Temperature gauge and A/C stop working

Engine Cooling problem V8 Two Wheel Drive Automatic 49000 miles

Twice coolant temperature gauge has failed to register pass 100F. After approximately 10 minutes driving time, gauge warning light came on and AC quit working. Engine is not overheating. Dealer replaced thermostat after first occurrence. Problem came back few weeks later but self corrected - gauge started working, warning light went out and AC came back on. Gauge readings are erratic at times - between 165 and 210 ( 1/4 mark to 1/2 mark on scale ). Gauge never reads past 220. I have Chevrolet TrailBlazer LS 2008 ( American Version ) having 65000 miles

I am facing problem of dropping of temperature gauge while driving. It comes automatically down after some time during driving. One of the mechanic has replaced temperature sensor but problem still persists. Moreover, once temperature needle goes down to zero during driving, Air conditioning COOLING system also stops working during that period. Sometimes temperature needle works perfectly fine and sometimes drops automatically during driving. Once mechanic RESET from computer, it becomes ok but again same thing happens after few days. I am really so worried. Please help me to resolve this issue.

The dealer have change the coolant temperature sensor, water pump and also the dealer try to fix wires lose but it does not fix the problem. Could it be because of the battery?

Intermittent temp gauge and of course the AC stop by default when that happens. So, What's the big secret? This thread is listed under. This thread started 6 years ago and there is no answer to this VERY COMMON problem?

Not just here but threads all over the internet with no answer. You can leave off the list Temp sensor / Thermostat / Wiring. It's none of these. LoL!

Hal

Any ideas on problem?

My question is for Ken the Admin. How does the BCM affect the temp gauge? My '08 trailblazer just developed this problem. I cleared the code 128 and the gauge is working fine for now. I expect it to be intermittent.

Today my service engine soon light came on and my engine coolant temperature gauge dropped below normal range. Then it would start fluctuating back up to near normal than back down. Can you please help me? Thank you

Im just a shade tree mechanic my gut sais thermostat needs replacing but might as well change temp. Sensor also thermostat behind alternator comes as housing my check engine lite was engine not reaching proper temp when I turned on the heater it went to 210 and lite went off so im changing thermostat and antifreeze its usally a good idea to change about every 5 years my experiance.