I am having trouble with climate control system on my 78' 300D not always responding to current temperature conditions. I wanted to start out by checking the monovalve. For the 78 model I am suspecting that it is under the dash as it is not on the firewall by the battery as in the other pictures and posts that I have seen.

If it is cold in the morning, the heater usually comes on. If it is warm in the afternoon, the heater usually stays off. However, it seems like the valve is sticking at times.

Any suggestions welcome.

Don Dawkins

78' 300D