[crazy4saabs]

The heater in my 99 convert seems bewitched now that cooler weather has settled in. The heater works sporadically, seems like whenever it wants to (instead of when I need it to). The fan is working and blowing plenty of cold air in all settings. It is a manual heating and air conditioning system vs. climate control. Recently, I replaced the heater hoses when one of them sprung a leak. I replaced the thermostat about six months ago. I don't know if related or not, but I have noticed that it seems to take the car a very long time to reach operating temperature based on the dash guage. Even when the needle gets to the 8 o'clock position, still no heat in the car. Any help would be greatly appreciated.

 

[pokeyjoe]

You may have a bad thermostat. I've bought two thermostats that were garbage right out of the box (one for a Volvo and one for a Saab). The thermostat is easy enough to get to - pull it out and test it in a pan of boiling water. In your case, I'd make sure that its closing completely when it cools off.

 

[Pontius DIO]

An easy way to tell if the thermostat is opening is let the car warm up to normal temp. Put your hand on the upper radiator hose. It should be hot with the coolant circulating through it. To compare if it's hot enough, the lower hose will be really hot. Once the thermostat opens, it should be as hot as the lower hose. It's possible that your heater core is clogged. The rows can get mineral build-up over time just like a radiator can.

The way to tell if the heater core is clogged, is after the car is fully warmed up, grab the hoses going to the heater core. One hose goes in, one comes out. They both should be warm. If only one hose is mildly warm and the other is cooler, suspect a clogged heater core.

Double-check that you actually have enough coolant in the car. You mentioned replacing the thermostat before, did you put a racing thermostat in? They won't allow the coolant to get as hot.