Question about my A/C

[ExpeditionAndy]

For the most part my AC is working okay, but I notice that when I'm driving at a constant speed, regardless of whether it is highway or local road that the temp coming out of the vent when it's blowing on me it goes from cold to cool or maybe room temperature and then back to cold. When it does this cycling, it is almost as if the compressor is cycling on and off. It works fine and cools the vehicle but I was wondering if this is normal operation.

I have automatic AC in my '05 Expedition.

Thanks,

 

[69Hcode]

Probably a little low on Freon. The low side drops too much and the low pressure switch cuts the compressor off until the pressure raises back up.

 

[stamp11127]

All depends on the temp you have it set at. Set it as low as it will go and see if the cycling continues. If it still cycles then it is time to check the low and high side pressures.

 

[ExpeditionAndy]

All depends on the temp you have it set at. Set it as low as it will go and see if the cycling continues. If it still cycles then it is time to check the low and high side pressures.

I have it set at 72 degrees and it was 82 outside and the truck was outside all day but it was a cloudy day without a lot of sunshine.

 

[ExpeditionAndy]

Probably a little low on Freon. The low side drops too much and the low pressure switch cuts the compressor off until the pressure raises back up.

That is kind of what I was thinking (except the part of the LP switch - I hadn't gone that far with my thoughts). When I bought it last September it wasn't cooling quite enough and I had the dealership check it out. They said they evacuated and weighed in the correct charge and it worked okay until I switched to heating later in the fall. I assume with a vehicle of this age it probably has a slow leak somewhere in the system.

 

[IMINYOURCHAIR]

if you have the etac you will notice the temperature change sometimes if it is set higher than as low as it will go.

how is it doing when you have it set full low with the front/rear fans on high and the front in recirc? does it stay cool or does it still "cycle"?

 

[ExpeditionAndy]

I haven't tried that. I usually leave the temp set at 73 degrees. Now are days have turned cool and we do not need to run AC now. So I'll have to wait to see if we catch a hot day.

 

[IMINYOURCHAIR]

that'll work, also, if you do get a hot day, and it's still doing it even when ran on max cool, get the pressures checked that day, be sure it's hotter than 75 out so you get a good reading otherwise you will be waiting till spring.

I had to do a recharge on my truck for a compressor and hose replacement and didn't have a scale so I had to go by pressures, thing was, it was 70 out when I charged it, when it hit 90 out I noticed she was still short cycling and the low/high pressures had dropped a little, half a can undercharged due to temperature being too low.. everything has been fine since

 

[ExpeditionAndy]

Thanks! I'll post here once I have some definitive answers.