No Heat

[1991S13]

'91 240sx SE

Before today, my heater has worked great. This morning the car warmed up to normal temp, but when I turned the heater on it was just blowing cold air. I drove about 20 miles @ 60mph before it finally started blowing warm. Could this be air in the system, maybe a sticking valve somewhere, torn vacuum line, heater core problem...?

Thanks.

[yellow_jacket]

It could be one of several things. The most common is that the thermostat will stick open and the car will not warm up sufficiently. This shouldn't be your problem as you indicated that the carm warmed up all the way to where it did when it had good heat.

Second thing to look at is your coolant level. If there is insuffiecient coolant, it can starve the heater.

Third is to check for blockages in the lines. Easiest way to do this it to just feel the hoses when the car is warmed completely up. Should be hot the whole way to the heater core.

Last thing to check is going to be the control door. If for some reason the control door is nonfunctional, you won't be able to control the air temp. Sinc you said that it got warmer as you drove, this is probably not the case.

[1991S13]

Yeah, I don't think its the thermostat sticking - the car warmed up, and I just replaced the thermostat last winter.

Matter of fact, I just topped off the coolant Sunday when I serviced it. Checked today, and the level hasn't dropped at all.

I'll check the hoses tomorrow morning after I get to work, it will be good and warm by then plus I can pull it in the warm shop.

If it comes up again, I'll investigate the controls. Give my buddy at the salvage yard a call and pulling one shouldn't be too hard/expensive.

Thanks, I appreciate it.