MY Son has a1995 ram 1500 with 318! Flushing radiator this morning I noticed heat wasn't getting hot and ac compressor was running? I had heat on in truck and running wide open ,it wasn't cold air but not hot either? I pulled relay on compressor and then heat was working correctly? When I put relay back on compressor comes on even though I have heat on climate control? I tried changing relay but same result? Any advice is welcome! Thanks

 

What did you have selected? Defrost? The temperature control has no impact on the compressor operation.

 

Yup. It is only which vents are selected. Any setting that includes defrost, will have the compressor running. I think any setting that includes the dash vents will also have the compressor running...... On the 97 and older trucks, it also depends on which way you turn the fan speed control ****. To the left will allow the compressor, to the right will only allow it in defrost/dash vent modes. (or something close to that.)

 

Thanks! I didn't realize the compressor would come on with fan turned to heat side but you are correct! When selector not on any type defrost compressor turns off! Thank you!

 

Yep. According to popular theory, refrigerated air carries less moisture than not.... (and that is indeed correct.) However, I figure that if I actually NEED "Defrost", then ALL the air is ALREADY 'refrigerated'.