1992 Deville No Heat

Hello, Just wanted some opinions on my heat problem. So far I have flushed the heatercore both ways(reattached hoses properly), flushed coolant system, changed thermostat(in its right direction), refilled radiator and reservoir to proper level. I have functioning brake release, and dont hear a vacuum leak. I had heat last winter. I guess it is the heatercore, but both hoses seem hot(the bottom one seems hotter). There is also no leak from the heatercore, and only one code E91. Thanks guys.

E91 is a PRNDL switch problem, probably not related to your heat problem. Sounds like you may have a problem with the temperature door or the controls for it.

sorry I left out that I have the dash apart, and see the door move when I change the heat settings.

was the heatercore