I was frustrated with a heater on one of my cars that was either full hot or fully off. I thought it was a vacuum leak or a blown electromagnet pack, but it turned out simply that the little connector from the heater interior temp sensor was unplugged.

 

Correct without the information from the temp sensors the climate control "brain" does not know what to do. But when you select full hot full cold the brain is being told "I do not care what the temps are inside or outside just give me all you can ...."

 

Thanks for the info. That is on my short list of things to fix. Where would I find this connector?

 

H
My thoughts exactly......but I was thinking the outside temp sender.....I guess it defaults if either one is disconnected?

 

The temp sensors are in series. The end of one is connected to the beginning of the other, then goes to the 'control unit'.Either one disconnected will cause the same issue

 

The connector looks a lot like a full-size ATX hard drive power connector, it sits at or near your radio.