I have a 1991 GMC sle sierra truck and my heater only blows when my truck warms up and sometimes that's a long time. Do I need another heater core?
That's how they are. All my tbi trucks only blow heat when they get to operating temp. But it only takes a couple miles for it to get there for me. If it's taking much longer then maybe your thermostat is hung open alittle
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