page 75 is the first page of the troubleshooting section of the manual for that particular vortex meter.

Link

Dear,

I'm looking a remote reading temperature indicator to measure the temperature downstream a TCV in the cooling circuit diesel engine.
with the following specifications:
Thread: 1/2"
pipe sizing: 2"
measurement Range: 0-150ºC
Measuring product: cooling water of the diesel motor for fire water pumps
Capillary: Stainless steel with S/S protector
Capillary length: 10 meter

Your insights are highly important to me to determine the right model

Best Regards,

You may be dealing with a partially full pipe or air bubble. If that is the case, the indication will be erratic.

Just realized you last post is dealing with a temp. sensor. Temp readings don't cause flow meter fluctuations, in your case.

Vortex meter turndown is typically 10:1 of calibrated range. See page 3-20 of the link @danw2 posted : - there is a feature for low flow cutout. Check if your flow is below 10% of calibrated range.

From the beginning of installation if you don't have this problem, may be the flowmeter electronics would have got problem, better to replace it, otherwise if you have this problem from installation then better you contact the OEM person of that flowmeter and let him install it.