Heater only works while moving

[PDXPeter]

When I stop at a light or something the heater will start to blow cold outside air. Within a couple seconds of driving it will blow warm air.

First thing I checked was the coolant and made sure it was bled fully. It is.

Ive read that there is a second thermostat that controls flow to the heater core. Where would that be? The temp gauge on my dash tends to hover around the first white tick mark tending to stay to the right of it while driving and to the left of it while idling.

[325e '87]

I don’t know the exact history on that second heater line thermostat but I believe it was a recall on the later year models designed to close the system if the coolant got too hot from an engine overheat, the idea being that if the heater core bursts it would burn the feet of the passenger.

If your car has one it is located under the intake mani at the heater core inlet. I deleted mine and I think most folks delete it. Realoem shows it pretty clearly.

I don’t know it its your problem but it is one of those things that can cause headaches.