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2008 Chevy Uplander Heater Problem in idle - DIY FIX
2008 Chevy Uplander with 57,000 miles. This winter, the HEATER began pumping out cold air when stopped at traffic lights or idling to warm it up in the driveway. Unless I had 1200 RPMs, I was not getting any heat.
After doing some on-line research, with the engine OFF, I added DEX-COOL 50/50 with water to the reserve tank. The level had been low by about 16 ounces. It made no noticeable difference at first. I decided the lines were probably clogged as well. I took the van for a spin with heater running at max heat, full fan speed and gunned the engine it a few times forcing it to downshift and rev to about 4000 RPMs. Parked it and noticed about a 5% improvement.
Two hours later, took it for another run, heater on, gunning it to 4K several times in 10 minutes. Parked it and let it run in idle. The air coming out was warm - not quite as hot when rolling but at least it wasn't blowing cold anymore.
Third run, repeated procedure and now all seems well. Air blowing from heater is nice and warm - even at low speeds or when idling.