Failing A/C compressor resulting in poor mpg?

[vrt93]

So when I bought my truck around a year and a half ago, the PO stated that the AC was going to need some attention in the coming years, and recently I've noticed the compressor short cycling and the accumulator producing a ton of condensation when I run the AC. Since its been getting colder, I haven't been using the AC that much but I've just started to notice my fuel economy taking a hit when the AC is on. Could this be due to the compressor failing? I'm not an AC guru so I'm currently ascending the learning curve, and I plan on changing the compressor with a four seasons unit in the coming weeks anyway, but I figured I'd ask.

 

[Signal73]

Not sure on your location, but you are possibly into winter fuel at the pumps now which will usually deliver a MPG hit.

 

[vrt93]

I'm in Texas. I don't think its the fuel. When I drive with the ac off I get normal MPG. We just has a bit of a warm spell here so I had to start using the AC again for the first time in about a month and that's when I started noticing it

 

[Ozymandias]

It has an impact as it is a load on the engine.

You know that the AC is always on as soon as you dial the knob to a window (defrost) position - and that the AC indicator light does NOT come on in that mode.

 

[Wayne M.]

If your compressor is dragging the engine down that hard, you’d feel it if you were driving along, low load/ level road at a low speed like 35 mph. Do you? Do you get a herky jerky as the compressor cuts in/ out, like you’d feel in a 3 cyl Geo Metro?

 

[p-Bar]

are you feeling warm air coming out the passenger side vents? If so your low on freon.

 

[Tuesdak]

Bluntly it sounds like your AC is working fine with cycling and accumulator condensation "normal". The cycling may be because the in cab fan is set on low. Don't throw parts at it just because...(If anything it may be overcharged or, again, fine.)

The AC takes like 25 HP to run. Don't forget it may need to run the big engine cooling fan as well. Some small 4 banger diesels in the 80's didn't have enough power to run AC and get down the road with the inefficient R4 compressors of the day. So they weren't a factory option on em.

My 2003 with the NV5600 would drop MPG like a rock with the AC on: From 21 MPG to 16 MPG. Same with a new OEM Sanden compressor when the original failed at ~150K. I didn't buy a 1 ton for the MPG, but, it was interesting to see.