and only momentarily. I could also see the thermostat cutting in and out at 88oC on the digital gauge which matches the thermostat setting.
just shows you a hot stag is sometimes only hot because of the gauge.
tim

[Wheelz]

My temp gauge over-reads very slightly but is not very sensitive, it hardly moves. In contrast the digital gauge responds to the slightest change. On this very hot Wednesday, initially after it had warmed up it then steadied at about 82C, but after a fast run, then when stopped in traffic it crept up to about 90C and stayed there. Not bad for a 50 year old considering they were known for overheating. I do have a fan cowl which really helps though.

[Rubce]

Which digital gauge did you fit Tim?

Regards

Bruce

[RobinLegin]

Beginning to suspect my temperature gauge. This was the reading on our way down to Switzerland on the A6 towards Beaune. It was 33C outside and certainly hot under foot. I reduced speed to 60 mph to avoid the needle going into the red. Yet the thermostat is one that opens at 72/74 C. IMG_6381.jpg

[Tdafforn]

This one.

[trunt]

I believe that all of the temperature senders available nowadays tend to overread, mine certainly did.. they seem to have lumped many part numbers (which may be slightly different) under one part. I have an ewp and it’s running at 90C, the controller is good at keeping it bang on.. I just added a resistor to the sensor line to bring the needle down to mid point, it still reacts, I see the thermostat opening and it will still indicate a little lower when I am running at 85 degrees as I do in the winter.

LD parts sells a sender that claims to read lower than the commonly available ones.

[Wheelz]

I believe that all of the temperature senders available nowadays tend to overread, mine certainly did.. they seem to have lumped many part numbers (which may be slightly different) under one part. I have an ewp and it’s running at 90C, the controller is good at keeping it bang on.. I just added a resistor to the sensor line to bring the needle down to mid point, it still reacts, I see the thermostat opening and it will still indicate a little lower when I am running at 85 degrees as I do in the winter.

LD parts sells a sender that claims to read lower than the commonly available ones.

Adding a resistor can only make it accurate at one point, and even worse it can mask an overheat

[KOY 23]

Beginning to suspect my temperature gauge. This was the reading on our way down to Switzerland on the A6 towards Beaune. It was 33C outside and certainly hot under foot. I reduced speed to 60 mph to avoid the needle going into the red. Yet the thermostat is one that opens at 72/74 C. IMG_6381.jpg

Operating temperature =heat put into cooling system by engine - heat removed by cooling system by radiator etc. Normally it’s around 90deg C. Fitting a low temperature thermostat will not change the operating temperature, only the temperature that the thermostat opens.

[jbuckl]

All the items are referred to as instruments.
That may seem to imply a level of accuracy (unknown)
Imho they are or should be regarded as guides or for indication only.

Unless you calibrate them… they remain just guides.

[DJT]

LD parts sells a sender that claims to read lower than the commonly available ones.

I have had two senders from LD. With the first the needle only reached vertical on a really hot day, the 2nd reads as per the photo in post 4. 88 degree stat.

[Tdafforn]

I think the real issue is the accuracy of guages. Whether it is the guage or the sender. The one I have(which uses a sender fron LD) reads too high and is way too sensitive. When it read 135oc it was actually 90oc. Reading 90 oc was more like 75oc ... true a resistor won't sort this sort of scaling. I'm going to by a new smiths guage and sender and see how that works.
tim

[trunt]

The gauge can be calibrated, may be worth trying before buying a new one.

[Tdafforn]

What i found very interesting is that the digital temp probe showed that when we were in slow moving traffic on the m25 the water temp would repeatedly rise to about 90 and then drop really quickly to 85... I can only think it was the thermostat as the fan was on the whole time.
the speed of the fluctuation was rather faster than the normal temp gauge would be able to pick up
tim

[KOY 23]

What i found very interesting is that the digital temp probe showed that when we were in slow moving traffic on the m25 the water temp would repeatedly rise to about 90 and then drop really quickly to 85... I can only think it was the thermostat as the fan was on the whole time.
the speed of the fluctuation was rather faster than the normal temp gauge would be able to pick up
tim

Sounds like the thermostat is doing its job. Gauges are damped to hide variations that do not matter and worry drivers, exactly what a digital doesn’t, a waste of money and time IMHO. Modern cars are programmed to indicate a temperature that keeps the driver happy. Once warmed up mine sits at 90, weather idling on hot and cold days and being driven hard, of course the actual temperature changes, which is normal, but does it matter, of course not. It’s the trend of the reading that matters.

[Dorian]

Where did you put the sensor for the digital thermostat Tim? I'm not suggesting that would account for your large differential readings but small changes in position can make surprising differences.
The digital should be more reactive but all have either preset or settable filters.
I have one controlling the fans and for this the sensor is at the bottom side of the radiator near the hose.The return temperature rarely exceeds 67c even with a 100mm thick intercooler covering most of the radiator!