We need to first see how hot your truck is actually getting. What does the gauge say? It should run about 210 degrees. If it is, feel of both hoses going into the heater core, through the firewall. Is one hot and the other cool? Or cooler? If so, the water may not be circulating through the core. Keep in mind that if the water is circulating, and the blower is on, blowing air through the core, the water temperature on the outlet side of the heater core will be slightly cooler. If the water is not circulating through it, one will be considerably cooler. If this is the case, I only recommend replacing it. If it appears to be circulating, I would start checking the operation of the blend door in the evaporator case. If it is mostly closed off to the core, little or no air will pass through the heater core, thus no hot air will reach your cold face or feet try that. If the truck is, in fact, not reaching 210 degrees, replace the thermostat.
Also, it could be a blend door actuator acting up.
Please run some tests and get back to us so we can keep helping you.
Monday, September 14th, 2020 AT 11:03 AM