New to TN need help with 90 4runner heater

[Rynosauce]

Hello everyone I need a little help. The heater in my 90 4runner runs hot and cold. While driving the heater runs warm to hot but when I slow down or stop the air goes cold. If I turn off the heater and then on again the air becomes hot. The only other noticeable thing was the temp gauge going from the middle to the H then back to the middle again, and this fluxuated back and forth all the way home but today that did not occur, only the hot cold air thing. My first thought is heater core or maybe the thermostat. Anybody got any suggestions?

[jetwhine]

Rynosauce,

You might want to think about replaceing your thermostat. That is a clasic problem with a stuck open t-stat.

[99blackSE]

T-stat is a cheap fix and is less time consuming too. I'd try that first.