My wife's got a 1999 SC2 with an automatic trans. I had to drive it the other day and I discovered that the heater barely works. The blower motor works fine, and I know that the coolant level is good. It doesn't overheat, but the temperature needle doesn't move past the 1/4 mark on the gauge, it's been that way since we bought it last winter. As far as I know, the heater worked then.

I don't think it's the heater core, as the windshield doesn't have a film of coolant on it, and the floor on the passenger side of the car is dry. It's not leaking coolant anywhere. Any ideas as to what it might be?

I'm going to be dropping it off at the local dealership on Tuesday when I get off of work, but if it's a potential easy fix, I'd just as soon do it myself then pay someone to do it for me. I've been a mechanic (professionally) for the past 7 years, but I'll admit that problems that occur under the dash aren't exactly in my field of expertise.

Might try replacing engine coolant temp sensor and connector. Probably original resin-tipped design sensor still in there. Usually cracks and sends info to PCM that engine is always cold. Though anything is possible. You want to replace with a brass-tipped sensor (this is a must for the S cars -- if it isn't an issue now, it eventually becomes one).

Sounds more like thermostat issue (stuck open). This would explain the coolant not getting up to temp and thus producing only lukewarm heat via the heater...

Derf

The thermostat and coolant temp sensor/connector fixed it. The heater blows nice and hot now. Thanks Derf.