No heat

Good morning.

It sounds like your heater core is partially clogged with debris. I would have it flushed out to get rid of the debris. At idle there is not enough circulation to get the heat to work.

Roy

HVAC is not my specialty, but I would think you are probably low on coolant. With the engine off and cold, check the coolant level. Refill it as necessary. Warm it up and see if it improves.

If it is low, that means that you have a leak somewhere. What you would do is borrow a cooling system pressure tester from AutoZone, Advance Auto, or O'reilly Auto Parts and hook it up to your radiator. Pump it to 15 lbs and go look for a leak. Here is a more in-depth description of what to do: https://www.2carpros.com/articles/radiator-pressure-test

Let us know what you find.

I had checked the coolant level prior to writing and the level was just short of full. I had the radiator flushed in the fall of 2017 just before winter so is the heater core being clogged still a possibility? Or should that have been flushed when I had the system flushed and new coolant put in? (Meaning should I go back to the dealer and complain that something was not done correctly)

I would still have the heater core flushed. Use a garden hose and air to blow out the debris.

Sometimes flushing the radiator frees up some gunk and it just goes and collects in some other spot with fine passages (like the heater core). What you can do is have a mechanic flush the core, or you can open the hood, find the two hoses right next to each other going into the firewall (the wall between the engine and dashboard), disconnect those hoses at their other ends, and hook the aforementioned garden hose up. Turn that hose on with low pressure and then gradually build it up. If a clog is your problem, it will take a few minutes of running at near full pressure before it is cleaned. Then turn the water off and put it back together. Presto! Doing it yourself just saved you $50.00 over taking to the dealer and it only took fifteen minutes. If you need more specific information, check out this general guide on heater core replacement or do a YouTube search. Here is a YouTube video that I found with a quick search: https://www.2carpros.com/articles/replace-heater-core

Good luck and let us know.