At startup I have heat. When driving it cools. I disconnect CCU I have heat at defrost so hot I open windows. I reconnect a different CCU. I test interior temp. sensor for resistence/ test ok. Temp sensor at heat exchanger behind ashtray is taped in so I disconnect electric connection/ hot at startup then cools whiles driving. I did not remove heat exchanger temp sensor and did not do resistence test yet!!! Could it be the heat exchanger temp sensor ?? Or what else might it be??? thanks for any advise
? does disconnecting CCU and having heat eliminate monovalve from consideration