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2002 GMC Sonoma won't heat up past 150 degrees

I had a radiator split last summer. changed it out and now it won’t heat up past 150 degrees. i cleaned heater coil, changed 3 thermostats. 2 radiators and heat temp console. plus temp sensor.

Thermostat installed backwards, maybe? Air bubble that just can’t get out?

How are you measuring the 150 degrees? With the car’s gauge or sender? Or something else? I wouldn’t believe the car’s gauge or sender unless I’ve verified it with another method.